Pop. Assessment Mid-Term Review

A systematic error in the design or conduct of study that leads to an erroneous association between exposure & the outcome:

BIAS

A systematic error in the design or conduct of study that leads to an erroneous association between exposure and outcome:

BIAS

Bar Graph:

Bars are separated to show each bar as a separate category -graphical representation of qualitative data Horizontal axis- we have the labels that are used for each of the classes Vertical axis- a frequency or relative frequency or percent Frequency scale can be used

Cultural Competence:

Be aware of unique characteristics within populations -social, political, and cultural factors can influence health policies and behaviors which will influence risk factors and health outcomes -important to be culturally aware in research and while utilizing research methods

Histogram:

Common graphical representation where the bars are together showing how the data classes relate to each other. Used for QUANTITATIVE DATA *unlike a bar graph, a histogram has NO natural separation between rectangles and adjacent classes

Eligible Population

Consists of those people who meet the criteria to actually participate in the study

Application of Ecological Model in PH:

Ecological Model: framework for determinants of health Ecological View: understanding health outcomes within that framework Ecological Approach: developing strategies to influence multiple levels or determinants

Alternative to an intent to treat analysis?

Efficacy analysis- which determines the treatment effects under IDEAL conditions such as when participants take the full treatment exactly as directed

Mortality-

Epidemiological definition for death

Morbidity:

Epidemiological term for disease or disability

Transient/Dynamic: condition that can be changed or altered

Ex: migration, deaths, grad students at USF

Fixed- permanent event or population

Ex: post-menopausal women (menopause is the fixed event)

Ecological Study

Examines the relationship between exposure and disease with population-level rather than individual level data

T/F: When considering incidence, it is important to count pre-existing cases.

FALSE

T/F: cross sectional studies can determine cause and effect

FALSE

T/F: Descriptive Epi tests hypothesis.

FALSE Descriptive Epi generates hypotheses vs. tests it

Precipitating Factors:

Factors that can trigger the onset of disease Ex: exposure to a disease or noxious agent

Enabling Factors:

Factors that facilitate or impede change/action Ex: low income, poor nutrition, bad housing or inadequate medical care may favor the development of disease Conversely, circumstances that assist in recovery or health maintenance may be enabling

Predisposing Factors

Factors that make one vulnerable/susceptible Ex: age, sex, genetic factors, or previous illness

Reinforcing Factors

Factors that reward or reinforce the behavior Ex: repeated exposure; undue work or stress may aggravate an established disease

Non-compliance:

Failure to observe the requirements of the protocol is known as non-compliance. This can happen in the treatment group, comparison group or both. Can also happen in any study design with participants. Negative side effects, loss of interest, desire to seek other therapies etc. could be potential reasons. * Noncompliance is problematic because it results in a smaller difference between the treatment and comparison groups than truly exists, thereby diluting the real effect of a treatment

T/F: Crude Rates can be compared across populations.

False; each population has different factors, characteristics, etc. Now, statistical software can account for those variations— this is down via a multi-variate analysis. Age is usually one of the largest things to be adjusted because of this.

Hippocrates-

Father of medicine Thought the 4 humors were do to an imbalance within the body leading to poor health (relationship between the body and emotions) Coined observation & the idea of looking at time, season, placement, and conditions in relation to disease.

Prevalence:

Frequency of existing disease 2 Types: Point Prevalence and Period Prevalence

Incidence:

Frequency of new cases of disease

Effect modification is similar to confounding BUT...

From an evaluation standpoint, like confounding, effect modification involves a 3rd variable and is evaluated using a stratified analysis, HOWEVER effect modification is a BIOLOGICAL PHENOMENON that cannot or should not be controlled. Rather, it should be carefully described

> means

GREATER THAN

2 Main Types of Matching related to Controls:

Group Matching & Individual Matching Group matching: final control group will match the final case group in terms of some characteristic

Ordinal data "ORDER"

Groups w/ quantitative order in degree, extent, or significance EX: greater than and less than—— pain rates as none, mild, or severe, rank of satisfaction etc. Ordinal values have a meaningful order BUT the intervals between the values on the scale may not be equal- EX: gap between 1st and 2nd place in a race may be small, whereas a larger gap occurs between 2nd and 3rd place. Ordinal data CAN BE GIVEN as frequencies

Ambidirectional Cohort Study

Has BOTH PROSPECTIVE & RETROSPECTIVE COMPONENTS * types of cohort studies depend on the research question or topic of study, time, money, and availability of suitable study populations and records

Ratio Data:

Has TRUE ZERO POINT ex: weight- 0 means there is No weight

WHO Health Definition (1946)

Health is a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.

Cohort Study:

Healthy subjects are defined according to their EXPOSURE STATUS and followed over time to determine the incidence of symptoms, disease, or death. The common characteristic for grouping subjects is their exposure level. 2 groups are compared: an exposed and an unexposed group. The unexposed group is called: reference, referent, or comparison group

Who developed the Theory of the Four Humors?

Hippocrates

Researchers who study the causes of disease prefer:

Incident cases b/c they are usually interested in the factors that lead to developing a disease rather than factors that affect its duration. Studies using prevalent cases must be interpreted cautiously because it is impossible to determine whether the exposure is related to the inception of the disease, it's duration, or a combination of the two

Timing of Cohorts:

Include- prospective, retrospective, and ambidirectional

Rate:

Includes TIME; Time is an intrinsic part of the denominator The term is often highly misused.

What is one of the most important measures of health in a country?

Infant Mortality Rate (IMR)

A type of bias that occurs when there is a differential level of accuracy in the information provided by the groups being compared:

Information Bias AND Recall Bias

What is the classic analytic approach for an Experimental study?

Intent to treat or treatment assignment analysis This type of analysis provides information on the effectiveness of a treatment under everyday practice conditions

3 sources for the Comparison Group in a Cohort Study:

Internal comparison group, the general population, and a comparison cohort

cohort study design

Is the term used to describe an epidemiological investigation that follows groups of people with common characteristics Other expressions that are used include: follow-up, incidence, or longitudinal study

A cohort study conducted in an open population:

Known as a dynamic population- is defined by exposures that CAN CHANGE overtime, such as cigarette smoking. Cohort studies in open populations may experience losses to follow up

< means

LESS THAN

Precision:

Lack of random error, which leads to false association between exposure and disease just by "chance," an uncontrollable force that seems to have no assignable cause

4 Data Classification Types:

N. O. I. R. Nominal Ordinal Interval Ratio

Confounding:

NOT A MISTAKE, but must be controlled; also not impacted by sample size; can be minimized/controlled for in the design and or analysis phases of the study

Confounding:

Not the fault of the investigator; Not on the causal pathway Effect of an extraneous third variable

Crude Mortality Rate

Number of deaths ÷ population total x 1,000 = _____ per 1,000

Overall Crude Mortality Rate

Number of people who died / population size at MIDYEAR

Scale Variables (think SPSS)

Numeric variables that are measuring quantity Ex: number of people or things, age, distance, weight, amount of $$ (QUANTITY, QUANTITY)

Quantitative Data:

Numerical info can be measured or identified on a number scale (ex: height or # of blisters) Can be discrete-variable can only take certain values like integers Continuous variable- can take on ANY value on an interval

Case Control Studies USE WHAT TO ANALYZE:

ODDS RATIO because there is no incidence information We essentially want to determine the odds of an exposure among the diseased compared to the odds of exposure among the non-diseased.

