Abstract
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.
Highlights
Vitamin D plays a major role in the regulation of calcium homeostasis and bone metabolism [1]
Vitamin D deficiency, which can result from inadequate exposure to sunlight coupled with inadequate dietary intake, plays an important role in the development of osteoporosis because it induces secondary hyperparathyroidism that leads to the mobilization of calcium from bone [3]
Some reports suggested that low levels of serum 25-hydroxyvitamin D [25(OH)D] are common amongst older populations, the prevalence of vitamin D deficiency varies considerably depending on geographic location and season [4,5,6,7]
Summary
Vitamin D plays a major role in the regulation of calcium homeostasis and bone metabolism [1]. Production of vitamin D in the skin is attributable to ultraviolet B conversion of 7-dehydrocholesterol to vitamin D3 This is hydroxylated in the liver and kidney to 1,25 dihydroxy-vitamin D3[1,25(OH)D3] under the control of endocrine factors, including parathyroid hormone (PTH), and the ionic effects of calcium and phosphate concentrations [2]. It regulates the blood levels of calcium and phosphorus by promoting their absorption from food in the intestine and calcium and phosphorus are essential for bone formation and mineralization and the development of a strong skeleton [3]. Some reports suggested that low levels of serum 25-hydroxyvitamin D [25(OH)D] are common amongst older populations, the prevalence of vitamin D deficiency varies considerably depending on geographic location and season [4,5,6,7]
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