Abstract
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<0. 001) and lower sleep fragmentation (p=0. 002) than Asians. There was a higher outdoor light exposure (over 1000 lux) in premenopausal and postmenopausal Caucasians than in same-age Asians (p=0. 052). Qualitative analysis of interview data suggested that religious and cultural influences on family, work and community life may partly explain the reduced sunlight exposure in South Asian women, which contributes to vitamin D deficiency. The implications of this work are that older South Asian women are in need of intervention to improve vitamin D status. There is also some evidence for poorer musculoskeletal health, lower light exposure and poorer sleep in this group. The qualitative research included in the current study offers future intervention options to improve the health of UK dwelling South Asian women.