2 Types of Study Designs:

Observational or Experimental

Observational Study:

Observed without ANY interference by the investigator -Researchers are not manipulating any variables or giving a treatment or placebo Ex: cross sectional, cohort study, case control Observing 2 groups- Ex: Topic- one group who smokes, and one group who are non-smokers

Element (sampling unit):

One unit from a population upon which a measurement is taken

Descriptive Study:

Only summarizes and describes said outcome using descriptive statistics

Measure used in Descriptive Statistics:

PERSON- PLACE- TIME PERSON: characteristics are often evaluated to better understand disease- age, race, SES, gender, immune function etc. PLACE: high rates of skin cancer are in FL, place of exposure, place of food borne illness outbreak, etc TIME: years, months, days, hours, climate, seasonal variations etc

Prospective Cohort

Participants are grouped on the basis of a past or current exposure and are being followed INTO THE FUTURE to observe the outcomes of interest

Direct contact:

Pathogen survives best inside the body Ex: HIV, Herpesviruses, Ebola, etc.

Indirect contact:

Pathogen survives harsh environments Pick up pathogen from surface or air Ex: influenza, norovirus

Airborne:

Pathogens aerosolized & stay infective Ex: Influenza and Tuberculosis

Droplets:

Pathogens are in droplets but do NOT survive long this way Ex: Ebola, Bordetella Pertussis

Study:

People who agreed to participate

Period Prevalence

Period P: The # of existing cases divided by the # in the total population during a PERIOD of TIME.

Reason for Placebo Use:

Placebos permit study participants and investigators to be masked or unaware of the participants treatment assignment. Masking if subjects and investigators helps prevent bias ascertainment of the outcome, particularly when end points involve subjective assessments

Point Prevalence

Point P: The # of cases divided by the number in the total population at a POINT IN TIME

Analysis of Cohort-

Primary objective: is to compare the occurrence of symptoms, disease, and death in the exposed and unexposed. The occurrence of the outcome is usually measured using cumulative incidence or incidence rates and the relationship between the exposure and outcome is quantified using an absolute or relative difference between the risks or rates.

A cohort study CAN:

Provide more information on a large number of possible health effects, this type of study is preferable when little is known about the health consequence of exposure. A cohort is also efficient for investigating a RARE exposure, which is usually defined as a frequency less than 20%.

Luther Terry Surgeon General 1964

Published the "Surgeon Generals Report on Smoking" -the beginning of identifying tobacco's impact related to poor health outcomes—- created more research, saved approx. 8 million lives

Ordinal Values

Qualitative variables whose categories represent a level of the variable being measured Ex: satisfaction level, education level, rating scale questions, etc. ORDER

RR = 0.5 Means?

RR = 0.5, this means 0.5 times or 1/2 the risk of disease in exposed compared to unexposed

RR = 1.0 Means ?

RR = 1.0, this means NOOO ASSOCIATION between exposure & disease

RR = 1.6 Means?

RR = 1.6, this means 1.6 times the risk of the disease in the exposed compared to the unexposed or 60% increased risk of disease in the exposed (formula: 1.6 - 1.0 = .60 = 60%)

RR = 2.0 Means?

RR = 2.0, this means TWO TIMES the risk of disease in the exposed compared to the unexposed

Category Specific Rates:

Rates specific to some particular sub-population: age-specific, race-specific, sex-specific

Sampling design:

Refers to the method used to choose the sample from the population

Selection Bias:

Results from procedures used to select subjects into a study that lead to a result different from what would have been obtained from the entire population targeted for the study Most likely to occur in Case Control or Retrospective Cohort b/c exposure and outcome have occurred at time of study design Selection Bias can also occur in prospective cohort and experimental studies from differential loss to follow up because this impacts which subjects are "selected" for analysis

Cross- Sectional Study

"snapshot" of the population (picture and time of that day) - collect data at ONE point in time - surveys are often used - can collect information on multiple diseases and exposures at the same time

Attack Rate

# cases of disease that develop during a defined period / # in population at start of period *Usually used for infectious disease outbreaks Another form of Cumulative Incidence

Survival Rate

# living cases/ # cases of disease for a defined period of time

Incidence Rate (IR)

# new cases of disease in candidate population / person-time of observation (The measure is a true rate because time is directly integrated into the denominator)

Incidence Rate (IR)

# new health outcomes over time / total person time of observation PERSON-TIME IS IN THE DENOMINATOR YOU COUNT THE NUMBER OF NEW CASES OF DISEASE (numerator) / by the PERSON-TIME OF FOLLOW UP FOR EVERYONE IN THE STUDY

Case Fatality Rate (CFR)

# of deaths / # cases of disease for a defined period of time

Crude Incidence Rate:

# of new cases of disease divided by the # of the at risk population over a specific time period *FIXED POPULATIONS*

Incidence Rate (IR)

# of new cases of disease divided by the PERSON-TIME of the disease in an at risk population *DYNAMIC POPULATION*

Dr. John Snow

(1813-1858) English physician who used hand-drawn data layering on maps of London to identify and treat a cholera epidemic; Took off Broad Street Pump

Frameworks that Help Inform the Clinical Picture in Epidemiology:

* Epidemiological Triangle * Advanced Epidemiological Triangle * Life- Course Perspective * Socio-Ecological Model * Systems Thinking Approach

Cohort Study:

*Good for RARE EXPOSURE *Uses RELATIVE RISK (RR) *Can evaluate multiple outcomes *Loss to follow up is a problem *Uses NEW cases of disease (INCIDENCE) *3 Types of Cohort Studies: Prospective, Retrospective, & Ambidirectional *Better for identifying Temporal Sequence *Follows people over time

Case Control:

*Good for Rare Disease *Usually a rapid study *Good for diseases w/ LONG latency periods *Uses ODDS RATIO (OR) *Looks BACK to exposure (RETROSPECTIVE) *Can evaluate multiple exposures

Human to Human Transmission:

*direct contact *indirect contact *droplets *airborne *fecal-oral route

Risk Ratio:

- can only be calculated if you have information about incidence b/c incidence is what is USED TO CALCULATE RISK

Bias:

- primarily introduced by the investigator or study participants - can arise in ALL study types: experimental, cohort, case-control, etc. - occurs in the design and conduct of a study Can be evaluated but NOT fixed during the analysis phase. - bias does not mean that the investigation is prejudiced - 2 main types: selection and observation

Components of the Ecological Model:

- social/policy - community - institutional - interpersonal - individual/ interpersonal All of the above act in a dynamic way across the lifespan (Ranges from the macro to the micro level)

Concepts: advanced triangle of epidemiology

- the concept of "agent" is replaced w/ causative factors. This implies the need to identify multiple causes or etiologic factors of disease, disability, injury, and death. - The concept of "host" is replaced by a group or population & their characteristics. - The behavior, lifestyle factors, environmental causes, ecological elements, physical factors, and chronic diseases are taken into account along w/ the environmental concept to reflect the evolution from infectious disease to chronic disease. - Time accounts for the incubation periods, life expectancy, duration of the course of illness or condition.

