Epidemiology Final

Risk Ratio Rquation

(A/n1)/(C/n2)

What are the properties of a cofounder?

- Must be an independent cause or predictor of the outcome (associated with outcome) - Must NOT be an intermediate step on the causal pathway (can NOT be an effect of the exposure.) - Must be an independent cause or predictor of the outcome (associated with outcome)

what are the key factors of information bias?

- always happens after participants are enrolled - differences in the way that information is collection - most common type (placed in wrong group) - comes from self reports, medical record errors, data entry errors, non-specific disease/exposure definitions

4 Components of an Outbreak

1. clinical (symptoms, lab results) 2. person (who gets the disease) 3. place (where is the disease happening) 4. time (what time period)

Properties of a confounder

1. must be an independent cause or predictor of the outcome 2. must be associated with the exposure 3. must NOT be an intermediate on the casual pathway

what causes a virus to spillover from animals to humans?

1. person must be exposed to animals 2. virus must be capable of infection humans

A person was enrolled in a study on the association between alcohol use and death on 1/1/2019. They were followed until 1/1/2020, at which point they were lost to follow up. On 1/1/2021 they turned up alive and resumed participating in the study until the study concluded on 1/1/2022. How many years of Person Time did this person contribute to the study?

3

What slice of the pie is the Necessary Cause?

A - it is present in every causal pie

Dynamic Populations

A population whose membership is defined by being in a state or condition

Fixed populations

A population whose membership is defined on the basis of some EVENT

Cumulative incidence equation

A/N where A = # of people developing disease during a specified time period and N = # of people followed for the specified time period

Incidence Rate equation

A/PT where A = new cases during time period and PT = total person - time of observation in a population at risk

The epidemiological triangle consists of:

Agent, host, disease

What are common control measures used in a disease outbreak?

Behavioral interventions Vaccine campaigns Medication distribution Person protective equipment

If we don't know the cause or pathogen of a disease, we can

Design and conduct an epidemiological study

What are the five components of an outbreak investigation?

Determine the cause (hypothesis) Design a study Collect and record data Control measures Communication

True or False: Poor recall is a type of recall bias

False

A student was exposed to SARS-CoV-2 on September 12. Their symptoms began on September 18. What do you call the time period between exposure and onset of syptoms?

Incubation period

The process of gaining the agreement of all eligible and willing individuals to participate in an experimental trial is referred to as which of the following?

Informed consent

Non-differential misclassification

Misclassification on one measure (exposure OR outcome) is independent of the other Can bias results toward or away from the null

differential misclassification

Misclassification on one measure (exposure OR outcome) is related to the other

What type of misclassification is this: When misclassification on one measure (exposure OR outcome) is independent of the other

Non-differential

What is the primary weakness of case control studies?

Not good for rare exposures

What is the primary weakness of cohort studies?

Not good for rare outcomes

What is the primary weakness of cross sectional studies?

Not good for rare outcomes or exposures

Prevalence equation

P/N where P = cases and N = population

What are the types of epidemiological surveillance

Passive, active, sentinel, syndromic, other (social media)

During an outbreak investigation we use surveillance to help us determine what characteristics of a disease?

Person, place, time

What do you need to know to measure disease frequency?

Population, time, and cases of the disease

Benefits of case counts

Provide an estimate of the magnitude and relative magnitude of the problem They are easy(-ier) to understand Useful in advocacy/public policy Useful for planning health care delivery

What is the main measure of infectivity?

R0

Infectivity

R0 = the basic reproductive number, the number of cases of average an infected person will cause during their infectious period

risk difference equation

Risk Difference (RD) = Riskexposed - Riskunexposed RD = (A/n1)-(C/n2)

Measures of association

Risk difference Risk ratio Incidence rate difference Incidence rate ratio Odds ratio Attributable risk

Relative Risk (RR)

Riskexposed/ Riskunexposed

Risk difference

The difference in risk of disease between the exposed and unexposed groups

Incidence

The occurrence of new cases of a disease in a population during a specified time period Involves the transition from one state to another Denominator only includes the population AT RISK

Cumulative Incidence

The proportion of a population at risk that develops the disease over a specified time period

Incubation

Time interval between initial contact with an infectious agent and appearance of the first sign or symptom of the disease in question

A study where subjects at risk of the outcome are defined according to their exposure and followed over time to determine the incidence of the outcome is called...

a cohort study

what type of measure is a risk ratio?

a relative measure

Prospective Cohort Study

a source population is divided into exposed and unexposed groups at the beginning of a study by researchers and their disease status is observed

Association

a statistical relationship between two variables

epidemic

a sudden increase in the number of cases, above what is normally expected

Outbreak

a true increase of disease above baseline

Odds Ratio Equation

ad/bc

odd ratio equation

ad/bc

what type of measure is a risk difference?

an absolute measure

What is the primary strength of a case control study?

an be conducted after exposures and cases have started

pandemic

an epidemic that spreads over several countries

endemic

baseline amount of a disease to is usually present in a community

What are the types of control measures?

behavioral, vaccination, medication, environmental measures, infection control, health education

Response Bias

bias that occurs due to the differences in people who are willing to participate in studies and those who don't. maximize response rates to minimize effects all study designs

measures of frequency

case counts, prevalence, risk/cumulative incidence, and incidence rate

The outcome is known at the beginning of what kind of study?

case-control study

Clusters

cases that are grouped in a time or space bu may not represent a real increase over time

