Which data source is NOT a common source for exposure and outcome in cohort studies?

• A. Medical records
• B. Registries
• C. Administrative data
• D. Genetic sequencing data

Answer: (D)

In cohort studies, exposure and outcome data typically come from sources that routinely capture health information over time, such as medical records (diagnoses, lab results, treatments), registries (standardized event data like disease incidence), and administrative data (claims, billing codes, hospitalizations). These sources are widely available, standardized, and well-suited for tracking how exposures relate to outcomes across large groups.

Genetic sequencing data, while increasingly accessible, is not a common data source for defining exposure or outcomes in standard cohort designs. It requires specialized lab work, consent, and analysis, and is mostly used in studies focused on genetic factors, gene-environment interactions, or Mendelian randomization. In typical cohort studies, sequencing data would be used only in specific genetic investigations rather than as a routine source for exposure or outcome.