midterm 360

Endemic

(adj.) native or confined to a particular region or people; characteristic of or prevalent in a field

Framingham

(ongoing since 1948) investigates coronary heart disease risk factors.Smoking and lung cancer; e.g., Doll and Peto's study of British doctors' smokingAIDS, chemical spills, breast cancer screening, second-hand cigarette smokeAssociation between HPV and cervical cancer

Modern Concepts of Causality: Sir Austin Bradford Hill

1. Biological gradient (Dose-response relationship): An increased exposure to the risk factor causes a concomitant increase in disease (risk for heart disease is higher in heavy smokers compared to light smokers) 2. Biological plausibility: The data must make biological sense and represent a coherent explanation for the relationship. It must be credible on the basis of existing biomedical knowledge—but what if the biologic knowledge of the day is wrong, not up-to-date, etc.? 3. Experimental evidence: experimental designs provide the strongest epidemiologic evidence for causal associations, but they are not feasible or ethical to conduct for many risk factors—disease association. However, "natural experiments" that happen (remember Snow) may shed light on the subject! Think about the observation that dental caries decreased in populations with fluoride added to the water supply! 4. Analogy: Thalidomide and Rubella in pregnancy—caused great problems with the baby during pregnancy (birth defects [both], stillbirths, miscarriages), so considering this, "we would surely be ready to accept slighter but similar evidence with another drug or viral infection during pregnancy." Absolute causality is rarely established.... Some non-smokers get heart disease but most all smokers have heart disease....Smoking doesn't give you heart disease but puts you at greater risk for it. ***Keep in mind that there are multiple causes of disease in most cases—this is referred to as multiple causality.

Modern Concepts of Causality: 1964 Surgeon General's Report

1. Strength of association: Rates of morbidity and mortality must be higher for the exposed group than for the non-exposed group (risk of heart disease is higher in smokers than in non-smokers) 2. Time Sequence: Demonstration of correct temporal sequence: Exposure to the causal factor must occur before the effect, or the disease. 3. Consistency with other studies: Varying types of studies in other populations must observe similar associations. 4. Specificity of the association: The exposure variable must be necessary and sufficient to cause disease; there is only one causal factor. **This one is not as important today since diseases have multifactorial origins. 5. Coherence of explanation: the association must not seriously conflict with what is already known about the natural history and biology of the disease.

Bias

A particular preference or point of view that is personal, rather than scientific.

Cohort

A population group unified by a specific common characteristic, such as age, and subsequently treated as a statistical unit.

John Graunt

1662, published Natural and Political Observations Made upon the Bills of Mortality.Recorded seasonal variations in birthsand deathsShowed excess male over female differences in mortalityKnown as the "Columbus" of biostatisticsSee Yearly MortalityBill for 1632: The 10 Leading Causes of Mortality in Graunt's Time. He was the first to use quantitative methods to describe population vital statistics by organizing mortality data in a mortality table.His procedures allowed the discovery of trends in births and deaths due to specific causes

Alexander Fleming

1928—developed penicillin; it became available toward the end of WWII.

Wade Frost

1930's—advocated the use of quantitative methods to define public health problems.

Alexander Langmuir

1949—established the epidemiology section (EIS) of the CDC

Formative

: Will all plans and procedures work as conceived?

Outbreak

A localized disease epidemic, e.g., in a town or health care facility

Cause-Specific Rate

A measure that refers to mortality (or frequency of a given disease) divided by the population size at the midpoint of a time period times a multiplier.

Increases in lung cancer mortality, especially among women, illustrate which of the following trends in disease occurrence?

A new epidemic disorder

Clinical Trials definition

A research activity that involves the administration of a test regimen to humans to evaluate its efficacy and safety

Protocol

A study plan on which all clinical trials are based, Informed consent - The process of learning the key facts about a clinical trial before deciding whether or not to participate,

Infectious disease

A synonym for a communicable disease

Case-control

A type of retrospective study in which researchers begin with a group of people who already have the disease; studies that compare two groups: those who have a specific condition and those who do not have the condition.

Epidemic

A widespread outbreak of an infectious disease.

