The term population-based is traditionally used to describe a study that involved a defined “general population”, as opposed to hospital-based or occupation-based populations.
Epidemiologic studies have a tacit need to be based in populations, and as such, most epidemiologic studies can be loosely considered population-based.
Population-based cohort studies are a specific category of epidemiology studies in which a defined population is followed up and observed longitudinally to assess exposure and outcome relationships.
Some critics may argue that such studies have yielded little clinical impact recently—unlike decades ago when they helped uncover major cardiovascular risk factors such as smoking, hypertension, and dyslipidemia.