Epidemiology Final Exam Study Guide

descriptive epidemiology - epidemiologic studies concerned with characterizing the amount and distribution of health and disease within a population WHO is getting sick? (ex sex, age, race/ethnicity) WHERE are they getting sick? (ex country, rural/urban, near factory) WHEN are they getting sick? (over a day, year, decade) descriptive study designs - cross-sectional, case reports, case series, ecologic analytic epidemiology - examines causal hypotheses regarding the association between exposures and health conditions WHAT is making them sick? (ex virus, pollution, radiation, stress) observational analytic study designs - ecologic, case-control, cohort experimental analytic study designs - clinical trials, community intervention case reports/case series - individual-level observations; describe a particular clinical phenomenon in a single patient (case report) or a group of patients with similar problems (case series); goal to provide a comprehensive and detailed description of case(s) under observation; observational study ecologic studies - looks at group level data or population level data; often country levelecological fallacy - assuming that individuals within those populations follow the same trend that is seen in population-level data cross-sectional studies - exposure and disease outcome are determined simultaneously in each subject/patient "Prevalence study" or "snapshot in time" serial cross-sectional studies - trends in disease prevalence over time; surveying different individuals in same general group case-control studies - start with cases (those with disease), and controls (those without disease), look backward for past exposures (through interviews, medical records, etc) Start with disease status, look backward for exposure Cannot calculate prevalence or risk Good for rare diseases uses Odds Ratio biases in case-control studies - Selection bias: sources of cases (from one place may not be able to generalize), using incidence (wait for diagnosis and may die before diagnosis) or prevalence cases (risk factors related to survival instead of development of disease), selection of controls (best friend control, patients in hospital too similar) Information bias: can't remember information, lead to misclassification of exposure (put in wrong exposure group) = will bias results towards null findingRecall bias: one group systematically has better recollection of exposures than other group (usually case group) group matching in case-control studies - proportion of controls with a certain characteristic is identical to the proportion of cases with the same characteristic individual matching in case-control studies - for every individual case, a control is selected that matches the case in terms of all desirable variables (sex, age, etc.) = matched pairs Odds Ratio - Measure of association between frequency of exposure and frequency of outcome (exposed cases/not exposed cases)/(exposed controls/not exposed controls) OR 1 - positive association between exposure and disease OR = 2 - odds of disease are about 2x higher among exposed than among non exposed OR 1 - exposure may be protective factor OR = 1 - no association between exposure and outcome cohort studies - start with exposure status (exposed vs not exposed) and look for disease outcome (disease develops vs disease does not develop) Start with exposure, look forward to disease outcome Determines incidence/risk