True or False? E. coli O157:H7 is not considered a threat to the food supply of the United States.

False, it is considered a threat

True or False? In current thinking, the term epidemic is used only to describe outbreaks of infectious disease.

False, it is used to dscribe a widespread outbreak of an infectious disease.

John Snow is credited with developing the smallpox vaccination.

False. Edward Jenner developed it

A vs P

Active Necessitates behavior change on the part of the subject Examples: Vaccinations and wearing protective devices Passive Does not require any behavior change Examples: Fluoridation of public water and vitamin fortifications of milk and bread products

Cross-sectional

Also termed prevalence study

Communicable

An illness caused by an infectious agent that can be transmitted from one person to another.

Intervention Studies

An investigation involving intentional change in some aspect of the status of subjects

Surveillance

Analysis and interpretation of these data.Dissemination of disease-related informationCommon activities include monitoring food born disease outbreaks and tracking influenza.

True or False? One of William Farr's contributions to public health and epidemiology included the development of a more sophisticated system for codifying medical conditions.

True

Arm

Any of the treatment groups in a randomized trial,

True or False? One of three main purposes of descriptive epidemiology is to aid in the creation of hypotheses.

True

Established in 1984 by CDC

BRFSS collects data from all 50 states plus DC, Puerto Rico, U.S. Virgin Islands, and Guam.

Phases of Clinical Trials

Before a vaccine, drug, or treatment can be licensed for general use, it must go through several stages of development.

Ethical Aspects of Human Experimentation

Benefits must outweigh risks.

Which of the following are examples of determinants of health?

Biological (bacteria and viruses), Chemical agents (carcinogens)., Stress, drinking, sedentary lifestyle, or high-fat diet

Birth Statistics: Certificates of Birth and of Fetal Death

Birth certificate includes information that may affect the neonate, such as congenital malformations, birth weight, and length of gestation.

How would one calculate Years of Potential Life Lost (YPLL)?

By subtracting the person's life span from the average life expectancy of the population

True or False? Randomized controlled trials at the community level are typically used in special situations where there is a simple intervention

True

Characteristics of Clinical Trials

Carefully designed and rigidly enforced protocol

What type of study begins with the "effect" (disease) and works backward towards the "cause"?

Case-control

Examples of Counts

Cases of influenza reported in Westchester County, New York, during January of a particular year. Traffic fatalities in Manhattan in a 24-hour time period College dorm students who had mono Foreign-born stomach cancer patients It sounds like counts are not that important, but just a single case report may be significant, depending upon what the infectious agent is. For example, if a single case of smallpox or Ebola was reported, the size of the denominator (or the size of the population—which is normally represented by the denominator) would not matter. **Counts are limited by themselves, though. Without involving other measures, they are just the number of cases.

Cyclic variations in the occurrence of disease may reflect

Changes in exposure to infectious agents Changes in the risk-taking behavior of persons Changes in temporary stressors Endogenous biologic factors

To test the efficacy of vitamin C in preventing colds, army recruits are randomly assigned to one of two groups: one in which 500 mg of vitamin C is administered daily, and one in which 500 mg of a placebo is administered daily. Both groups are followed to determine the number and severity of subsequent colds.

Clinical trial

To test the efficacy of a health education program in reducing the risk of foodborne and waterborne diseases, the residents of two Peruvian villages were given an intensive health education program. At the end of two years, the incidence rates of important water-borne and food-borne diseases in these villages were compared with those in two similar control villages without any education program.

Community trial

Primordial Prevention

Concerned with minimizing health hazards in general Inhibits the emergence & establishment of processes & factors, which are known to increase risk of disease: Economic conditions Social conditions Behavioral conditions Cultural patterns of living

Secular trends

Cyclical patterns Event-related clusters

Jenner Experiment

Dairymaids with Cowpox (vaccination—vaca=cow) were immune to smallpox. He used scabs from cowpox lesions onthe arm of a dairymaid to create the vaccine, then vaccinated an 8 year old boy with it. It worked! He then vaccinated his own children.Smallpox was eradicated worldwide, thanks to the smallpox vaccine, in 1978.

