Which data sources are commonly used for cohort studies, and what is a typical strength?

• A. Questionnaires only; strength: rapid data collection
• B. Medical records, registries, and questionnaires; strength: detailed information and large samples
• C. Only genetic databases; strength: precise genotype data
• D. Social media polls; strength: real-time updates

Answer: (B)

In cohort studies, you want data sources that give a clear picture of who was exposed and what happened to them over time. Medical records, registries, and questionnaires are commonly used because they provide both follow-up information and a mix of detailed outcomes and exposures. Medical records offer objective clinical events with diagnoses, treatments, and dates. Registries collect standardized outcomes across large populations, enabling long-term tracking and large sample sizes. Questionnaires add information on exposures, behaviors, and other factors that may not appear in records, such as lifestyle or environmental factors. Together, this mix yields rich, detailed data on many participants, which boosts statistical power and allows for careful adjustment for potential confounders.

Other options don’t fit as well for cohort studies. Relying only on questionnaires gives rapid data collection but often lacks objective outcome verification. Genetic databases provide precise genotype information but typically don’t capture the broad range of clinical outcomes and long-term follow-up needed for cohort analyses. Social media polls offer real-time sentiment or self-reported data but are not reliable for comprehensive, longitudinal exposure and outcome data.