Not All Elderly People Benefit From Vitamin D Supplementation with Respect to Physical Function: Results From the Osteoporotic Fractures in Men Study, Hong Kong.

Objectives To examine vitamin D status and its association with physical performance and muscle mass in older Chinese men. Design Cross-sectional and prospective cohort study design. Setting Hong Kong, People's of Republic of China. Participants Nine hundred thirty-nine community-dwelling men aged 65 and older for cross-sectional analysis and 714 for longitudinal analysis. Measurements Baseline serum 25-hydroxyvitamin D (25 OHD) was measured using a competitive radioimmunoassay kit. Baseline and 4-year physical performance measures (grip strength, 6-m walking speed, step length in a 6-m walk, time to complete five chair stands) were measured, and appendicular skeletal muscle mass ( ASM) was assessed using dual-energy X-ray absorptiometry. Data were collected for confounding factors: demographic, number of diseases, smoking, alcohol use, body mass index, physical activity, diet, season of blood sampling, and serum parathyroid hormone ( PTH) level. Multivariate regression analyses were performed with adjustments for confounding factors. Results Mean ± standard deviation serum 25 OHD level of this sample of Chinese community-dwelling older men who had a high level of baseline physical function was 77.9 ± 20.5 nmol/L; 94.1% of participants had serum 25 OHD levels of 50 nmol/L or greater. Median (interquartile range) serum PTH level was 4.1 pmol/L (3.1-5.5 pmol/L). After adjustment for potential confounding factors, serum 25 OHD levels were not associated with baseline or 4-year change in physical performance measures and ASM. Conclusion In Chinese older men who are vitamin D replete and have a high level of baseline physical function, vitamin D may not have an important role in physical function and muscle mass. [ABSTRACT FROM AUTHOR]