Variations in the vitamin D receptor gene are not associated with measures of muscle strength, physical performance, or falls in elderly men. Data from MrOS Sweden

The vitamin D receptor (VDR) has been proposed as a candidate gene for several musculoskeletal phenotypes. However, previous results on the associations between genetic variants of the VDR with muscle strength and falls have been contradictory. The MrOS Sweden survey, a prospective population-based cohort study of 3014 elderly men (mean age 75 years, range 69-81) offered the opportunity to further investigate these associations. At baseline, data were collected on muscle strength and also the prevalence of falls during the previous 12 months. Genetic association analysis was performed for 7 Single Nucleotide Polymorphisms (SNPs), covering the genetic region surrounding the VDR gene in 2924 men with available samples of DNA. Genetic variations in the VDR were not associated with five different measurements of muscle strength or physical performance (hand grip strength right and left, 6 m walking test (easy and narrow) and timed-stands test). However, one of the 7 SNPs of the gene for the VDR receptor, rs7136534, was associated with prevalence of falls (33.6% of the AA, 14.6% of the AG and 16.5% of the GG allele). In conclusion, VDR genetic variants are not related to muscle strength or physical performance in elderly Swedish men. The role of the rs7136534 SNP for the occurrence of falls is not clear.

Muscle strength correlates with total body bone mineral density in young women but not in men

BACKGROUND

Osteoporosis is a growing health problem. One of the proposed reasons for this is a more sedentary lifestyle. The aim of this study was to investigate the associations between muscle strength and total body bone mineral density (TBMD) in young adults at expected peak bone mass.

METHODS

Sixty-four women and 61 men (total 125) 21 years of age were included. Handgrip strength, isokinetic knee-flexion and -extension muscle strength, TBMD, and body composition were measured.

RESULTS

Univariate regression analyses showed that knee flexion and extension explained almost 30% of the variation in TBMD in women, whereas handgrip strength was not associated with TBMD. In men, no correlation between any measures of muscle strength and TBMD was evident. Stepwise regression analysis showed that knee-flexion and -extension muscle strength in women were associated with TBMD, R2=0.27. In men, lean body mass, fat mass, weight, and height were predictors for TBMD, R2=0.43, whereas muscle strength did not affect the prediction of TBMD.

CONCLUSIONS

Muscle strength at weight-bearing sites is related to TBMD in women, whereas body composition is related to TBMD in men. The association of lower limb strength on TBMD only in young women indicates a gender difference.