Association of hypovitaminosis D with triceps brachii muscle fatigability among older women: Findings from the EPIDOS cohort
Introduction
Lower concentrations of 25-hydroxyvitamin D (25OHD) are very common in elderly population living in institutions or in the community, reaching up to 90% of older adults [1]. The clinical relevance is that hypovitaminosis D is accompanied by adverse health events. For instance, hypovitaminosis D is associated with poorer physical performance in older adults [2,3]. The explanation most commonly offered is based on the possible involvement of vitamin D in muscle health and function [3], as suggested by experimentation reporting the presence of vitamin D receptors (VDRs) in muscle cells [4]. However, it is noticeable that previous clinical studies on hypovitaminosis D and muscle strength have shown conflicting results [5]. Some cross-sectional studies reported decreased muscle strength in the case of hypovitaminosis D [6,7], although others did not find any significant association [8,9]. Moreover, a meta-analysis of interventional trials showed that vitamin D supplementation could not enhance muscle strength after 9 months of supplementation on average [5]. The latter result weakened the plausibility of a link between vitamin D and muscle strength, and strengthened the assumption that vitamin D may impact muscles in a different way.
Muscle strength is inversely related to fatigue [10]. Mechanistically, while the strength depends on the mass of striated muscles, the fatigability (i.e., the muscle ability to continue effort and maintain constant work over time) depends mainly on muscle mitochondrial function. Mitochondrial cofactors enhance the synthesis of ATP, act as a powerful anti-radical, and reduce the level of lactic acid thereby decreasing muscle fatigue [11]. Interestingly, recent findings suggest that vitamin D is involved in mitochondrial oxidative function in skeletal muscles [12]. Specifically, Sinha et al. reported that the energy production during the recovery phase of modest exercise by muscle mitochondria is impaired among people with hypovitaminosis D [12]. Thus, as mitochondrial oxidative phosphorylation is the primary source of cellular ATP, itself source of energy for the myosin-adenosin system in the striated muscle, the suboptimal mitochondrial function accompanying hypovitaminosis D may lead to greater fatigability [12].
We hypothesized that vitamin D status could influence muscle fatigability in older adults. We had the opportunity to examine the association of serum 25OHD concentration with muscle fatigability in a randomized sample of healthy women aged 75 years and older from the large representative community-based EPIDémiologie de l’OStéoporose (EPIDOS) cohort. The objective of the present cross-sectional analysis was to determine whether hypovitaminosis D was associated with triceps brachii muscle fatigability in older women.
Section snippets
Participants
We studied 744 older women, a randomized subset of the EPIDOS study, a French observational prospective multicentric national cohort designed to evaluate the risk factors for hip fracture among community-dwelling older women. Sampling and data collection procedures have been described in detail elsewhere [13]. In summary, from 1992 to 1994, 7598 women aged 75 years and older were recruited from electoral lists in five French cities (Amiens, Lyon, Montpellier, Paris and Toulouse). Study
Results
Among 744 women included in the present analysis (mean age 80.0 ± 3.5 years), the prevalence of muscle fatigability was 17.5%. The mean 25OHD concentration was 17.9 ± 11.0 ng/mL. Hypovitaminosis D ≤30 ng/mL was retrieved among 671 women, ≤20 ng/mL among 516 women, and ≤10 ng/mL among 127 women.
As indicated in Table 1, the prevalence of hypovitaminosis D ≤30 ng/mL was greater among women with muscle fatigability compared to those without (respectively 96.2% versus 88.9%, P = .009). In contrast,
Discussion
The main result of this population-based study in 744 older women was the finding of an inverse association between serum 25OHD concentration and change of triceps strength between two consecutive measurements; hypovitaminosis D ≤30 ng/mL being independently associated with greater triceps fatigability.
Despite increasing evidence on the effects of vitamin D on muscle health [2] and chronic fatigue syndrome [9,12], only few data are available on the relationship between hypovitaminosis D and
Contributors
G. Duval undertook analysis and interpretation of data, and drafted the manuscript.
Y. Rolland undertook critical revision of the manuscript for important intellectual content.
A.M. Schott was responsible for obtaining funding and acquisition of data, provided administrative and technical support, and undertook critical revision of the manuscript for important intellectual content.
H. Blain undertook critical revision of the manuscript for important intellectual content.
P. Dargent-Molina undertook
Conflict of interest
All authors declare that they have no conflict of interest.
Funding
This work was supported by the French Ministry of Health. The sponsor had no role in the design and conduct of the study, in the collection, management, analysis, and interpretation of the data, or in the preparation, review, or approval of the manuscript.
Ethical approval
Participants were included after having given their written informed consent for research. The study was conducted in accordance with the ethical standards set forth in the Helsinki Declaration (1983). The project was approved by the local ethics committee of each center.
Provenance and peer review
Peer review was directed by Leon Flicker independently of Cedric Annweiler, an author and Maturitas editor, who was blinded to the process.
Research data (data sharing and collaboration)
There are no linked research data sets for this paper. Data will be made available on request.
Acknowledgments
Investigators of EPIDOS study. Coordinators: Breart, Dargent-Molina, Meunier, Schott, Hans, and Delmas. Principal investigators: Baudoin and Sebert (Amiens); Chapuy and Schott (Lyon); Favier and Marcelli (Montpellier); Hausherr, Menkes and Cormier (Paris); Grandjean and Ribot (Toulouse).
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