The "lifetime risk of breast cancer" among women is a commonly cited measure of which of the following? prevalence, incidence rate, cumulative incidence, case counts

cumulative incidence

Interviewer Bias

difference in the way the information is solicited, recorded, or interpreted type of information bias

Absolute measures of association are some sort of __________ , while relative measures of association are some kind of __________

difference, ratio

How can we slow dug resistance?

do not share antibiotics/drugs poor hygiene avoid close contact with people who are ill keep vaccination up to date

An investigator identifies a strong association between ice cream and shark attacks. This association is likely:

due to confounding

period prevalence

during a time period

What slices of the pie are considered Component Causes?

each slice is a component cause

What is the primary strength of a cross sectional study?

easy and inexpensive

What were the main findings of the Dutch famine of 1944-1945?

effects of undernutrition were dependent of the timing of the onset of the famine

Cross-Sectional Study

examines the relationship between disease and other factors in a defined population at a single point - snapshot in time - measures exposures prevalence in relation to disease prevalence

Prevalence

existing disease burden

What type of experiment is considered the gold standard in epidemiology?

experimental

True or False: confounders are only associated with the exposure

false

True or False: the speed of drug resistance is uncontrollable

false

True or False? When the direction of the bias is toward the null, it means that the error causes the true measure of association to be overestimated.

false

What type of population depends on the the occurrence of an event?

fixed population

Systematic Error

flaws in design/conduct of a study that lead to an erroneous association between exposure and disease (consistently wrong in a particular direction)

What is the primary strength of a cohort study?

good for rare exposures

Inappropriate Control Selection

happens when the control group is not selected from the same population as the diseased/exposed group only happens in case-control studies

Information Bias

happens when the information you collect from/about your participants is erroneous

The ______ period is the time between initial contact with an infectious agent and the appearance of symptoms; the ______ period is the time between exposure and the onset of the infectious period (when you can transmit the disease).

incubation, latency

Case-Control Study

individuals from a source population are selected and divided into cases of disease and controls which are then compared

Bias that can occur if the data you collect from (or about) your participants is erroneous is called

information bias

What type of bias occurs AFTER participants are enrolled in the study

information bias

Incubation Period

interval between initial infection and first signs and symptoms

Fixed Population

membership is based on a event, it is permanent

Dynamic Population

membership is based on a state/condition, transient membership

How can we expedite drug resistance?

misusing antibiotics poor infection prevention/control measures living and working in unclean conditions mishandling food

Confounding

mixing of effects between an exposure, an outcome, and a third extraneous variable

Which of the following is a general word that can apply to a disease, condition, or event? Morbidity, mortality, incidence, and prevalence

morbidity

point prevalence equation

number of people w/ a disease at a time/the total population at that time

period prevalence equation

number of persons who have the disease during a specified time period / number of persons in the population during that specified period

Cumulative incidence

occurrence of a new disease

Selection Bias

one relevant group in the population has a higher probability of being selected

who accrues person time?

people at risk and while being followed

Which of the following refers to the proportion of the population that is diseased during a specified duration of time, such as the year 2021? point prevalence, period prevalence, and incidence rate

period prevalence

Components of a Case Definition

person, place, time

When a spike in disease cases serves as the source for future disease spikes, we see what kind of an outbreak curve?

propagated outbreak curve

Random Error

proportion of variation in a measurement that has no apparent connection to a measurement or variable (by chance)

An investigator sought to study the association between air pollution and COVID-19 on UVM's campus. The investigator enrolls 100 freshmen, gives them each an air monitor to monitor their air pollution, and follows them until graduation to see if they develop COVID. What kind of study design is this?

prospective cohort study

Case counts

raw numbers of disease

Selecting a diseased control group is the most common method for minimizing which type of bias?

recall bias

Retrospective Cohort Study

records are obtained of diseased and undisposed individuals from a source population and their exposure status is observed through records (in the past)

Bias due to differences in those who do and who do not agree to participate in a study due to both exposure and disease is called

response bias

An investigator is interested in the association between Tylenol use and Myocardial Infarction (a heart attack). The investigator has access to the Nurses Health Study data and pulls data reported by 3,000 women in 1981 and assess their reported Tylenol use. Then, the investigator evaluates whether any of these women developed a Myocardial Infarction before 2015. What kind of study design is this?

retrospective cohort study

What can we estimate in cohort studies?

risk difference, risk ratio, incidence rate, and cumulative incidence

What type of bias can occur when one group in the study population has a higher probability of being included in the study sample?

selection bias

point prevalence

specific point in time

Incidence rate

speed of new cases of disease

Case Definition

standard criteria for classifying whether a person has a particular disease

Association

statistical relationship between two variables

Person time

the amount of time an individual (or the population) is followed

What parts of the pie make up Sufficient Cause?

the complete pie

Causation

the exposure produces the effect

Causation

the exposure produces the risk

Infectivity

the number of cases on average an infected person will cause during their infectious period

latency period

the period between exposure and the onset of the period of communicability

odds ratio

the ratio for the odds of an event occurring in an exposed group to the odds of that event happening in the unexposed group specific for case control studies

risk ratio

the ratio of the probabilities of an event in the exposed vs unexposed groups

Latency Period

the time from exposure to infectiousness

True or False: drug resistance is naturally occurring

true

What factors have increased the number of infectious diseases?

urbanization, poverty, and climate change

Recall Bias

when cases and controls systematically have different memories of the past type of information bias

when does person time stop accruing?

when the person is no longer a part of the population at risk, they develop the disease, they die, is lost to follow-up, no longer meets the eligibility, observation period ends