Case-control study:

-Analytical study design w/ the purpose of identifying the cause of a disease -A group of individuals w/ a disease are compared to a group of individuals without the disease -ALSO CALLED RETROSPECTIVE STUDY because it starts w/ people who have the disease and looks backward for prior exposures which might be relevant to the development of the disease -Compares differences in exposures between two groups

Descriptive Study Designs:

-Do NOT assess disease etiology (causality) -Used to generate hypotheses -Describe the relationship between the exposure and the disease. -You cannot infer a causal relationship, but a firm hypothesis can still be generated. -Data from descriptive studies is used to allocate resources or plan programs. -Cannot infer causality.

Which technique can be used to control for confounding in the design of a study?

-Matching -Randomization -Restriction

Why is descriptive epidemiology helpful?

-Provides information about a disease or condition -Provides clues to identify a new disease or adverse health effect -Identifies the extent of the public health problem -Obtains a description of the public health problem that can be easily communicated -Identifies the population at greatest risk -Assists in planning and resource allocation -Identifies avenues for future research

Ecological Studies:

-Similar to cross-sectional studies except the study is conducted on population data NOT individual data -compare an outcome with an exposure using summary data

Bradford Hill Criteria for Causality is useful for:

-critically reading epidemiological studies -designing epidemiological studies -interpreting the results of your own studies

Qualitative Data:

-descriptive info/data -describes something Ex: gender, ethnicity, nominal or ordinal level Ex: average, above average, poor, below average = describing treatment services at TGH

Limitations of Case-Control Studies

-does not measure incidence -subject to recall bias -difficult to identify temporal sequence -can only look at one outcome

Ecological Model

-emphasizes the importance of the social and physical environment that strongly shape patterns of disease and injury as well as our responses to them over the entire life cycle" (direct quote)

Benefits of Case-Control:

-feasible for rare disease w/ long time periods between exposure and disease -ask people about PAST events -ask people about MANY exposures -rapid -inexpensive -can evaluate multiple exposures -useful when we do not have any idea about the cause of the disease -good for diseases with long latency periods

Main Characteristics of Controls:

-ideally controls are people who would have been selected as cases if they had the disease -there should be NO association between the selection of controls and the exposure because if controls have an increased risk of exposure from some other factor, we may miss an association between cases and controls Controls serve to give us an estimate of what the usual exposure is.

Public Health mission:

-investigative -research oriented -multi-disciplinary -constantly evolving

Experimental Study:

-investigator controls the experimental environment in which the hypothesis is tested Ex: Randomized, Double Blind Clinical Trial is the gold standard Purpose: to obtain the most definitive evidence that a treatment causes a response (often used to test Cause/Effect hypothesis)

Measures of Location (center):

-mean -median -mode -percentiles -quartiles

Role of Epidemiology in Public Health:

-monitor health of a population -respond to emerging PH problems -promote research & use of evidence based interventions -evaluate the effectiveness of interventions -findings provide foundations for PH policy -set funding priorities for research & intervention programs

How are Descriptive Statistics obtained for Epi ?

-pre-existing data -vital records (birth and death certificates) -reportable diseases from surveillance programs or disease registries -national surveys -information on the internet from past studies -self-collected data from research studies

Descriptive Epidemiology:

-provides information on disease patterns by considering various characteristics of PERSON, PLACE & TIME -describes a health situation vs. determining a causative factor -Types of Descriptive Epi.: Case Series, Ecological, & Cross Sectional -Descriptive Studies: hypothesis generating vs. hypothesis testing

Measures of Variability (spread)

-range -interquartile range -variance -standard deviation -coefficient of variation

Common Sampling Methods:

-simple random sample (SRS) -convenience sample -systematic sample -cluster sample -stratified sample

Public Health Components:

-surveillance -monitoring -analysis -outbreaks -epidemics -disease prevention -communication -risk -research -health promotion

Ken Rothman's Causal Pies:

-theory of causation -useful when looking at diseases w/multiple causes (chronic conditions— genetic conditions) 3 Types of Causal Factors: *sufficient *component *necessary With few exceptions, MOST diseases are caused by multiple risk factors known as: component causes of Disease

Disease Frequency IMPORTANT:

-want to quantify disease occurrence in a population Measures should take into account: *Number of individuals affected with the disease *Size of source population *Length of time the population was followed

What was the theory of the four humors?

1. Blood 2. Yellow bile 3. Black bile 4. Phlegm

Where to find controls? 3 general groups:

1. General Population Controls: -those obtained through getting a random sample of the Gen. population from which the cases were derived from 2. Other Hospital Patients: 3. Special Controls- such as friends or relatives

Measures of Disease Frequency should take into account:

1. Number of individuals affected with the disease 2. Size of source population 3. Length of time the population was followed

4 Essential Skills of Population Assessment:

1.) Assessment 2.) Cause 3.) Clinical Picture 4.) Evaluation

3 Threats to Validity:

1.) Bias 2.) Chance 3.) Confounding

5 main ways to summarize qualitative data:

1.) Frequency Distribution 2.) Relative Frequency 3.) Percent Frequency Distribution 4.) Bar Graph 5.) Pie Chart

Aging is affected by 5 variables:

1.) Human Development and aging are lifelong processes (life is on a continuum) 2.) Historical Time and Place (where you live impacts subsequent events) 3.) Timing (year and decade in which you were born influences life events) 4.) Linked Lives (we are all linked together) 5.) Human Agency (ability to choose, perceive, & act based on the opportunities presented)

3 Key Factors of Incidence:

1.) Measures new disease events 2.) New cases are measured from the "at risk population" 3.) Takes into account the specific amount of time that the population must be followed until they develop the disease

Assessing & Determining Cause:

1.) Primary Determinants 2.) Mode of Transmission 3.) Chain of Causation 3 constructs- disease transmission, chain of infection, incubation periods

Koch's Postulates:

1.) The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms. 2.) The microorganism must be isolated from a diseased organism and grown in pure culture. 3.) The cultured microorganism should cause disease when introduced into a healthy organism. 4.) The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

Clinical Picture Tells us:

1.) Who is susceptible? 2.) What type of exposure? 3.) What are the pathological changes? 4.) What are the symptoms? 5.) What are the Possible outcomes?

