[Association of Serum Vitamin D with Hand-grip Strength and Balance Ability: a Cross-sectional Study on Community-dwelling Women in Sichuan, China]

Objective: To determine the relationship between serum levels of 25(OH)D and 1, 25(OH)₂ D and the hand-grip strength and balance ability of women in Sichuan, China.

Methods: A cross-sectional study on a representative sample of 1 095 women aged 29-95 yr. in Sichuan Province was undertaken. Their hand-grip strength and balance ability were assessed using a hand-held dynamometer and the short physical performance battery (SPPB), respectively. The participants were divided into four groups according to the level of serum 25(OH)D: sufficient (>75 nmol/L), insufficient (51-75 nmol/L), deficiency (25-50 nmol/L), and serious deficiency (<25 nmol/L). General liner models were established to compare the differences of the four groups in balance ability. Logistic regression models were established to examine the associations of serum 25(OH)D and 1, 25(OH)₂ D withhand-grip strength and physical performance.

Results: About 70.9% of the participants had vitamin D deficiency. Those with vitamin D insufficiency or deficiency were more likely to reside in a higher latitudinal area (P<0.001), spend less time in outdoor activities (P=0.013), and take less vitamin D supplements (P<0.001). Older women (≥65 years) had lower serum 25(OH)D (P=0.001) and were more likely to have ≤50 nmol/L 25(OH)D than their younger counterparts (74.6% vs. 68.9%, P=0.046). However, no significant age differences were found in serum 1, 25(OH)₂ D. Serum levels of 25(OH)D and 1, 25(OH)₂ D were not found to be associated with hand-grip strength and balance ability after adjusting for confounding factors. Hand-grip strength and balance ability decreased with age (OR=1.066, P<0.001; OR=1.111, P<0.001). Higher body mas was associated with higher hand-grip strength (OR=0.958, P<0.001). Higher serum albumin (OR=0.896, P=0.001) and longer walking time (OR=0.799, P=0.001) were associated with higher balance ability.

Conclusion: Serum levels of 25(OH)D and 1, 25(OH)2D are not associated with hand-grip strength and balance ability.