Revitalising the Metropolit 1953 Danish male birth cohort: background, aims and design.

Recent research indicates that factors operating during childhood are related to adult health. Thus, longitudinal studies with information on subsequent phases may be key to understanding later health outcomes. The main objective of this paper is to describe the history and design of a Danish birth cohort, and its revitalisation. In 1965, information from birth certificates for 11 591 of a total of 12 270 males born in 1953 in the Metropolitan area of Copenhagen, Denmark were traced. These boys were the study population of a sociological investigation conducted with the aim of describing social mobility. At age 12 years, 9537 of these cohort members completed a questionnaire in school, which included cognitive measures and information on social aspirations and leisure time activities. In 1966 educational performance tests were administered for these boys and, in 1968, mothers of 2890 cohort members were interviewed regarding family social backgrounds. With the establishment of the Civil Registration System (CRS) in 1968, it was possible to identify 11 532 cohort members. In 2002 we began the process of revitalising this study with the aim of investigating the influence of early life factors on later health. We succeeded in ascertaining the vital status of all subjects in the CRS. This showed that 863 subjects had died between 1968 and 2002. Linkages to the Register of Causes of Death, the National Hospital Register, Psychiatric Central Register and Danish Cancer Registry have been completed. In total, 7969 cohort members had been hospitalised for any somatic illness and, according to the Psychiatric Central Register, 1382 men had been admitted to a psychiatric hospital or ward. In the Cancer Registry we found 363 of our study participants. Analyses exploring the influence of social conditions in early life, birth dimensions, and childhood cognition on adult health experience are at various stages of completion. A questionnaire-based postal follow-up survey is planned. Thus, the Metropolit study provides an important opportunity to examine the processes by which factors that operate over the life course influence adult health.