Quantitative Data- 5 ways to summarize data

1.) frequency distribution 2.) relative frequency and percent frequency 3.) Dot Plot 4.) Histogram 5.) Cumulative distributions

3 Things to carefully consider when Assessing Populations:

1.) number of people 2.) size of population 3.) length of time

When did Healthy People start?

1990

Chain of infection:

1st Link: Pathogen/Infectious Agent 2nd Link: Reservoir 3rd Link: Portal of Exit 4th Link: Mode of Transmission 5th Link: Portal of Entry 6th Link: New Susceptible Host

When is a sample considered representative?

A sample is considered representative of a population from which it is drawn if every element of the population has equal chance of being included in the sample

Equipoise:

A state of mind characterized by legitimate uncertainty or indecision as to choice or course of action AKA- there must be genuine confidence that a treatment may be worthwhile to administer it to some individuals and genuine reservations about the treatment to withhold it from others

Hill Criteria for Causality: Strength

A strong association is more likely to be causal. The measure of strength of an association is the relative risk and not statistical significance.

Cross- Sectional Study

A study in which a representative cross section of the population is tested or surveyed at one specific time. KEY COMPONENTS: -identify participants because they represent a certain group -information on exposure and outcome are collected at the same time -BUT NOT SELECTED based on exposure or outcome

Frequency Distribution:

A tabular summary of data showing the frequency of number of items in each of several non-overlapping classes (like groups)

Cohort Study:

A type of epidemiologic study where a group of exposed individuals (individuals who have been exposed to the potential risk factor) and a group of non-exposed individuals are followed over time to determine the incidence of disease

Cohort Study

A type of epidemiologic study where a group of exposed individuals (individuals who have been exposed to the potential risk factor) and a group of non-exposed individuals are followed over time to determine the incidence of disease SUBJECTS ARE PICKED ON THE BASIS OF EXPOSURE Picks SUBJECTS BASED ON EXPOSURE TO IDENTIFY IF THE INCIDENCE OF THE DISEASE WILL SURFACE IN THE EXPOSED AND UNEXPOSED GROUP

Case-control study

A type of epidemiologic study where a group of individuals with the diseases, referred to as cases, are compared to individuals without the disease, referred to as Controls Good for: identifying possible risk factors as you can ask about many different exposures and you look BACK IN TIME TO SEE WHAT HAPPENED

Rate

A type of ratio; Differs from a proportion because the denominator involves a measure of time. Epidemiological rates are composed of a numerator (the number of events such as health outcomes), a denominator (a population in which the events occur), and a measure of time. The measure of time is the time period during which events in the numerator occur. The denominator consists of the average population in which the events occurred during the same time period.

Epi measures (considering frequency)-

A/B Numerator: number w/the condition of interest—— the measure of people with a given health condition Denominator: population from which the numerator is being measured —— often based off of the case-definition (number of births or deaths, number of people with arthritis, number of people w/ malaria, etc.)

In the definition of epidemiology "determinants" generally include:

AGENTS CAUSES RISK FACTORS SOURCES

General Transmission:

Abiotic environmental factors- wind, water, inhalation of spores, entry into skin Animal vectors- fleas bubonic plague Mosquitos- malaria & dengue

In general, how many controls per case is needed and why is it important?

About 4-5 controls for each case to maximize power and maximizes the sample size.

Interval Data

Adds info on how much more; does NOT HAVE A TRUE ZERO point, 0 does not indicate absence of attribute

Subsets of Mortality Rates:

Age specific, proportionate, and disease specific

Randomization:

An act of assigning or ordering groups that is the result of a random process -Preferred method for assigning the treatments because it is less prone to bias than other methods and it produces groups with very similar characteristics if the study size is sufficient

Hill Criteria for Causality: Plausibility

An association is more likely to be causal when it is biologically plausible.

Hill Criteria for Causality: Consistency

An association is more likely to be causal when it is observed in different population groups

Observation/Information Bias:

An error arising from systematic differences in the way information on exposure or disease is obtained from study groups (Also KNOWN AS INFORMATION BIAS) Results in participants who are incorrectly classified as either exposed or unexposed or diseased or not diseased Occurs after subjects have entered the study Several types of Observation Bias: recall bias, interviewer, differential and non-differential misclassification

Bias:

An error committed by the INVESTIGATOR in the design or conduct of a study that leads to a false association between the exposure and disease

Miasma Theory of Disease

An obsolete medical theory that held that diseases such as, cholera, chlamydia, or Black Death were caused by "Miasma"- a form of noxious bad air (sometimes called night air). Theory held that epidemics were caused by miasma emanating from rotting organic matter or bad air ... air pollution. The theory was wrong.. but it did lead to the development of Germ Theory.

Control/Comparison Group in an Experimental Study:

The group that does NOT receive the agent under study. Depending on the purpose of the trail, this group may receive: no treatment, an inactive treatment or placebo, or another active treatment.

Treatment Group in an Experimental Study:

The group that receives the agent under study

Causality History- "Spontaneous Generation"

The idea that living organisms can suddenly appear w/o decent from similar organisms. It was believed that certain forms such as fleas could arise from inanimate matter such as dust or that maggots could arise from dead flesh.

Crude Mortality Rate (CMR)

The mortality rate from all causes of death for a population.

Cumulative Incidence (CI)

The number of new cases of a disease during a specified time period divided by the total number of people at risk; the proportion of new cases of a disease in a population.

Cumulative Incidence (CI)

The number of new cases of a disease during a specified time period divided by the total number of people at risk; the proportion of new cases of a disease in a population. Used for relatively stable populations, where it can be assumed that everyone is followed for the same time period

Proportion:

The numerator is a subset of the denominator; often expressed as a percentage

Source Population:

The population from which our study sample can be drawn

Epidemiology:

The study (scientific, systematic, & data driven) of the DISTRIBUTION (frequency, pattern) & DETERMINANTS (causes, risk factors) of health- related to states & events (not just diseases) in specified populations (neighborhoods, schools, cities, state, country, global).

Population Assessment:

The study of the DISTRIBUTION and DETERMINANTS of death, disease, and disability in human populations, and the application of this study to control health problems.

Epidemiology:

The study of the distribution and determinants of death, disease, and disability in human populations

Incubation Periods:

The time elapsed between exposure to a pathogenic organism & when symptoms and signs become apparent Stage of Susceptibility (exposure) Stage of Subclinical Disease (pathological changes occur) Stage of Clinical Disease (onset of symptoms- also usual time of diagnosis) Stage of Recovery, Disability, or Death

Incubation Period:

The time elapsed between exposure to a pathogenic organism and when symptoms and signs become apparent Stage of Susceptibility: exposure Stage of Subclinical Disease: pathological changes Stage of Clinical Disease: onset of symptoms; usual time of diagnosis Stage of Recovery, disability, or death

Infant Mortality Rate (IMR)

The total number of deaths in a year among infants under 1 year old for every 1,000 live births within a year in a society.