Mortality

Death rate

Limitations of Other Study Designs

Demonstrating temporality is a difficulty of most observational studies.

Population Dynamics

Denotes changes in the demographic structure of populations associated with such factors as births and deaths and immigration and emigration Two types of populations Fixed populations Dynamic populations

Outcome:

Did the program accomplish its ultimate goal?

High rates of mortality from hypertension found among African Americans may be due to

Dietary factors Exposure to stress Lack of social support Obesity

Four Trends

Disappearing: Conditions that were once common but are no longer present in epidemic form. Examples include smallpox, poliomyelitis, and measles. Brought under control by immunizations, improvement in sanitary conditions, and the use of antibiotics and other medications; led to eradication of smallpox and the elimination of the other 2 diseases in certain areas of the world. Residual: Contributing factors are largely known, but methods of control have not been implemented effectively Examples: STDs Perinatal and infant mortality among low SES persons Problems associated with alcohol and tobacco use Persisting: No effective method of prevention or cure has been discovered so they remain common. Examples: certain types of cancer and mental disorders New epidemic: diseases that are increasing markedly in frequency in comparison with previous time periods. Examples: Lung cancer, AIDS, Obesity, Type 2 diabetes The emergence of new epidemics of diseases may be a result of increased life expectancy of the population, new environmental exposures, or changes in lifestyle, diet, and other practices.

Snow

Discovered cause of cholera

Fleming

Discovered penicillin

Jenner

Discovered smallpox vaccine

Pandemic

Disease that occurs over a wide geographic area and affects a very high proportion of the population.

Criteria of causality:

Do they meet the criteria of causality we talked about? How large the effect? How consistent with previous research is it? Biologic plausibility?

Examples of trends

Dramatic changes have occurred: Chronic conditions have replaced acute infectious diseases as the major causes of morbidity & mortality The next slide will compare mortality causes in 1900 with those in 2009—leading causes of deaths in the U.S. in 2009 were heart disease, cancer, and chronic lower respiratory disease Recently, death rates for Alzheimer's disease, kidney disease, and hypertension have increased while death rates for heart disease, cancer, and stroke have been declining since the 1960's.

examples of recent epidemics

E coli, H1N1

According to the results of an ecologic study, the mortality rates for emphysema were found to be lower in central Los Angeles, California (a highly industrialized area), than they were in the desert resort of Palm Springs, California (a less industrialized area). This study appears to have determined that areas of high industrialization have lower rates of emphysema while areas of low industrialization have higher rates! After taking into account individual histories, it was discovered that many who lived in Palm Springs were retirees who had spent their entire lives in Los Angeles (or some other industrialized area of the U.S.). This is an example of __________________________

Ecologic fallacy occurs when incorrect inferences about the individual are made from group level data.

Eradicated

Erased; destroyed

When conducting a case-control study, the "controls" should be as similar to the cases in

Everything, except for the exposure of interest--only the cases should have been exposed., Everything, except for the existence of disease--only the cases should have the disease.

If a study involves both manipulation and randomization, it is a(n):

Experimental

Which type of Cohort study focuses on subjects with a common exposure

Exposure-based Cohort

True or False? A cross-sectional study allows the demonstration of a time sequence between exposure and disease.

False

True or False? In the United States, breast cancer is the leading cause of cancer deaths among females.

False

True or False? Intervention designs involve only controlled clinical trials.

False

Incidence

Fraction of a population that contracts a disease during a specific time

Snow's Contributions Linked the cholera epidemic to contaminated water supplies

Groundbreaking because he used many features of epidemiologic inquiry:He used powers of observationHe used a spot map (Cluster map) of cases He tabulated (counted) the number of fatal attacks and deaths

Which types of health issues are likely to be addressed in community trials?

HIV Smoking cessation Healthy eating

Impact:

Has the program produced any changes among the target group?

The Environment

Hippocrates wrote On Airs, Waters, and Places in 400 BC.He suggested that disease might be associated with the physical environment.This represented a movement away from supernatural explanations of disease causation.

Women's Health Initiative

Hormone Replacement Therapy (HRT)

Which type of evaluation requires the collection of baseline information before the program starts?

