Vitamin D receptor gene polymorphisms modify the association of serum 25-hydroxyvitamin D levels with handgrip strength in the elderly in Northern China.

OBJECTIVES: The aim of this cross-sectional study was to investigate the association of serum 25-hydroxyvitamin D (25[OH]D) levels and vitamin D receptor (VDR) genotypes with skeletal muscle mass and function in elderly subjects in northern China.

METHODS: A total of 275 men and 510 women, ages 63.1 to 72.5 y, in two randomly selected communities in Beijing were investigated. The investigation included a questionnaire, physical measurements, muscle mass and function measurements, serum 25(OH)D levels, and VDR gene polymorphisms analysis.

RESULTS: In the group with 25(OH)D levels <10.0 ng/mL, the proportion with low handgrip strength was 3.04 times higher than that in the group with 25(OH)D levels >20.0 ng/mL for men (odds ratio: 3.04; 95% confidence interval, 1.13-8.20) but not for women. The general linear model showed that higher 25(OH)D levels and having T allele of Fok1 and the bb genotype of Bsm1 were significantly associated with more handgrip strength. The regression coefficients (β) were 1.80 (P < 0.01), 1.26 (P < 0.01), and 2.90 (P < 0.01), respectively. There was a significant interaction between 25(OH)D and VDR gene polymorphisms for handgrip strength for both Fok1 (β = 2.86; P < 0.01) and Bsm1 (β = 3.14; P = 0.02) after adjustment for potential confounders (sex, age, body mass index, fat mass, physical activity, sun exposure, energy, and protein intake).

CONCLUSIONS: 25(OH)D levels are associated with handgrip strength for men and this relationship could be modified with the interaction between 25(OH)D and VDR gene polymorphisms (Fok1 and Bsm1).