Infant Mortality Rate (IMR)

The total number of deaths in a year among infants under one year of age for every 1,000 live births in a society.

Ecological Study:

The unit of analysis in ecological studies is populations not individuals Looks at rates of exposure and disease compared across populations as opposed to using individual data Type of Descriptive Study

Causality History- "Miasmas"

Theory held that diseases such as cholera, chlamydia, or the Black Death were caused by a miasma, a noxious form of "bad air," also known as "night air." Theory held that the origin of epidemics was due to a miasma, emanating from rotten organic matter.

Case Series:

larger collection of cases of disease, often grouped consecutively and listing common features such as the characteristics of affected patients

Cluster Sample:

population is split into parts or clusters usually based on geography and then entire clusters are selected randomly and sampled

Relationship between Incidence & Prevalence:

prevalence = incidence x duration Duration refers to the length of a disease from onset to its termination by either cure or death. If incidence is low and duration is LONG the prevalence will be relatively high. But.. if incidence is high but duration is short, prevalence will be relatively low. This relationship only holds up if the duration of disease remains constant.

Nominal Variables:

qualitative variables whose categories have no natural ordering or ranking; Ex: sex, race, gender, district, religious affiliation, country etc. (NAME- categories)

Two main types of Bias:

selection bias and information bias

Belmont Report (1979)

summarizes the basic ethical principles and guidelines for the protection of human subjects of research. (Respect for persons, beneficence and justice)

Causality History- "Germ Theory"

Theory of disease states that some diseases are caused by microorganisms. These small organisms, too small to see w/o magnification, invade: animals, humans, and other living hosts. Their growth & reproduction within their hosts can cause a disease. Beginning of Modern Medicine- discovered by Louis Pasteur 1 Central Theory : 1 microorganisms causes one disease — most revolutionary concepts in medicine.

What does a long induction and latent period mean?

There is a long time between the causal action of an exposure and the eventual diagnosis of disease.

Main limitation of Ecological Study:

These studies are primarily using already available data previously collected for other reasons. Without individual data, one cannot be certain that those individuals with the exposure HAVE the outcome.

Cause- Specific Mortality Rate (CSMR)

the death rate due to a particular disease or specific cause

Death Rates/Mortality/Fatality Rates

the number of deaths per a given population *again the denominator usually uses 1,000 Different denominators might be used if looking at a rarer death rate Ex: Maternal Mortality Rate: the number of deaths due to childbirth- we usually use 100,000 people in the denominator since this is a relatively rare cause of death

Case Reports:

accounts of a single occurrence of a noteworthy health-related incident or small collection of such events

Hill Criteria for Causality: Gradient

This criterion refers to the presence of an exposure-response relationship. If the frequency or intensity of the outcome increases when an exposure is more intense or lasts longer, then it is more likely that the association is causal.

Advances in neonatology in the early 2000s led to a decrease in the number of deaths due to preterm birth but had little impact on mortality due to congenital anomalies (birth defects). Yet, there was an increase in the % of deaths due to birth defects during that same time period. What is the most logical reason for this increase?

This is a PROPORTIONATE MORTALITY RATE and the increase is due to the decrease proportion of preterm births.

Weak Associations are defined as:

Those with odds ratios less than 1.5

Traditional Epi. Triangle:

Time- (middle of triangle) Agent- (peak of the triangle) Host- (left corner of triangle) Environment- (right corner of triangle) Used for communicable disease, basic foundation to all of Epidemiology. However, infectious/communicable disease is no longer the leading cause of death in industrialized nations. Therefore a more advanced model is now needed.

Advanced Epi. Triangle:

Time- (middle/center of triangle) Causative Factors- (top or peak of triangle) Group Population & their Characteristics- (left corner of triangle) Environment, Behavior, Cultural, Physiological Factors & Ecological Elements- (right corner of triangle) * This new model mirrors the more complex medical models and incorporates the broader scope of chronic disease and genetic disorders. * Recognizes the wide range of elements which cause disease in populations. * Reflects Behavior and Culture of a community to mitigate non-infectious diseases. * Neither the traditional Epi. Triangle or the Advanced Epi. Triangle is complete or comprehensive.

Live Birth Rate

Total number of live births per 1,000 population; usually expressed for a 1 year period Generally the denominator uses 1,000 for the birth rate. However, when looking at specific birth rates (ex: number of adolescent births- we would use the number of adolescent women in the denominator)

Case Control:

Traditionally viewed inferior to the Cohort Study; Subjects are selected on the basis of whether they have or do not have the disease; Individuals who have the disease are called CASES Individuals who do NOT have the disease are called CONTROLS Exposure histories of cases and controls are obtained and compared.

Fecal-Oral Route

Transmitted through contaminated water or food Ex: cholera, norovirus, shigella

Analytical Study:

Tries to answer how or why a certain outcome might occur

T/F: Stratified =homogeneous Clusters =heterogeneous

True

T/F: Randomization minimizes BIAS (increases accuracy) Replication minimizes random sampling variation (increases precision)

True

T/F: "Controls" in Case- Control studies ideally are those individuals who would have been cases if they had gotten the disease

True

T/F: A confounding variable MUST be associated w/ the exposure of interest and the disease under study among both exposed and unexposed individuals.

True

T/F: A rate is like a proportion, but time is also involved.

True

T/F: A sample is more appropriate to be used for a study.

True

T/F: ALL descriptive studies are observational.

True

T/F: Age is one of the most important predictors of disease.

True

T/F: Analytical Studies can be both observational and interventional.

True

T/F: Because researchers universally agree on the importance of Temporal Sequence, this is why cohort studies are considered stronger in identifying causality.

True

T/F: Case definitions can change over time.

True

T/F: Confounding is not in the causal pathway.

True

T/F: Cumulative Incidence (CI) can only be calculated from a closed or fixed population. Meaning, you MUST have complete follow up on each person. However, calculating incidence in a dynamic population is possible via Incidence Density and using person-time.

True

T/F: Cumulative Incidence (CI) used mainly for fixed populations b/c it assumes that everyone is followed for the entire study period.

True

T/F: Ideally, case definitions are very sensitive.

True

T/F: In a proportion the numerator is a subset of the denominator.

True

T/F: Incidence Rate (IR) typically used for transient populations (true rate).

True

T/F: It is extremely IMPORTANT that the selected sample for the study, be representative of the population because this ensures good study results

True

T/F: Prevalence is a proportion.

True

T/F: Relative Freq. Always totals to 100 Percent Freq. Always totals to 100%

True

T/F: Samples are used to make inferences about the population.

True

T/F: Studies involving incident cases take longer to conduct as you need to wait for new cases to develop.

True

T/F: When looking at Incidence cases, we use something called relative risk or "RISK" to measure the risk in new cases of a disease. This is done in a cohort study.

