Sex-specific association of serum vitamin D levels with physical function in older adults

Abstract

In women, but not men, lower 25-hydroxyvitamin D [25(OH)D] levels were associated with impaired performance on two lower extremity function tests in both cross-sectional and prospective analyses.

Introduction: Preserved physical function may explain how 25(OH)D supplementation reduces falls and fractures.

Methods: A total of 1,065 community-dwelling men and women (mean age 74.6 years) with 25(OH)D levels and performance on timed up and go (TUG) and timed chair stand (TCS) were seen in 1997-1999; 769 (72%) participants returned for follow-up. Associations were examined using generalized linear models.

Results: 25(OH)D levels were higher in men than women, but the prevalence of vitamin D insufficiency defined as 25(OH)D <75 nmol/L was 14%. There were no baseline sex differences in TUG or TCS. However, after 2.5 years, decline in TCS and TUG was greater in women than men (11% vs. 3%; p < 0.001). Women in the lowest 25(OH)D quartile (<80 nmol/L) compared to the highest quartile had an accelerated rate of functional decline on the TUG and TCS independent of covariates. No significant associations were seen in men.

Conclusion: In women, but not men, lower 25(OH)D levels were associated with impaired performance on two lower extremity function tests in both cross-sectional and prospective analyses. These results provide additional evidence that 25(OH)D is associated with physical function, which may explain how vitamin D supplementation reduces falls and fractures.

Figure 1. 25-hydroxyvitamin D quartiles and Change in Physical Function (%)

Figure 1 depicts the percent change in physical function by quartiles of 25-hydroxyvitamin D over a 2.5 year follow-up period in older men and women. Physical function were measured by two physical performance tests: 1) Timed Chair Stands (TCS) and 2) Timed Up and Go (TUG). Timed Chair Stands is the time (seconds) it takes to complete 5 chair stands without stopping or using arms to push off. Timed Up & Go is the amount of time (seconds) it takes to rise from a chair, walk 3 meters, and return to a sitting position. Increase time to perform these tests reflected poorer physical performance. Women in the lowest quartile of 25-hydroxyvitamin D had the largest relative increase on the physical function measures.