Impact evaluation

History of Clinical Trials

In 1537, Ambroise Paré applied experimental treatment for battlefield wounds.

Developing countries

In 1950 and 1990, countries had a triangular population distribution, which is associated with high death rates from infections, high birth rates, and other conditions that take a heavy toll during childhood years—things associated with poverty and deprivation: such as poor nutrition, lack of potable water, lack of access to vaccines and antibiotics, and unavailability of sewage treatment. By 2030, improvements in health are likely to result in greater survival of younger persons, causing a projected change in the shape of the population distribution. Developed countries Manifest a rectangular population distribution—it was consistent for 1950 and 1990, and is projected for 2030 with a few exceptions. Infections take a smaller toll and thus cause a greater proportion of children to survive into old age Residents enjoy greater life expectancy The population of developed countries will grow increasingly older due to continuing advances in medical care

Koch

In the late 1800's, Robert Koch actually proved that a human disease was caused by a specific living organism—he was experimenting with Tuberculosis.His research made possible the greater refinement of the classification of disease by specific causal organisms—he basically demonstrated, for the first time, a strict relation between a micro-organism and a disease. This helped provide definite criterion for identifying a specific disease. Before this, they were grouped in such a manner that it had actually hampered their epidemiologic study. His Postulates are shown here.....so for a specific disease to be the cause of an observed infection/disease, these 4 things must be met!

Morbidity

Incidence of a specific notifiable disease

6 Areas of focus of the U.S. Department of Health and Human Services:

Infant Mortality Cancer screening and management Cardiovascular disease Diabetes HIV/AIDS Immunizations

Process:

Is the program serving the target group as planned? Is number being served more or less than expected

Examples of Questions Investigated by Ecologic Studies

Is the ranking of cities by air pollution levels associated with the ranking of cities by mortality from cardiovascular disease, adjusting for differences in average age, percent of the population below poverty level, and occupational structure?

Case-control studies are among the best observational designs to study diseases of

Low prevalence

Phase III trials: protective efficacy

Measurement of vaccine coverage Serologic surveillance Safety and efficacy of vaccine Post-licensing evaluation

Ignaz Semmelweis

Mid-19th century, Viennese hospital Clinical assistant in obstetrics and gynecology Observed higher mortality rate among the women on the teaching wards for medical students and physicians than on the teaching wards for midwivesPostulated that medical students and physicians had contaminated their hands during autopsiesIntroduced the practice of hand washing

Secondary Prevention

Occurs during pathogenesis phase Designed to reduce the progress of disease Examples include: screening programs for cancer and diabetes. Breast exams, mammograms, PSAs, testicular exams.

Efficacy

None of the above

Toxicity

None of the above,

Crude death rate

Number of deaths in a given year Reference population (during the midpoint of the year) x 100,000

Crude Birth Rate =

Number of live births / total population per 1000

Incidence rate =

Number of new cases over a time period/ Total population at risk during the same time period) X multiplier (e.g., 100,000)

Attack Rate

Number of people exposed to a specific agent who develop the disease ÷ total number of people exposed an incidence rate calculated for a particular poplation for a singe disease outbreak and expressed as a percentage

Interpretation of an Odds Ratio (OR)

OR = 1 implies no association.

True or False? The 2009-2010 episode of influenza first identified in the United States and eventually called 2009 H1N1 influenza was classified as a pandemic by WHO in summer 2009.

True

Pare

Pare—turpentine, rose oil, egg yolks concoction to treat battlefield wounds—was better than boiling oil at treating wounds!

Cohort Strength

Permit direct determination of risk.

Wade Hampton Frost

Popularized cohort analysis method.

Three types:

Positive declaration (research hypothesis) Negative declaration (null hypothesis) Implicit question (e.g., to study association between infant mortality and region)

Stages in the Development of A Vaccination Program

Pre-licensing evaluation of vaccine

True or False? The HHANES was a major study of health of Latinos in the United States.