True

T/F: sample = statistic Population = parameter

True

T/F: the Marine Hospital Service of 1978 became the U.S. PH Service in 1912.

True

True/False: A proportion ranges from 0-1.

True

True/False: No matter what, there will always be some degree of sampling error.

True

True/False: To calculate incidence in a dynamic population, we use the concept of person-time. Calculating Incidence in a Dynamic Population can be done via Incidence Density.

True

T/F: A census should not be used for studies.

True- *not accurate *expensive *impossible *not everyone is accounted for (ex. Criminals, migrant workers etc)

T/F: Confounding is a problem of comparison.

True.

T/F: Age is generally the most important factor to consider.

True; 2 ways to calculate age adjusted rates: Direct Age Adjustment Indirect Age Adjustment using Standardized Mortality Ratio (SMR)

Cumulative Incidence Range and Uses:

Type: Proportion Range: 0 to 1 Numerator: new cases Denominator: population at risk Uses: research on causes, prevention, and treatment of disease

Prevalence Range and Uses:

Type: Proportion Range: 0 to 1 Numerator: existing cases Denominator: total population Uses: resource allocation and planning etc

Incidence Rate Range and Uses:

Type: True Rate Range: 0 to infinity Numerator: new cases Denominator: Person-Time at risk Uses: Research on causes, prevention, and treatment of disease

Cohort Study

Typically Examines multiple health effects of an EXPOSURE; subjects ARE DEFINED ACCORDING TO THEIR EXPOSURE LEVELS AND FOLLOWED FOR DISEASE OCCURRENCE

Case-Control Study

Typically examines multiple exposures in relation to a disease; subjects are defined as CASES & CONTROLS, and exposure histories are compared

Cross-Sectional Study

Typically examines the relationship between EXPOSURE AND DISEASE PREVALENCE in a defined population AT A SINGLE POINT IN TIME

Bias

Unintended mistake of the researcher; NOT lessened or otherwise affected by sample size; often must prevent/minimize at the design stage because control during analysis is difficult or impossible

Jacobson v. Massachusetts (1905)

Use of police power; small pox debate of compulsory vaccinations; state has authority to enact laws related to PH matters

Closed cohort:

Used to describe a FIXED COHORT with no losses to follow up

Why are rates important in epidemiology?

Used to measure risks associated with exposures and provide information about the speed of disease development Used to make comparisons among populations

In the definition of epidemiology "distribution" refers to:

WHO WHEN WHERE DISTRIBUTION is about a frequency or a pattern, so who, when & where. Distribution does NOT refer to WHY.

Odds Ratio (OR): (also known as relative risk *RR*)

We don't have that risk or that incidence information, so we are calculating the odds of a particular outcome happening given that exposure vs. an incidence of an outcome given no exposure. To calculate RR, you must have INCIDENCE or new case information and you need information about the population at risk. Typically in a case-control study, you won't be able to calculate risk ratio. With RR calculations, YOURE thinking about the "RISK" of developing our outcome of interest, so you're looking into the future. With Case-Control studies were looking backwards (retrospect) because we already have our outcome of interest, but we are calculating the ODDS of that happening based on potential exposures. Looking forward: =risk of developing Looking backwards= ODDS of developing

Hill Criteria for Causality: Specificity

When an exposure is associated with a specific outcome only (for example, a cancer site or even better a particular histological type of this cancer), then it is more likely to be causal. There are exceptions, however, for example, smoking causing several forms of cancer.

Why is culture important?

When culture is ignored, families are at risk of not getting the support they need, or worse yet, receiving assistance that is more harmful than helpful -Culture is a filter through which people process their experiences and events of their lives -It influences people's values, actions, and expectations of themselves -it impacts people's perceptions, and expectations of others

Fixed Cohort:

When the cohort is formed on the basis of an irrevocable event, such as undergoing a medical procedure, giving birth etc. Thus, the individuals exposure is fixed and does not change over time

Effect modification-

When the magnitude of the effect of an exposure differs depending on the level of a third variable

Non-Probability Sample

any sample in which little or no attempt is made to get a representative cross section of the population -elements do NOT have an equal chance of being included in the sample -NON- RANDOM Ex: convenience sample, snowball /quota

Web of Causation Model

illustrates the complexity of relationships; Disease NEVER depends upon a single isolated cause, rather it develops from a chain of causation in which each link itself is a result of complex interaction of preceding events

Ratio:

You divide one number by another, but there does not need to be any relationship between the two numbers (the numerator is NOTTTT a subset of the denominator)

Attack Rate

incidence rate calculated for a particular population for a single disease outbreak; expressed as a percentage Formula: # of cases of disease that develop during a defined period/ # in the population at risk at start of period Used when studying outbreaks- morbidity in food borne outbreaks etc

Strengths and Limitations of Cross- Sectional

Strengths: -Ability to identify prevalence of disease or exposure -Useful for determining Heath care needs -Fairly rapid study -Usually pretty inexpensive Limitations: -We are identifying prevalent cases so we cannot be sure if the disease occurred prior to the exposure -Those who died quickly would not be less likely to be in the study so we may be identifying an association between the exposure and disease survival -hypothesis generating -results from this study would lead to the need of additional analytical studies

Health-Related Quality of Life (HRQoL)

a multidimensional concept that focuses on the impact health status has on physical, mental, emotional, and social function and quality of life overall

Interval/Ratio:

"Scale- continuous in SPSS" Most PRECISE LEVEL of measurement, label includes things that can be measured rather than classified or ordered Known as: scale, quantitative or parametric, can be discrete w/ whole numbers or continuous w/fractional numbers

Situational Ethical Framework:

"The end justifies the means" - ethics of a behavior depends on the end result or situation Ex: Killing someone on death row, assisted suicide, war, etc. is okay.

Louis Pasteur (1822-1895)

A French chemist, this man discovered that heat could kill bacteria that otherwise spoiled liquids including milk, wine, and beer. Identified germs as causes of disease which led to prevention principles of vaccination, fermentation, and pasteurization; saved many lives during this discovery

Hill Criteria for Causality: Coherence

A cause and effect interpretation of an association should NOT conflict with what is known about the natural history and biology of disease, or its distribution in time and place.

Hill Criteria for Causality: Temporality

A cause should not only precede the outcome (disease), but also the timing of the exposure should be compatible with the latency period (in non-infectious diseases) or the incubation period (in infectious diseases).

Relative Frequency:

A class where the fraction or proportion of the TOTAL number of data items belonging to the class

Pie Chart:

A commonly used graphical representation for presenting RELATIVE FREQUENCY distributions for QUALITATIVE data

Population vs. Census

A complete count or enumeration of the population *Every member of the population is included in the census

Necessary Cause (Rothman's Causal Pies):

A component cause that is a member of every sufficient cause

Definition of Confounding-

A distortion between exposure and disease is distorted because it is MIXED with the effect of another factor that is associated with the disease It is a MIXING OF EFFECTS between the association of exposure and disease. Occurs because it is mixed w/the effect of another factor associated with the disease -confounding is a problem of comparison, a problem that arises when important extraneous factors are differently distributed across the groups being compared

Population:

A group w/ common characteristics in terms of PERSON, PLACE & TIME

Age Specific Mortality Rate (ASMR)

A mortality rate limited to a particular age group. The numerator is the number of deaths in that age group; the denominator is the number of persons in that age group in the population.

