Objectives This study systematically compared accumulation, sensitive period, critical period and social mobility models relating life course socioeconomic position (SEP) and adult crystallised cognitive ability, which has not been comprehensively investigated.
Design Two prospective cohort studies.
Participants Five thousand three hundred and sixty-two participants in the Medical Research Council National Survey of Health and Development (NSHD) Birth Cohort Study and 10 308 participants in the Whitehall II Occupational Cohort Study.
Measures Childhood SEP was measured by father’s occupational SEP, early adulthood SEP by educational qualifications and adult SEP by own occupational SEP. Each life course model was compared with a saturated model.
Results Using multiple imputation to account for missing data, the sensitive period model, which contained childhood, early adulthood and adult SEP terms, with different coefficients, provided the best fit for both men and women in the NSHD and Whitehall II cohorts. Early adulthood SEP had the largest coefficient in NSHD women, whereas for NSHD men early adulthood and adult SEP had similar coefficients. In Whitehall II adult SEP had the largest effect size for both men and women.
Conclusions Sensitive period with all three time periods was the most appropriate life course models for adult crystallised cognitive ability in both cohorts, including an effect of childhood SEP. It is important to directly compare the life course models to determine which is the most appropriate.
- cioeconomic position
- cognitive function
- life course
- cohort studies
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Acknowledgements The authors thank the NSHD Study members for their continuing support and members of the NSHD scientific and data collection teams, and all participating women and men in the Whitehall II Study, as well as all Whitehall II research scientists, study and data managers and clinical and administrative staff who make the study possible.
Contributors RL co-designed the study and the analytical plan, analysed the data and drafted the manuscript. JH co-designed the study's analytical plan, and critically revised the manuscript. MR helped focus and direct the study, and critically revised the literature review and Discussion section. RH co-designed the study and the study's analytical plan, and critically revised the manuscript.
Funding RL was supported by an ESRC PhD studentship at University College London. The UK Medical Research Council, British Heart Foundation and the US National Institutes of Health(R01HL36310, R01AG013196) have supported collection of data in the Whitehall II Study. JH is partially supported by the Economic and Social Research Council (ES/K01336X/1). The MRC National Survey of Health and Development, MR and RH are funded by the UK Medical Research Council (MC_UU_12019/1, MC_UU_12019/2, MC_UU_12019/3).
Competing interests None declared.
Ethics approval Ethical approval for NSHD data collection at age 53 years was issued by North Thames Multi-centre Research Ethics Committee (MREC 98/1/121). Ethical approval for the Whitehall II study was obtained from the University College London Medical School Committee on the ethics of human research. All participants provided written informed consent.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Whitehall II and NSHD data, protocols, and other metadata are available to bona fide researchers for research purposes. Please refer to the Whitehall II data sharing policy and the National Survey of Health and Development data sharing policy.
Correction notice This paper has been amended since it was published Online First. Owing to a scripting error, some of the publisher names in the references were replaced with 'BMJ Publishing Group'. This only affected the full text version, not the PDF. We have since corrected these errors and the correct publishers have been inserted into the references.
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