Working patterns and vitamin D status in mid-life: a cross-sectional study of the 1958 British birth cohort

Objectives To assess the association between working patterns and vitamin D status in men and women and to determine the potential influence of related lifestyle and socioeconomic factors. Methods The authors used data from the 1958 British birth cohort (aged 45 years) and 6154 participants, who were in full-time work, were included in current analyses. Vitamin D status was measured by circulating concentrations of 25-hydroxyvitamin D (25(OH) D). Information on working patterns and lifestyle factors was obtained using a structured questionnaire administered at 45 years. Results Manual social class was strongly associated with vitamin D-related lifestyle factors, with those in manual classes not only spending more time outdoors, but also spending more time watching TV/using PC, consuming less supplements and oily fish. Associations between working patterns and vitamin D-related lifestyles were less clear: night work was not strongly associated with lifestyles in either gender, while working hours were associated with time spent outside, PC/TV leisure time and use of supplements in men but not in women. In men, working patterns were not associated with lower 25(OH) D concentrations. In women, 25(OH) D concentrations were 8% lower (95% CI 15% to 2%) in night workers compared with others, while women working less than 35 h/week had 5% higher concentrations of 25(OH) D (95% CI 1% to 8%) compared with those working 35-40 h/week after adjustment for season, social class and body mass index (BMI). Conclusions Women working nights and longer hours may be vulnerable to deficits in vitamin D status and associated health hazards.