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.