Can vitamin D deficiency influence muscle performance in postmenopausal women? A multicenter retrospective study.

Background: The presence of the vitamin D receptor (VDR) has been recently demonstrated in human muscle supporting the theory of a role of vitamin D in the proliferation and differentiation of muscle cells. So far only few studies investigated the association between vitamin D and muscle performance in postmenopausal women.

Aim: To define the functional impact of vitamin D deficiency.

Design: Multicenter retrospective study.

Setting: Five Italian outpatient services of Physical and Rehabilitation Medicine (PRM).

Population: Postmenopausal women.

Methods: We divided the population in two groups based on the threshold of 30 ng/mL as cut-off to define sufficient and insufficient serum levels of 25-hydroxyvitamin D3 [25(OH)D3]. Outcome measures were: appendicular lean mass (ALM); ALM-to-BMI ratio (ALMBMI); total fat mass (FM); visceral adipose tissue (VAT); Hand Grip Strength (HGS); Knee Isometric Extension Strength (KES); Short Physical Performance Battery (SPPB); 4-meter gait speed (4MGS).

Results: We analyzed the data records of 401 postmenopausal women (mean age 66.93±8.47 years): 203 with hypovitaminosis D (mean age 66.81±8.11 years) and 198 with normal levels of 25(OH)D3 (mean age 67.04±8.84 years). The analysis showed a significant difference between the two groups in terms of: ALMBMI (0.002), FM (P<0.001), VAT mass (0.010), VAT volume (P=0.006), HGS (P<0.001), KES (P<0.001), SPPB score (P<0.001), percentage of people with a 4MGS≤0.8 m/s (P<0.001). Furthermore, there were significant correlations (P<0.001) between serum levels of 25(OH)D3 and HGS (r=0.323), KES (r=0.510), and SPPB sit to stand (r=-0.362) and walking sub-scores (r=-0.312).

Conclusions: This multicenter study demonstrated that postmenopausal women with vitamin D deficiency had a significant reduction of appendicular muscle strength and physical performance.

Clinical Rehabilitation Impact: This study reported the frequency of hypovitaminosis D in postmenopausal women and its influence on the reduction of muscle mass, strength, and physical performance in a typical population referring to the physiatrist for musculoskeletal disorders.