Association between vitamin D receptor gene polymorphisms, falls, balance and muscle power: results from two independent studies (APOSS and OPUS).

SUMMARY: Fall prevention is a key strategy for reducing osteoporotic fractures. We investigated the association between vitamin D receptor (VDR) polymorphisms and reported falls in postmenopausal women. Bsm1 polymorphisms were associated with falls, balance and muscle power measurements. These results may explain some of the excess fracture risk associated with VDR in some studies.

INTRODUCTION: Fall prevention is a key strategy for reducing osteoporotic fractures. It has been suggested that vitamin D supplementation may reduce the incidence of falls by reducing body sway and increasing muscle power. The vitamin D receptor gene is a well-studied candidate gene for osteoporosis. We investigated the association between VDR polymorphisms and reported falls in postmenopausal women.

METHODS: Falls data were collected in two separate population cohorts. Five polymorphisms of the VDR gene were analysed (Cdx-2, Fok-1, BsmI, Taq1 and Apa1) in the Aberdeen Prospective Osteoporosis Screening Study (APOSS) cohort. Results found in APOSS were then validated in an independent cohort--the Osteoporosis and Ultrasound (OPUS) study (Bsm1 and Fok1 only), where muscle power and balance were also measured.

RESULTS: Carriers of the 'B' allele (Bsm1) showed an increased risk for falls. In APOSS, this was statistically significant for visit 3 multiple falls (p = 0.047) and for recurrent falls (p = 0.043). Similar results were found in OPUS for visit 1 falls (p = 0.025) and visit 1 multiple falls (p = 0.015). Bsm1 polymorphisms were also associated with balance and muscle power measurements.

CONCLUSIONS: In conclusion, these results demonstrate an association between the Bsm1 polymorphism and risk of falling that may explain some of the excess fracture risk associated with VDR in some studies.