Vitamin D and muscle strength in patients with previous fractures

To assess the vitamin D status and its association with objective left leg muscle strength measurements in patients with long-bone fracture discharged from a tertiary hospital in Western Australia. The secondary objective was to determine whether tests of balance and functional status are valid predictors of muscle strength and if they correlate with serum 25 hydroxyvitamin D (25OHD) levels.

This was a cross sectional study. Patients who had been discharged from a tertiary hospital following a low impact fracture over a 12-month period were invited to participate. Invitation was through a postal survey audit of osteoporosis risk and treatment and requesting participation in the study. Females over the age of 60 were included. Patients agreeing to participate were invited to attend a research clinic. Patients had demographic data, muscle strength, functional assessments, and biochemical parameters including serum 25OHD assessed.

Of the 99 subjects who completed the study, the mean 25OHD level was 52.0 nmol/L. The main univariate associations with 25OHD were cognitive function, functional indices, sun exposure, albumin, and parathyroid hormone (PTH). In a multivariate model,the strongest and most significant association was between muscle strength and 25OHD levels (r=0.489, p<0.001). Muscle strength was most strongly associated with 25OHD levels >50 nmol/L (r=0.51, p<0.001).

This study demonstrates a significant association between 25OHD levels and left leg muscle strength. This independent association supports the hypothesis that 25OHD deficiency may be responsible for poor muscle strength.