Cohort Profile: The Stockholm birth cohort of 1953

Abstract

The Stockholm Birth Cohort Study (SBC) was created in 2004/ 2005 by a probability matching of two comprehensive and longitudinal datasets. The first, the Stockholm Metropolitan study 1953–1985, consists of all children born in 1953 and living in the Stockholm metropolitan area in 1963. The second, The Swedish Work and Mortality Database 1980–2002 (WMD), consists of all individuals living in Sweden in 1980 or 1990, and born before 1985. The initiative to create the database was taken by Denny Vagero at the Centre for Health Equity Studies, CHESS, of Stockholm University/Karolinska Institute and Sten-Ake Stenberg at the Swedish Institute for Social Research, Stockholm University (SOFI). We refer to the resulting database as the SBC, which in effect provides a 50 year long follow-up of the original 1953 birth cohort. Project Metropolitan began in 1964 on the initiative of the late professor Kaare Svalastoga at the Institute of Sociology, University of Copenhagen. Towards the end of the 1950s he tried to persuade Nordic researchers of the desirability of longitudinal cohort studies. The studies should have a prospective design and cover the period from early school age to early middle life. Svalastoga’s initiative was only successful in Denmark and Sweden. Details of the Danish study are published in an accompanying profile in this issue of the Journal. At Stockholm University professor Carl-Gunnar Janson shouldered the task and began to collect data for the cohort. Fortunately, in contrast to Svalastoga’s recommendations, professor Janson decided to include not only boys but girls also. Data was de-identified in May 1986, after which no more information could be included. In 2002 all data were moved to the Swedish Institute for Social Research in order to better document the study and to explore more fully its research potential. The Work and Mortality Database (WMD) is a temporary database without any personal identification, created at CHESS in 2003 to allow a study of how work, income, and labour market position combine to influence health, disease, and mortality. Both datasets are anonymous and without personal identification codes. However, we realized that the two datasets included a number of identical variables, presumably derived from the same sources, that could be used to combine the two datasets. This gave rise to the hope that we would be able to create a new 1950s birth cohort, following the examples of the revitalized studies in Copenhagen and Aberdeen (both profiled in this issue of the journal). A very large amount of work went into tracing historical documentation and classification procedures of the original data for those variables that were identical in both registries and, therefore, could serve as the basis for a matching algorithm. Ethical permission from the Stockholm Regional Ethics committee as well as ethical rules imposed by the National Board of Health and Welfare and by Statistics Sweden was a necessary precondition before the probability matching was eventually performed in 2004. Consistency checks and documentation are still taking place. Analysis on this new dataset has barely begun. The original Metropolitan study was financed by the Bank of Sweden Tercentenary Foundation during the 21 year period, 1966–86, mostly as grants to collect and organize the data. Professor Janson’s research on Metropolitan data was also financed by the Swedish Council for Planning and Coordination of Research (1986–92), the Commission for Social Research (1986–90), the Foundation Wenner-Grenska samfundet (1991), the Bank of Sweden Tercentenary Foundation (1991–96), the Swedish Council for Social Research (1992–95), and the Swedish Council for Humanistic and Social Sciences (1997–2002). Documentation and creation of the SBC has received financial support from the Swedish council for working life and social research and from the Swedish Research Council, including its longitudinal committee.