Percentage

A proportion that has been multiplied by 100 Ex: the percentage of male deaths from AIDS was (0.83 * 100) = 83% A proportion indicates how important a health outcome is relative to the size of the group.

Randomized Clinical Trial (RCT)

A research design that has at least two groups-a treatment group and a control group (usually a placebo control)-to which participants are randomly assigned. Study to evaluate the effect of treatment. Outcome is compared between two groups.

Component Cause (Rothman's Causal Pies):

Any one set of conditions which are necessary for the completion of a sufficient cause (this is a PIECE of the pie) With few exceptions, MOST diseases are caused by multiple risk factors known as component causes of disease

System's Thinking:

Approaching complex health systems w/ a systems perspective helps build programs and policies that are aware of and prepared for unintended consequences -viewing how all things are connected together -system dynamics, complexity science Bob Williams Concepts: * interrelationships * perspectives * boundaries

Case Control Studies are Preferable WHEN:

Are preferred when little is known about the etiology (cause) of a disease b/c they can provide information on a large number of possible risk factors. They take less time and cost less money than cohorts primarily b/c the control group is a sample of the source population. Case control studies are more efficient than cohort studies for studying rare diseases because fewer studies are needed and for studying diseases with long induction and latency periods because long term prospective follow up is avoided

Convenience Sample:

Ask people near by, people walking into a shopping center -often biased -quick -easy / CONVENIENT -cheap -SELF SELECTION BIAS

4 Essential Skills in Population Assessment:

Assessment: *disease frequency *disease distribution Assessing Disease Frequency: *quantification of MMD in the population *How often does the MMD occur in the population?

Approaches to Loss to Follow Up:

Best strategy to use when participants do NOT initially respond is to send additional mailings When participants are truly lost to follow up, investigators employ a # of strategies: sending letter to last known addresses w/ "Address Correction requested," check telephone directories, directory assistance, internet resources, whitepages.com, voter registration, contact relatives and friends and physicians identified at baseline.

Retrospective Cohort Study:

Both the exposure and outcomes have ALREADY occurred when the study begins. Thus, this type of investigation studies only prior NOT future outcomes

Socio-ecological model

Bottom: individual (knowledge, attitudes, skills, culture), interpersonal (families, friends, social networks) , organizational (organizations, social institutions), community (relationships between orgs), public policy(National, state, local laws, regulations) -TOP

Because of their relatively small sample size, what study is preferred when the exposure data are difficult or expensive to obtain?

CASE CONTROL- Also desirable when the population under study is DYNAMIC because it is difficult to keep track of a population that is constantly changing

Odds Ratio (OR) is commonly used in which study design?

CASE- CONTROL Note- can be used in cross-sectional & cohort as well

Relative Risk, Risk Ratio, or Rate Ratio is *most commonly* used in what study design?

COHORT Study Design

Before identifying Cases you develop a ________ _______________.

Case definition

Systematic Sample:

Choose a starting value at random. Then choose every kth member of the population. -listing method -easier to administer than Simple Random Sample

descriptive statistics

Collecting, summarizing, organizing, and displaying/presenting data

Internal Comparison Group for Cohort:

Consists of unexposed members of the same cohort -should be used whenever possible b/c it's characteristics will be the most similar to the exposed group General Population- used for comparison when it is not possible to find a comparable internal comparison group. Based on pre-existing population data on disease incidence and mortality. Comparison Cohort- consists of members from another cohort; least desirable option b/c a comparison cohort although NOT exposed to the exposure under study, is often exposed to other potentially harmful substances therefore results can be hard to interpret

In a Case Control Study, to select Controls:

Controls are a SAMPLE of the population that produced the CASES. The guiding principle for the valid selection of controls is that they come from the same base population as the cases. If this condition is MET, then a member of the control group who gets the disease under study would end up as a case in the study. This is KNOWN AS: "the would criterion" and its fulfillment is CRUCIAL to the VALIDITY of a Case Control Study. Also- controls must be sampled independently of exposure status. Meaning, exposed and unexposed controls should have the same probability of selection

Number of new cases / number in the candidate population

Cumulative Incidence

Number of New Cases / Number in Candidate Population

Cumulative Incidence (CI)

2 Ways to Measure Incidence:

Cumulative Incidence (CI) & Incidence Rate (IR)

What does the abbreviation DDD stand for?

DDD= disease, death, disability

Distribution or Determinant? Compare food histories between persons with gastrointestinal illness and those without.

DETERMINANT

Distribution or Determinant? Graph the number of cases of meningococcal meningitis by year for the state of FL:

DISTRIBUTION

Distribution or Determinant? Mark on a map the residences of all children born with birth defects within 2 miles of a hazardous waste site.

DISTRIBUTION

Discrete Data:

Data Can only be discrete values such as count or integers and can be listed or placed in order

Continuous Data:

Data can be ANY value on an interval scale

Cohort

Defined as a group of people with a common characteristic or experience

Validity

Defined as the lack of bias and confounding. Bias is an error committed by the investigator in the design or conduct of a study that leads to a false association between the exposure and disease.

Important considerations to the expression of epidemiological measures:

Defining the numerator: -Case Definition (condition)- For epidemiologic measures to be valid, the case of disease or other health phenomenon being studied MUST be defined carefully and in a manner that can be replicated by others -Frequency- How many cases are there? -Severity- Some Epi. Measures employ morbidity as the numerator and others use mortality Defining the denominator: -Does the measure make use of the entire population or a subset of the population? Some measures use the "population at risk," defined as those members of the population who are capable of developing a disease, for example, people who are NOT immune to an infectious disease Existing: -ALL cases vs. NEW cases

2 Types of Study Designs:

Descriptive & Analytical

Compare one group to another: Determinant or Distribution

Determinants- look at causes, agents, and risk factors Distributions- DONT likely compare. They just try to determine the WHO, WHAT, WHERE, or FREQUENCY. It's more of "how many" vs. comparison of histories. Counting, determining patterns, frequency etc.

