Muscle strength in the elderly: its relation to vitamin D metabolites.

Abstract

To identify a relation between loss of muscle strength and vitamin D deficiency in ambulatory elderly persons not receiving vitamin D supplementation. Cross-sectional study. All measurements were taken at the Department of Geriatrics, University Hospital, Basel, Switzerland. Three hundred nineteen patients (103 women, 216 men) selected by random sampling from participants in an ongoing interdisciplinary study on aging (mean age for women, 74.2 yrs; for men, 76.7 yrs). Leg extension power (LEP) and body mass index (BMI); serum values of 25-hydroxyvitamin D [calcidiol, 25(OH)D], 1,25-hydroxyvitamin D [calcitriol, 1,25(OH)2D], and intact parathyroid hormone (iPHT). Twelve percent of women and 18% of men had 25(OH)D values below the normal range (<12 ng/mL). Muscle strength was lower in older subjects (female: r = -.35; p = .0005/male: r = -.48; p < .0001) and was lower in women than in men (p < .0001). In men both 25(OH)D and 1,25(OH)2D was significantly correlated with LEP (r = 0.24; p = .0004/r = .14; p = .045). In women, only 1,25(OH)2D was significantly correlated with LEP (r = 0.22; p = .034). In an ANCOVA including all participants and explaining LEP by sex, age, BMI, 1,25(OH)2D, 25(OH)D, and iPTH, all factors showed significant effects except 25(OH)D and iPTH (r2 = .41). Muscle strength declined with age in ambulatory elderly people and showed modest, but significant, positive correlation with 1,25(OH)2 vitamin D in both sexes and with 25(OH)D in male subjects. Therefore vitamin D deficiency appears to contribute to the age-related loss of muscle strength, which might be more pronounced in institutionalized elderly people with a high prevalence of vitamin D deficiency.