Work-family life courses and BMI trajectories in three British birth cohorts.

BACKGROUND/OBJECTIVES: Combining work and family responsibilities has previously been associated with improved health in mid-life, yet little is known about how these associations change over time (both biographical and historical) and whether this extends to body mass index (BMI) trajectories for British men and women. The purpose of this study was to investigate relationships between work-family life courses and BMI trajectories across adulthood (16-42 years) for men and women in three British birth cohorts. SUBJECTS/METHODS: Multiply imputed data from three nationally representative British birth cohorts were used-the MRC National Survey of Health and Development (NSHD; 1946 birth cohort, n=3012), the National Child Development Study (NCDS; 1958 birth cohort, n=9614) and the British Cohort Study (BCS; 1970 birth cohort, n=8140). A typology of work-family life course types was developed using multi-channel sequence analysis, linking annual information on work, partnerships and parenthood from 16 to 42 years. Work-family life courses were related to BMI trajectories using multi-level growth models. Analyses adjusted for indicators of prior health, birthweight, child BMI, educational attainment and socioeconomic position across the life course, and were stratified by gender and cohort. RESULTS: Work-family life courses characterised by earlier transitions to parenthood and weaker long-term links to employment were associated with greater increases in BMI across adulthood. Some of these differences, particularly for work-family groups, which are becoming increasingly non-normative, became more pronounced across cohorts (for example, increases in BMI between 16 and 42 years in long-term homemaking women: NSHD: 4.35 kg m-2, 95% confidence interval (CI): 3.44, 5.26; NCDS: 5.53 kg m-2, 95% CI: 5.18, 5.88; BCS: 6.69 kg m-2, 95% CI: 6.36, 7.02). CONCLUSIONS: Becoming a parent earlier and weaker long-term ties to employment are associated with greater increases in BMI across adulthood in British men and women.Rebecca Lacey, Anne McMunn, Amanda Sacker and Meena Kumari received funding from the European Research Council (grant number: ERC-2011-StG_20101124, PI: Anne McMunn). Steven Bell also received funding from the European Research Council (grant number: ERCStG-2012-309337_Alcohol-Lifecourse, PI: Annie Britton) and UK Medical Research Council/Alcohol Research UK (MR/M006638/1). Amanda Sacker, Anne McMunn and Meena Kumari additionally received support from the Economic and Social Research Council’s International Centre for Life Course Studies in Society and Health (grant number: ES/J019119/1). DK is supported by the UK Medical Research Council (MC_UU_12019/1). The MRC National Survey of Health and Development is funded by the UK Medical Research Council. Peggy McDonough and Diana Worts were supported by the Canadian Institutes of Health Research grant MOP 119526 and the Social Sciences and Humanities Research Council grant 43512-1267