Epidemiology 4 Flashcards
What is a risk factor?
An environmental, behaviorural or biological factor confirmed by temporal sequence, usually increasing the probability of a disease occurring and if absent or removed, reduces the probability. Risk factors are part of the casual chain, or expose the host to the casual chain. Once disease occurs, removal of a risk factor may not result in a cure.
What is the Bradford Hill criteria?
Strength of association Dose response Change in risk factor-reduction Time sequence Consistency Specificity- defined exposure Biological plausibility Experimental preventative trials.
What is a cause?
An external agent which results in disease in susceptible individuals.
What is a confounding variable?
A confounding variable, also called a confounder or confounding factor, is a third variable in a study examining a potential cause-and-effect relationship.
A confounding variable is related to both the supposed cause and the supposed effect of the study. It can be difficult to separate the true effect of the independent variable from the effect of the confounding variable.
In your research design, it’s important to identify potential confounding variables and plan how you will reduce their impact
FOR EXAMPLE:
Drug trial for control of hypertension
Test group- drug, placebo (control)
Result: test group lower blood pressure than placebo group
Confounding variable: average age of test group significantly lower than control group. Hypertension age related, therefore may be due to age difference rather than effect of a drug.
What is a risk factor hypothesis?
Suggestion that exposure to a particular agent may cause the development of a particular disease if susceptible individual exposed to an agent in question
OR
Suggestion that possesion of certain characteristics may make disease outcome more likely if exposed to certain agents.
What is examples of examination of descriptive data?
Decrease in caries levels associated with war-time sweet rationing
Higher incidence of oral cancer in west of Scotland compared with the rest of the UK.
What are three common indices of risk?
Absolute
Relative
Attributable.
What is absolute risk?
Most basic measure
Incidence rate of disease amongst people exposed to agent
Not very useful, as assumes no risk incurred by people not exposed to agent.
What is attributable risk?
Difference between incidence rates in exposed and non-exposed groups
Represents the risk attributable to factor being investigated.
What is relative risk?
Ratio of incidence rate in exposed group to incidence rate in non-exposed group
Measurement of proportionate increase in disease rates of exposed group
Makes allowance for frequency of disease amongst people not exposed to supposed harmful agent.
What is an analytic observational study?
Search for association between factor or set of factors and a disease
Observational- not experimental
Investigator observes what is happening normally in a population
Involves comparing disease experience of two or more groups of people in relation to their possession of certain characteristics or exposure to a suspected factor of factors
-designed to test hypothesis.
What are the two types of analytic observational studies?
Cohort
Case-control.
What is the study design of a cross-sectional study?
Descriptive.
What are cohort studies?
Prospective studies
Recruit group of people who have not manifest the disease at time of recruitment and assess risk factors
Individuals observed over period of time to measure frequency of occurrence of disease among (people exposed to risk factor and people not exposed to risk factor).
What are case control studies?
Retrospective studies
Compare individuals with disease with those without disease
Trace back to assess risk factors:
past histories and exposure to suspected harmful agents compared
-should be a random sample
-value of study profoundly affected by method of selection of cases and controls
-may be used for preliminary investigation of hypothesis
-less robust than cohort.
