Vitamin D, light exposure, sleep and musculoskeletal health in South Asian and Caucasian women: biological and social influences

There is an urgent need to better understand the problem of vitamin D deficiency, and its health effects, in population groups of different ethnicity. The principal aim of this project was to examine vitamin D status, sunlight exposure, and health outcomes in UK dwelling South Asian and Caucasian women. A cohort of 80 postmenopausal and 32 premenopausal South Asian and Caucasian women were assessed for vitamin D status (serum 25-hydroxyvitamin D; 25(OH)D), musculoskeletal health, light exposure and sleep-wake cycles. In postmenopausal women, South Asians had a significantly lower vitamin D concentration than Caucasians (p=0.002), with 83% of Asians vs. 24% of Caucasians below 50nmol/l for 25(OH)D. Despite adaptations in tibial bone structure of the South Asians to improve bone strength, their bones were weaker by 38% compared with Caucasians (p<0.001). Stand-to-walk time (Asian mean (±SD) time 8.1 s ± 1.8 vs. Caucasian mean (±SD) time 6.9 s ± 1.4); p=0.002) and grip strength (Asian strength=70% of Caucasian strength, p<0.001) were worse in the South Asians. For both premenopausal and postmenopausal women, Caucasians showed a significantly higher actigraphic sleep efficiency (p