True

You are interested in finding out whether middle-aged men who have premature ventricular contractions (PVCs) are at greater risk of developing a myocardial infarction (heart attack) than men whose heartbeats are regular. Electrocardiogram (ECG) examinations are performed on all male office employees 35 years of age or older who work for oil companies in Houston. The ECG tracings are classified as irregular or regular. Five years later, myocardial infarction rates are compared between those with and those without baseline ECG irregularities.

Prospective cohort study

Interpretation of Prevalence

Provides an indication of the extent of a health problem. Example 1: Prevalence of diarrhea in a children's camp on July 13 was 15. Example 2: prevalence of obesity among women aged 55-69 years was 367 per 1,000.

HES

Provides direct information about morbidity through examinations, measurements, and clinical tests

True or False? The Women's Health Initiative demonstrated that the benefits of hormone replacement therapy for cardiovascular disease had been overestimated.

True

True or False? The three categories of descriptive epidemiologic variables are person, place, and time.

True

CHIS

Provides information on the health and demographic characteristics of California residents

Gini Index: a common measure of income inequality

Range: 0 - 1 The closer it gets to 1, the greater level of inequality. In 2007, the U.S. was 0.46 Association between the Gini index and health inequality is reported using the number of healthy days for a state. The higher that number, the lower the health inequality. The 3 states with the lowest health inequality: Utah, Connecticut, North Dakota The 3 states with the highest health inequality: Tennessee, Kentucky, and West Virginia

The HIPAA Privacy Rule

Refers to the Health Insurance Portability and Accountability Act of 1996

which disease has been eradicated

Small pox

Random assignments

Researchers' assignment of of participants to groups by chance, to reduce the likelihood that an experiment's results will be due to preexisting differences between groups

As an epidemiologist you are going to investigate the effect of a drug suspected of causing malformations in newborn infants when the drug in question is taken by pregnant women during the course of their pregnancies. As your sample you will use the next 200 single births occurring in a given hospital. For each birth a medication history will be taken from the new mother and from her doctor; in addition, you will review medical records to verify use of the drug. [N.B.: These mothers are considered to have been followed prospectively during the entire course of their pregnancies, because a complete and accurate record of drug use was maintained during pregnancy.] The resultant data are: Forty mothers have taken the suspected drug during their pregnancies. Of these mothers, 35 have delivered malformed infants. In addition, 10 other infants are born with malfunctions. What type of study design is this?

Retrospective cohort study

Phase I trials:

Safety of adult volunteers

Demographic Transition

Shift from high birth and death rates found in agrarian societies to lower birth and death rates found in developed countries. Decline in death rate: attributed to improvement in general hygienic & social conditions Decline in birth rate: attributed to industrialization and urbanization Industrialization and urbanization, while they have led to a decline in the birth rate, both have led to environmental contamination, concentration of social and health problems in the urban core areas of the US, and out-migration of inner city residents to the suburbs. Remember in Chapter 1 when we talked about Population Density and the problems it caused?!

Adjusted Rates

Statistical procedures applied to make crude rates more comparable -total population but is statistically adjusted for a certain characteristic, such as age

Relevance to each patient:

Studies are done in GROUPS—be careful trying to apply conclusions from observations of groups to an individual (can't really tell an individual that he/she is 20 times more likely to get lung CA because he/she smokes—but you can say that GROUPS of individuals who smoke are 20 times more likely to get lung CA.)

Seven Uses for Epidemiology

Study history of the health of populations Diagnose the health of the community Examine the working of health services Disease Etiology: Estimate the individual risks and chances Identify syndromes Complete the clinical picture Search for causes

Which of the following activities characterizes an epidemiologic approach (as opposed to a clinical approach)?

Surveillance of a population

Tertiary Prevention

Takes place during late pathogenesis Designed to limit disability from disease Also directed at restoring optimal functioning (rehabilitation) Examples include: physical therapy for stroke patients, halfway houses for alcohol abuse recovery, and fitness programs for heart attack patients.

Advantages of Case-Control Studies

Tend to use smaller sample sizes than surveys or prospective studies

True or False? Treatment crossover refers to any change of treatment for a patient in a clinical trial that involves a switch of study treatments.

