Association between 25-hydroxy vitamin D levels, physical activity, muscle strength and fractures in the prospective population-based OPRA Study of Elderly Women

Abstract

Vitamin D supplements have been used to prevent fractures. The effect may be mediated through increased bone mass, but also through reduced falling propensity. The aim of this study was to evaluate the association between 25-hydroxy vitamin D levels (25OHD), fall-associated variables (including tests of functional performance), and fracture in ambulatory women. At baseline 25OHD was measured in 986 women. Fall-associated variables were investigated at baseline. Fractures were recorded during a 3-year follow-up. Four percent of the women had 25OHD levels below 20 ng/ml (50 nmol/l), and 26% had 25OHD levels below 30 ng/ml (75 nmol/l). 25OHD correlated with gait speed (r =0.17, P <0.001), the Romberg balance test (r =0.14, P <0.001), self-estimated activity level (r =0.15, P <0.001), and thigh muscle strength (r =0.08, P =0.02). During the 3-year follow-up, 119 out of the 986 women sustained at least one fracture. The Cox proportional hazard ratio (HR) (95% confidence interval) for sustaining a fracture during the follow-up was 2.04 (1.04-4.04) for the group of women with 25OHD below 20 ng/ml, in which 9 out of 43 women sustained a fracture. Thirty-two of the 256 women with 25OHD levels below 30 ng/ml sustained a fracture during the follow-up, with a non-significant HR of 1.07 (1.07-1.61). This cohort of elderly, ambulatory women had a high mean 25OHD. A low 25OHD was associated with inferior physical activity level, gait speed and balance. A 25OHD level below 30 ng/ml was not associated with an increased risk of fractures in this study. However, a subgroup of women with 25OHD levels below 20 ng/ml had a tendency to an increased risk of fractures, which may be associated with an inferior physical activity and postural stability.

Cross-sectional association between serum vitamin D concentration and walking speed measured at usual and fast pace among older women: The EPIDOS study

“…(10,(16)(17)(18)(19)(20)(21)(22) It has been shown that ambulation time over an 8-ft walkway correlated with higher serum 25(OH)D concentrations. (10,18) Gerdhem and colleagues (19) also have reported a positive significant linear correlation with usual walking speed in a cohort of 986 elderly women. However, this result was less reliable than previous studies because no adjustments for confounders were made.…”

“…Second, previous studies used different cutoff values for abnormal serum 25(OH)D concentrations ranging from 10 to 30 ng/mL, (10,(16)(17)(18)(19)(20)(21)(22) which also may explain the divergences. From a historical point of view, normal vitamin D concentrations have been defined by the avoidance of adverse health consequences.…”

“…(41) In addition, iPTH already has been associated with usual walking speed in unadjusted models. (17,19) However, the specific roles of vitamin D and iPTH on muscle and locomotion have not yet been fully elucidated. In our study, the existence of an association between 25(OH)D and walking speed, even after adjustment for iPTH effect, sustains the notion of a direct neuromuscular action of vitamin D, especially because iPTH was not associated with walking speed even in the unadjusted linear regression model.…”

“…(16) Compared with muscle strength or balance performance, (5)(6)(7) fewer attempts have been made to explore the association between low chronic serum 25(OH)D concentrations and walking speed. (10,(16)(17)(18)(19)(20)(21)(22) A better understanding of this association is important to further develop interventional clinical studies to assess the effect of vitamin D supplementation on mobility and gait performance and related adverse health consequences. Previous studies showed conflicting results because some of them found a significant positive association, (10,(16)(17)(18)(19)(20) whereas others did not.…”

“…(10,(16)(17)(18)(19)(20)(21)(22) A better understanding of this association is important to further develop interventional clinical studies to assess the effect of vitamin D supplementation on mobility and gait performance and related adverse health consequences. Previous studies showed conflicting results because some of them found a significant positive association, (10,(16)(17)(18)(19)(20) whereas others did not. (21,22) These differences may be related, in part, to the type of walking speed measured.…”