Associations between Serum 25-Hydroxyvitamin D Concentration and Physical Performance in Old-Old People Living in a Northern Area of Japan

Purpose: The present study aimed to investigate the relationship between serum 25-hydroxyvitamin D [25(OH) D] levels and physical performance, including muscle strength, balance, and gait speed, in older individuals living in a northern area of Japan (latitude approximately 43°north). Subjects: This was a cross-sectional analysis of 273 community-based older individuals (160 women; mean age, 80.0 years), who participated in the “Population-based and Inspiring Potential Activity for Old-old Inhabitants (PIPAOI)”study. Methods: We collected blood samples to determine serum 25(OH) D levels, and we assessed physical performance according to hand grip strength, knee extensor strength, static standing balance, hip walking distance, normal walking speed, and the results of the Timed-Up-and-Go (TUG) test. The other variables were fall experience in the year prior to the study, the Tokyo Metropolitan Institute of Gerontology Index of Competence (TMIGIC), frequency of going outdoors, sun exposure, and exercise habits. Correlations between serum 25(OH) D levels and physical performance as well as other variables were assessed using Pearson’s and Spearman’s correlation analyses. We performed an analysis of covariance (ANCOVA) controlled for age, sex, body mass index, sun exposure, and exercise habits to minimize the influence of confounders on physical performance. Results: We found significant associations between serum 25(OH) D levels and sex (rs=-0.19), bone density as measured by speed of sound in bone (r=0.16), grip strength (r=0.19), frequency of going outdoors (rs=0.16), sun exposure (rs=0.25), and TMIGIC (rs=0.15). After controlling for age, sex, BMI, sun exposure, and exercise habits, total length of the center of gravity of participants with 25(OH)D insufficiency were significantly longer than those of participants with sufficient 25(OH)D levels (p<0.05). Conclusion: Our results suggest that it is important for community-based older individuals to maintain sufficient 25(OH) D levels in order to avoid lowering physical performance.