Vitamin D, muscle strength and function in South Asian women aged ≥ 60 years living in the North of England: a cross-sectional observational study.

Purpose: The importance of vitamin D is well established for bone health and there is some evidence that inadequate/deficient vitamin D status is associated with reduced skeletal muscle strength and physical function in older adults. Most of this evidence for the muscular effect has come from white population groups and the evidence base is sparse for other ethnic groups. This study investigates the relationship between vitamin D status, muscle strength and function in UK South Asian women aged ≥ 60 years.

Methods: This cross-sectional study included 120 community-dwelling Indian and Pakistani women, aged ≥ 60 years living in the North of England. Circulating blood 25(OH)D concentration was assessed by HPLC-MS using finger prick blood samples; functional capacity was assessed using handgrip strength, single and repeated chair stands, timed up and go, and balance test. Regression analysis was used to analyse the relationships between vitamin D status and muscle strength and function.

Results: The median (IQR) age of the women was 66 (64-73) years. Forty-seven percent of the women were vitamin D inadequate/deficient. Around forty-one percent of the women reported taking a daily vitamin D supplement, 86% of whom were vitamin D sufficient (≥ 50 nmol/L). In non-vitamin D supplement users 32% were vitamin D sufficient. Women with vitamin D sufficiency had significantly better single chair stand (p = 0.045), repeated chair stand (p = 0.01), and balance (p = 0.040) test than those with deficiency/inadequacy. No difference was observed in handgrip strength and timed up and go.

Conclusion: In this group of South Asian women aged ≥ 60 years, vitamin D deficiency/inadequacy was common in those not taking vitamin D supplements. Inadequate/deficient vitamin D status was associated with poor performance of lower limb muscle function, but no association was found with handgrip strength and timed up and go. The associations between supplementation, vitamin D status and lower limb strength helps support a rationale for targeted supplementation in this population of older UK South Asian women.