S2) Epidemiological Study Designs Flashcards
Identify the epidemiological studies which are analytical
- Cohort studies
- Case-Control studies
Outline the methodology of a case-control study
- Find cases
- Find controls
- Compare & contrast for potential causal factors (exposures)
- Always retrospective
Outline the methodology of a cohort study
- Find exposed
- Find unexposed
- Compare and contrast for potential outcomes
- Can be retrospective/prospective
Identify the epidemiological studies which are observational
Cross-sectional surveys
Outline the methodology of a cross-sectional survey
Find cases
Define risk
Risk is the proportion dead at the end of a time period
Define rate
Rate is the incidence of death during a time period
Define prevalence
- Prevalence is the proportion of cases in the population at a given time
- It indicates how widespread the disease is
Define incidence
- Incidence is the rate of occurrence of new cases
- It conveys information about the risk of contracting the disease
What is risk ratio?
Risk ratio is the ratio of prevalence proportions of outcome in groups defined by levels of exposure at a particular time
What is rate ratio?
Rate ratio is the ratio of incidence rates of outcome in groups defined by levels of exposure after a particular time period
What is odds ratio?
Odds ratio is ratio of odds of outcome in groups defined by levels of exposure at a particular time
How do we interpret the odds ratio
- Ratio < 1: risk of the group of interest is less than the risk of the comparison group
- Ratio of 1: risk of the group of interest is the same as the risk of the comparison group
- Ratio > 1: risk of the group of interest is greater than the risk of the comparison group
What is Multivariate Analysis?
Multivariate analysis is a statistical technique for adjusting for multiple confounding factors simultaneously
How can prevalence be calculated?
Prevalence = Incidence x Duration of Disease
Which factors affect the duration of disease?
- Mortality
- Cure
