Table 1.
The advantages and disadvantages of different observational study types
| Study type | Potential goals | Advantages | Disadvantages |
|---|---|---|---|
| Cross-sectional | - Population prevalence of exposure and/or outcome | - Relatively simple | - Poor for rarer exposures and outcomes |
| - Associations between exposures and outcomes | - Relatively cheap | - No causality may be inferred as exposures and outcomes are measured contemporaneously | |
| - Relatively quick | - Highly susceptible to information bias | ||
| - Good for common conditions and exposures | |||
| - May assess multiple exposures and outcomes | |||
| - Good for initial assessment of an exposure or outcome | |||
| Case–control | - Associations between exposures and outcome | - Relatively cheap | - Choice of controls notoriously difficult |
| - Strength of association in the form of odds ratio between exposure(s) in controls and exposure(s) in cases | - Relatively quick | - May only examine one outcome | |
| - May assess long latent periods | - Odds ratio not an intuitive measure | ||
| - Good for rarer outcomes | - Highly susceptible to selection and information bias and population stratification | ||
| Cohort | - Incidence rates | - Good for rare exposures | - Not simple |
| - Temporal associations between exposures and outcomes | - May examine multiple exposures and outcomes | - Not cheap | |
| - May assess long latent periods | - Not quick (unless retrospective) | ||
| - May assess temporal relationship between exposure and outcome inferring causality | - Highly susceptible to retention bias | ||
| - Susceptible to sampling bias |