True

True or False? WHO is a major source of information about worldwide international variations in rates of disease.

True

Which of the following is the best definition of mortality?

The deaths that occur in a group

Applications of Ecologic Approach

The effect of fluoridation of the water supply on hip fractures

In case-control studies, the odds ratio is used as an estimate of the relative risk. In order for this approximation to be reasonable, some conditions must be met. Which of the following conditions is not necessary in order to use the odds ratio to estimate the relative risk?

The exposure in question is rare in the population

Descriptive vs. Analytic Epidemiology

The first one describes the distribution of disease (person, place and time) and its hypothesis is often general and implicit, although it can also be explicit and more specific. The second one tests a hypothesis about an association between an exposure and a disease. Motivation is often to ultimately identify a causal determinant. Hypothesis usually specific.

Ecologic

The gradual and orderly process of change in an ecosystem brought about by the progressive replacement of one community by another until a stable climax is established

Selection of Controls

The ideal controls should have the same characteristics as the cases (except for the exposure of interest).

Which of the following statements most accurately expresses the downward-drift hypothesis for schizophrenia?

The illness leads to the clustering of psychosis in the impoverished areas of a city.

Mill's Canons of Inductive Reasoning

The method of difference--all the factors in two or more places are the same except for a single factor. The method of agreement--a single factor is common to a variety of settings. Example: air pollution. The method of agreement--a single factor is common to a variety of settings. Example: air pollution. The method of residues--involves subtracting potential causal factors to determine which factor(s) has the greatest impact.

Epidemic threshold

The minimum number of cases (or deaths) that would support the conclusion than an epidemic was underway.This is based on statistical projections.

Neonatal Mortality Rate

The number of deaths of infants less than age 28 days per 1000 live births per year.

Prevalence

The number of existing cases of a disease or health condition in a population at some designated time

Phase IV

There can be more than three phases in a clinical trial. Unplanned crossovers exist for various reasons, such as patient's request to change treatment. In planned crossovers, a protocol is developed in advance; the patient may serve as his or her own control. involve post-marketing research to gather more information about risks and benefits of a drug.

Prevalence

The number or proportion of cases of a particular disease or condition present in a population at a given time.

Blinding

The practice of concealing group assignment from study subjects, investigators, and/or those who assess subject outcomes, typically in the context of a randomized controlled trial. For ex, study subjects may receive capsules with identical appearance and taste; however, the treatment group receives the active drug, whereas the control group receives the placebo.

Health Status and Health Services

The rise and fall of diseases and changes in their characters: Illnesses and causes of morbidity have changed over time. Chronic conditions have generally replaced acute infectious disease as a major cause of morbidity and mortality. Describe the health of the community: can provide a key to the types of problems that require attention and also accentuate the need for specific health services—this is helpful to public health practitioners and administrators as it helps them plan for allocation of resources. Epidemiology and policy evaluation: Epidemiologic research helps lawmakers develop evidence-based laws to safeguard the public. Examine the working of health services: to help improve them! Operations research: assessing what is available, what the community expects and what it needs. Program evaluation: the success of services delivered and the effects on community health have to be appraised

Surveillance

The systematic collection of data pertaining to the occurrence of specific diseases.

Infant Mortality Rate

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

Crude Birth Rate

The total number of live births in a year for every 1,000 people alive in the society.

Ratio

The value obtained by dividing one quantity by another. Consists of a numerator and a denominator. The most general form has no specified relationship between numerator and denominator. Rates, proportions, and percentages are also ratios.

quantification

This method translates qualitative data into numbers! Qualitative data is descriptions/words about observations that a physician or researcher has made about the types of people (age, sex, race) among whom a disease seems to be common as well as exposure category & clinical features. Epidemiologists may use graphs or charts to demonstrate the quantification. So the number of cases are counted and disease distributions are examined according to demographic variables such as age, sex, race, and other variables, such as exposure category and clinical features.

Three Broad Objectives of Descriptive Epidemiology

To evaluate and compare trends in health and disease To provide a basis for planning, provision, and evaluation of health services To identify problems for analytic studies (creation of hypotheses)

According to your book, an example of a non-infectious epidemic is the red spots that appeared on the airline flight attendants.

