Objectives The authors aimed to test the relationship between childhood cognitive function and long-term sick leave in adult life and whether any relationship was mediated by educational attainment, adult social class or adult mental ill-health.
Design Cohort study.
Setting The authors used data from the 1946, 1958 and 1970 British birth cohorts. Initial study populations included all live births in 1 week in that year. Follow-up arrangements have differed between the cohorts.
Participants The authors included only those alive, living in the UK and not permanent refusals at the time of the outcome. The authors further restricted analyses to those in employment, full-time education or caring for a family in the sweep immediately prior to the outcome. 2894 (1946), 15 053 (1958) and 14 713 (1970) cohort members were included. Primary and secondary outcome measures: receipt of health-related benefits (eg, incapacity benefit) in 2000 and 2004 for the 1958 and 1970 cohorts, respectively, and individuals identified as ‘permanently sick or disabled’ in 1999 for 1946 cohort.
Results After adjusting for sex and parental social class, better cognitive function at age 10/11 was associated with reduced odds of being long-term sick (1946: 0.70 (0.56 to 0.86), p=0.001; 1958: 0.69 (0.61 to 0.77), p<0.001; 1970: 0.80 (0.66 to 0.97), p=0.003). Educational attainment appeared to partly mediate the associations in all cohorts; adult social class appeared to have a mediating role in the 1946 cohort.
Conclusions Long-term sick leave is a complex outcome with many risk factors beyond health. Cognitive abilities might impact on the way individuals are able to develop strategies to maintain their employment or rapidly find new employment when faced with a range of difficulties. Education should form part of the policy response to long-term sick leave such that young people are better equipped with skills needed in a flexible labour market.
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To cite: Henderson M, Richards M, Stansfeld SA, et al. The association between childhood cognitive ability and adult long-term sickness absence in three British birth cohorts: a cohort study. BMJ Open 2012;2:e000777. doi:10.1136/bmjopen-2011-000777
Contributors MH, MH and SS conceived the study. MH, MH and MR analysed the data. MH, MH, SS and MR interpreted the results. MH drafted the manuscript. MH, SS and MR critically revised the manuscript for important intellectual content. All authors approved the final version. MH is the guarantor.
Funding Dr MH received support from a Medical Research Council Research Training Fellowship in Health Services and Health of the Public Research. He is now supported by the NIHR Biomedical Research Centre BRC Nucleus jointly funded by the Guys and St Thomas' Charity and the South London and Maudsley Trustees. Professor MH is supported by the NIHR Biomedical Research Centre for Mental Health at the South London and Maudsley NHS Foundation Trust and Institute of Psychiatry, Kings College London. All authors confirm that this research was carried out independent of the funders.
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Data from the 1958 and 1970 birth cohorts are publically available. Data from the 1946 birth cohort are available on request (http://www.nshd.mrc.ac.uk/).