2 Epidemiology: Concepts and Methods Free Online FlashCards

What does epidemiology study?

Epidemiology systematically studies the distribution and determinants of health-related conditions in populations and uses that knowledge to prevent and control health problems.

Which dimensions organize descriptive epidemiology?

Describe cases by person, place, and time. These patterns can reveal clues and generate hypotheses for analytic studies to test.

Why are case counts alone inadequate for comparing populations?

Relate case counts to an appropriate population denominator. Define the condition, population, and time period so comparisons reflect comparable groups.

How is incidence proportion calculated?

Incidence proportion, or risk, is the proportion of people initially free of the condition who develop it during a defined interval: $\frac{\text{new cases during the interval}}{\text{people at risk at the start}}$.

What denominator does an incidence rate use?

Incidence rate is new cases relative to the total person-time people were observed and at risk: $\frac{\text{new cases}}{\text{total person-time at risk}}$.

What does prevalence measure?

Prevalence is the proportion of a population with a condition, whether newly diagnosed or already present: $\frac{\text{existing cases}}{\text{population assessed}}$.

How do point and period prevalence differ?

Point prevalence is a snapshot at a specified time. Period prevalence includes people who had the condition at any time during a defined interval.

How does a cohort study compare exposure and outcome?

A cohort study groups people by exposure and follows them to compare new outcomes. It can measure incidence and establish whether exposure preceded outcome.

How are participants selected in a case–control study?

A case–control study starts with people who have the outcome and a comparison group without it, then compares their prior exposures. It is often efficient for rare outcomes.

What is a key limitation of cross-sectional studies?

A cross-sectional study measures exposure and health status at about the same time. It can estimate prevalence, but timing may be unclear, limiting cause-and-effect conclusions.

How does a randomized trial evaluate an intervention?

Investigators assign an intervention, often randomly, and compare group outcomes. Randomized trials can provide strong evidence about intervention effects when feasible and ethical.

What is confounding?

Confounding occurs when a third factor related to both exposure and outcome partly or wholly explains their association.