Case Crossover Design

Developed for situations when brief exposure causes a transient change in the risk of a rare acute onset of disease. Were exposures immediately preceding the event different from those exposures which usually occur? Each person serves as his/her own control. A person's time is divided into index period (case) and a reference period (control)

Robert Koch

Developed the culture plate method to identify pathogens; Established the 4 criteria regarding causative factors related to microbes and disease, identified vibrio that caused cholera (approx. 20 years later after Snow) Famous for discovering / isolating TB bacterium

Descriptive Epidemiology:

Hypothesis generating Often used earlier in the investigation of an exposure or disease Two common designs: cross-sectional & ecological——- also include case studies and case series

inferential statistics

Hypothesis testing, determining relationships, and making predictions

Box & Whisker Plots:

Identify 5 Key Data Points: -minimum -maximum Q1 (25%) Q2 (50%) also known as the median Q3 (75%)

3 Goals of Research Studies:

Identify significant associations that can be used to prevent disease Evaluate Intervention Programs Determine the effectiveness of medical treatments and procedures

Hill's Criteria of Causality: Experimental Evidence

If experimental evidence exists, then the association is more likely to be causal. Such evidence, however, is seldom available in human populations.

Disability- umbrella term for:

Impairments Activity limitations Participation Restrictions

What are the 2 measures to assess disease frequency?

Incidence & prevalence

Types of "Incidence":

Incidence Rate (IR) Cumulative Incidence (CI) Incidence Density Attack Rate

Sampling Frame:

Listing of elements in a population from which a sample is chosen

Case Definitions come from:

Lists of symptoms Laboratory tests Physician diagnosis Autopsy Self-reported data Medical record review Obtained on a survey

What does the abbreviation MMD stand for?

MMD= morbidity, mortality, disability

Most common summary measures:

Mean, median, and standard deviation

Chance:

Merely random variation; as we increase the sample size of the study the impact of chance diminishes

Disease Transmission:

Modes of infectious disease transmission

10th Amendment of the U.S. Constitution says who is in charge of public health services?

STATES

Life Course Perspective:

Sees lives as a sequence of socially defined roles and events that are enacted over time by the individual

First step in Case Control Studies-

Selection of Cases- Formulating a disease or case definition. A case definition is usually based on a combination of signs, symptoms, physical & pathological examinations, and diagnostic test results. Once investigators have created a case definition, then they can begin case identification and enrollment.

Deontological Ethical Framework:

Set of clear rules which indicates that a given behavior is always right or always wrong Ex: Killing someone is ALWAYS wrong.

Sufficient Cause (Rothman's Causal Pies)

Set of conditions without any one of which the disease would not have occurred (this is one whole pie)

What is culture?

Sets of beliefs,behavior, norms, and practices. *learned *shared *dynamic

Which sampling method is the most ideal to use?

Simple Random Sample- You list each member of the population and use random numbers to decide which objects are in the sample (every individual has an equal chance or known chance of being selected) Purpose: avoids bias

Strengths and Limitations to Ecological Studies:

Strengths -rapid studies -can use existing data (convenience) -inexpensive -possible to identify important associations for further study Limitations -do NOT have individual sara -may not be able to identify temporal sequence -Ecological Fallacy- we do not know if any of the individuals with the outcome actually have the exposure -requires the need for additional research

Observational Study

Studies causes, preventions, and treatments for diseases; investigator passively observes as nature takes its course

Experimental Study Design

Studies preventions and treatments for diseases; investigator actively manipulates which groups receive the agent under study

A cohort study differs from a case-control study in that:

Subjects are enrolled or categorized on the basis of their exposure status in a cohort study but NOT in a case-control study

Critical Period Model

Suggests that certain exposures, occurring at a critical developmental moment, can strongly, perhaps singularly, influence future health outcomes

Causality History- "Divine Retribution"

Supernatural punishment of a person, a group of people, or everyone by a deity in response to some action. Many cultures have a story about how deity exacted punishment on previous inhabitants of their land, causing their doom.

T/F: Association does not mean Causation.

TRUE

T/F: Incidence and prevalence are measures of frequencies.

TRUE

T/F: Temporality is the most important criteria. Exposure MUST precede the disease.

TRUE

True or False: Tracing is REQUIRED for a typical cohort, but not for a typical case control study.

TRUE

True/False: A confounding variable must be associated with the exposure of interest & the diverse under study among both exposed and unexposed individuals.

TRUE

True/False: In case-control studies, people are selected based on their disease status, NOT exposure status.

TRUE

Target Population:

Target population is that population to which we want to have our results apply

Which is the most important Hill criteria?

Temporality - exposure must come before the disease Temporality is a sine qua non for causality.

Population:

The ENTIRE collection of individuals or measurements about which information is desired *Pay CLOSE attention to the research question* Examples: Counties, all USF students, hospitals within a state, Floridians etc.

What is the hallmark sign that distinguishes an experimental study from observational:

The active manipulation of the agent by the investigator

Causality History- "Body Humors"

The belief that an excess or deficiency of any of the 4 distinct body fluids in a person—- known as humors or humours—— directly influences their temperament and health. The 4 humors of Hippocratic Medicine are: black bile, yellow bile, phlegm, and blood and each corresponds to one of the traditional 4 temperaments.

Accuracy:

The degree to which the measurement actually represents what it is INTENDED TO REPEAT. HOW CLOSE IS THE MEASUREMENT TO THE TRUTH? (How well it centers around the mean)

Ratio:

The division of one number by another number and they don't have to be related

Hill Criteria for Causality: Analogy

The existence of an analogy (for example, if a drug causes birth defects, then another drug could also have the same effect) could strengthen the belief that an association is causal.

Ecological Fallacy:

While there may be ASSOCIATIONS between 2 factors in an ecological study, it is not possible to KNOW if the individuals with the risk factor are the ones who experience the outcome.

Stratified Sample:

a sample drawn in such a way that known subgroups (or strata) within a population are represented in proportion to their numbers in the general population -chosen specifically to represent different characteristics within the population -can lead to a good random representative sample

Probability Sample

a sample in which every element in the population has a known statistical likelihood of being selected -RANDOM -SRS, Systematic, Cluster or Stratified

Crude Rates:

a summary measure calculated by dividing the total number of cases in the population by the total number of individuals in that population at a specified time period Basic rate of disease that does NOT take into account any other factors

Percent Frequency Distribution:

a tabular summary of a set of data showing the percent frequency for each class

Nominal data "NAME"

data of categories/ groups only. Data cannot be arranged in an ordering scheme. (Gender, Race, Religion, Color, etc) Known as categorical, most basic level, and qualitative Nominal values can be stored as a word or text or given a numerical code. Numbers do NOT imply order To summarize nominal data, we use percentages or frequencies. NO mean or average value can be calculated.

Case Fatality Rate (CFR)

number of deaths due to a disease that occur among persons who are afflicted with that disease for a defined period of time Prognostic Measure

Morbidity Rate

number of people affected (new or existing cases) in relation to the total population in a given time period

Years of Potential Life Lost (YPLL)

number of years lost when death occurs before one's life expectancy Calculates this by identifying the expected age of death for a population and then identifies deaths that occur prior to that age to determine the years of potential life lost. Endpoints do vary and deaths at a very young age have a greater impact. Measures the relative impact of premature death on society.

Data:

observations and measurements for variables obtained Can be- measurements, observations, or descriptions of things

Percent Frequency:

relative frequency multiplied by 100