True

As the size of the Cohort study increases, so does the cost.

True

Cohort studies generally enforce the fact that the timing of cause (exposure) happens before effect (disease).

True

The 1918 Influenza Pandemic is also known as "the Mother of All Pandemics."

True

True or False? A case-control study is purely a descriptive (as opposed to analytic) study design

True

True or False? Clinical trials enroll individual subjects and enable randomization of subjects to receive or not receive the intervention.

True

True or False? Controls are needed in a case-control study to evaluate whether the frequency of a factor or past exposure among the cases is different from that among comparable persons who do not have the disease under investigation.

True

True or False? Exposure-based cohort studies permit investigations of exposures that are uncommon.

True

True or False? In community intervention studies, it is important for the investigator to evaluate whether a program has achieved its intended results before assuming the benefits of the intervention.

True

True or False? Lung cancer is the leading cause of cancer deaths among both males and females in the United States.

True

True or False? Nativity refers to place of origin of an individual.

True

Limitations of Case-Control Studies

Unclear temporal relationships between exposures and diseases

Incidence Rate

What is the term for the number of new events occurring in a population divided by the population at risk?

Factors Affecting Reliability of Observed Changes

When we are looking for the reasons for these trends, we have to take into account certain conditions that may affect the reliability of the observed changes. These things can be variations in diagnosis, reporting, case fatality, or something else.....let's look at these in a bit more detail: Lack of comparability over time due to altered diagnostic criteria: the diagnostic criteria used in a later time reflect new knowledge about a disease and therefore may be more precise (considerable information has been obtained over ¾ of a century about chronic diseases!); some categories of disease may be omitted altogether. Aging of the general population: due to reduced impact of infectious diseases, better medical care, and a decline in the death rate; also the cause of death may be wrongly attributed to a disease in elderly with multiple co-morbidities—multiple organ systems may fail simultaneously. Changes in the fatal course of the condition: may be seen over the long run of a disease—decreases in the number of people who actually die of it.

Examples of Case-Control Studies

Young women's cancers resulting from utero exposure to diethylstilbestrol

The CONSORT Statement is

a protocol that guides the reporting of randomized trials by providing a 22-item checklist and a flowchart.

Public health implications:

a risk factor that may not be important for an individual may be important when multiplied over the population as a whole!

Proportion

a(a+b) x 100

"epidemic threshold" is a certain percentage

above what is considered normal for that period. The normal level, or baseline, is statistically determined based on data from past flu seasons.

General Fertility Rate

annual number of live births per 1000 women of childbearing age

Epidemiologic methods

are used to describe the Health of the Community. Epidemiologic methods and studies also provide a key to the types of problems that require attention and also determine the need for specific health services

Case control studies:

the study begins after the health outcome has already occurred. People are selected from a population because they are known to have the outcome of interest (cases) or they are known NOT to have the outcome of interest (controls). Do the people with the outcome of interest (cases) have the exposure characteristic (or history of exposure) more frequently that those without the outcome (controls)?

Hypotheses

theories tested by gathering facts that lead to their acceptance or rejectio

Marital status is an important descriptive epidemiologic variable because it is

theorized to be a selective factor in health theorized to be a protective factor in health

Cross-sectional

type of study that measures a variable across several age groups at the same time

A major advantage of cohort studies over case-control studies with respect to the role of a suspected factor in the etiology of a disease is that:

use subjects drawn from a cohort study provide a degree of control over confounding reduce the cost of collecting exposure information

Prepathogenesis

before agent reacts with host

Descriptive studies

used to identify a health problem that may exist.

Number of controls

usually it is a one-to-one ratio—one control for each case, but researchers can also accept up to a 4:1 controls to cases ratio. This is the maximum

Subjects for an exposure-based cohort study would be selected most appropriately from:

certain occupational groups such as battery workers the residents of a large U.S. county male Harvard alumni from 1916 to 1950

An example of passive follow-up in cohort studies is:

collection and maintenance of data by the federal government

Eliminated

completely removed in an area, some cases may appear elsewhere

Joseph Goldberger

cure for pellagra—a nutritional deficiency disease characterized by the 3 D's: dermatitis, diarrhea, and dementia.

