Association of Muscle Weakness With Post-Fracture Mortality in Older Men and Women: A 25-Year Prospective Study.

Abstract

Osteoporotic fracture increases the risk of premature mortality. Muscle weakness is associated with both increased fracture risk and low bone mineral density (BMD). However, the role of muscle strength in post-fracture mortality is not well understood. This study examines the change of muscle strength measured at quadriceps (QS) before and after fracture and defines the relationship between muscle strength and post-fracture mortality. The study involved 889 women and 295 men (who were participating in the Dubbo Osteoporosis Study) who had at least one low-trauma fracture (ascertained from X-ray reports) after the age of 50 years. Median follow-up time was 11 years (range 1 to 24). To determine the change in muscle strength before and after a fracture, we selected a subset of 344 women and 99 men who had had at least two muscle strength measurements before the fracture event and a subset of 407 women and 105 men who had had at least two measurements after the fracture. During the follow-up period, 366 (41.2%) women and 150 (50.9%) men died. The annual rate of decrease in height-adjusted muscle strength before fracture was 0.27 kg/m (1.85%) in women and 0.40 kg/m (1.79%) in men. Strength loss after fracture was not significantly different from that before fracture. In women, after adjusting for baseline age and BMD, each SD (5 kg/m) lower height-adjusted pre- and post-fracture quadriceps strength was associated with a 27% (hazard ratio [HR] = 1.27; 95% confidence interval [CI] 1.07, 1.50) and 18% (HR = 1.18; 95% CI 1.01, 1.38) increase in post-fracture mortality risk, respectively. Similarly, in men, each SD (5 kg/m) lower height-adjusted pre- and post-fracture QS was associated with increased mortality before fracture (HR = 1.33; 95% CI 1.09, 1.63) and after fracture (HR = 1.43; 95% CI 1.16, 1.78). Muscle weakness accounted for 15% (95% CI 0.05, 0.24) of premature deaths after fracture in women and 23% (95% CI 0.11, 0.35) in men. These results indicate that in the older individuals, lower muscle strength is an independent risk factor for post-fracture mortality. © 2017 American Society for Bone and Mineral Research.