Population-based cohorts of the 50s and over: a summary of worldwide previous and ongoing studies for research on health in ageing.

As most countries face the ageing of their population, understanding successful and pathologic ageing is a research priority. Longitudinal studies examining the ageing process from middle-age are required to establish causal and valid relationships. This systematic review of the literature aimed at identifying large community-based longitudinal studies either including exclusively elderly people or following people from middle-age (50+ years at enrolment) to death, and resulted in a selection of 72 cohort studies. Design features of selected studies show that most were conducted in North America or Northern Europe, most included both genders, and follow-up period was often less than 10 years. Many cohorts focused on cardiovascular health, cognitive decline or osteoporosis. Usually collected variables comprise of self-reported data on socio-demographics, chronic diseases and functional status, as well as measures of cognition, anthropometrics and physical performances. Biological samples were taken in about 60% of the studies, and a third also undertook genetic analyses. This review summarises information on design and content of large population-based cohorts of older persons, and represents a valuable background from which additional data may be retrieved.