Reasons for gender differences in mortality may include

greater frequency of smoking among men

Experimental studies

help us to overcome some deficiencies in observational studies! By exercising control over who will receive the exposure as well as the level of exposure, the investigator in an experimental study more confidently may attribute cause and effect to associations than in observational designs

AR =

ill/ ill + Well x 100 (during a time period)

Phase II trials

immunogenicity and reactogenicity in the target population.

Surveillance is performed

data is collected pertaining to the occurrence of the specific disease or outbreak; then data is compared to the usual occurrence of the disease to see if there is an increase

Community trials

determine the potential benefit of new policies and programs, refers to defined unit (state, county, school district), start by determining eligible communities and their willingness to participate, collect baseline measures of the problem to be addressed, use variety of measures (disease rate, knowledge, attitude and practices), communities randomized (receive intervention not receive the intervention) and followed over time, outcomes of interest are measured

pathogenesis

development of disease

Large international variations in rates of infectious and communicable diseases as well as other conditions are most likely explained by:

differences in climate differences in cultural factors national dietary habits access to health care

epidemiology

distribution and determinants of health and diseases, morbidity, and mortality in populations doesn't mean a large number, one or two cases. When a disease has disappeared and a single case reappears, that is an epidemic. Greek- upon people

Clinical trials

experiments that study the effectiveness of medical treatments on actual patients a research activity that involves the administration of a test regimen to humans to evaluate its efficacy and safety, the outcomes in the treated group are compared with outcomes in an equivalent control group

Analytic studies

follow descriptive studies, and are used to identify the cause of the health problem

Proportional Mortality Ratio (PMR) %

the proportion of all deaths in a population which is due to a particular cause: usually expressed as a percentage

Cause-specific Rate

looks at only the number of deaths from a particular disease or condition within a year divided by the average midyear population

@ birth

m/f x 1000

Sex ratio

male/female

demo sex ratio

male/female x 100

Natural experiments

naturally occurring circumstances in which people in a population have different levels of exposure to a supposed causal factor in a situation resembling an actual experiment, a situation in which human subjects are randomly allocated to groups In most experiments, the presence of a person in a particular group is typically nonrandom!

Double blinding

occurs when neither the subject nor investigator is aware of which treatment group the subject has been randomized to.

The difference between primary and secondary prevention of disease is:

primary prevention means control of causal factors, while secondary prevention means early detection and treatment of disease.

Social Security

provides data on disability benefits and Medicare.

Health insurance

provides data on those who receive care through a prepaid medical program.

Life insurance

provides information on causes of mortality; also provides results of physical examinations.

The purpose of randomization is to

reduce error that results from assignment to study conditions

The purpose of double-blinding in clinical trials is to:.

reduce error that results from the way in which the outcome is assessed reduce error that results from subjects' knowledge of their assignment to study conditions

This lengthy process requires balance to:

satisfy the urgent needs for new vaccines protect the public from a potentially deleterious vaccine

The uses of epidemiology include

search for determinants (causes of disease) estimation of individual risks and chances of contracting disease evaluation of health services

Studies of nativity and migration have reported that

some migrants have inadequate immunization status with respect to vaccine-preventable diseases

The methods used in determining whether or not an epidemic is occurring are

surveillance and epidemic threshold.

The history of epidemiology began with

the Greeks and Romans!Environment and diseaseThe Black DeathUse of mortality countsSmallpox vaccinationUse of natural experimentsWilliam FarrIdentification of specific agents of diseaseThe 1918 influenza pandemic

Proportional Mortality Ratio

the equal loss of subjects from both the program and nonprogram groups

Total Fertility Rate

the number of children an average woman will bear during her lifetime; this information is based on an analysis of data from preceding years in the population in question.

John Snow, author of Snow on Cholera

was an early epidemiologist who used natural experiments.

Lung cancer mortality among women is increasing faster than among men. What factor(s) would most likely account for this increased cancer rate?

women are smoking more