Abstract
Background: Vitamin D affects physical performance in older adults. Its effects on muscles, notably on muscle strength, remain unclear. The objective of this cross-sectional study was to determine whether hypovitaminosis D is associated with triceps brachii muscle fatigability in community-dwelling older women.Methods: A randomized subset of 744 women aged >= 75years from the EPIDOS cohort was categorized into two groups according to triceps brachii muscle fatigability, defined as loss of strength > 5% between two consecutive maximal isometric voluntary contractions. Hypovitaminosis D was defined using consensual threshold values (i.e., serum 25-hydroxyvitamin D concentration [25OHD] <= 10 ng/mL, <= 20 ng/mL, and <= 30 ng/mL). Age, body mass index, comorbidities, use psychoactive drugs, physical activity, first triceps strength measure, hyperparathyroidism, serum concentrations of calcium, albumin and creatinine, season and study centers were used as potential confounders.Results: The prevalence of hypovitaminosis D <= 30 ng/mL was greater among women with muscle fatigability compared with the others (P = .009). There was no between-group difference using the other definitions of hypovitaminosis D. The serum 25OHD concentration was inversely associated with the between-test change in triceps strength (adjusted beta = - 0.09 N, P = .04). Hypovitaminosis D <= 30 ng/mL was positively associated with triceps fatigability (adjusted OR = 3.15, P = .02).Conclusions: Vitamin D concentration was inversely associated with the ability to maintain strength over time in this cohort of community-dwelling older women. This is a relevant new orientation of research toward understanding the involvement of vitamin D in muscle function.