Low Lean Mass Predicts Incident Fractures Independently From FRAX: a Prospective Cohort Study of Recent Retirees.

Whether low muscle mass predisposes to fracture is still poorly understood. In the diagnosis of sarcopenia, different thresholds for low lean mass have been proposed but comparative data for these criteria against hard outcomes such as fractures are lacking. This study aimed to investigate the prevalence of low lean mass according to different thresholds used in operational definitions of sarcopenia and their association with 3-year fracture incidence in a cohort of healthy 63- to 67-year-old community dwellers. In a longitudinal analysis of 913 participants (mean age 65.0 ± 1.4 years) enrolled in the Geneva Retirees Cohort (GERICO) study, lean mass was assessed by dual-energy X-ray absorptiometry (DXA), and low trauma clinical fracture incidence was recorded over a 3-year period. Prevalence of low lean mass ranged from 3.5% to 20.2% according to the threshold applied. During a follow-up of 3.4 ± 0.9 years, 40 (4.4%) participants sustained at least one low trauma fracture. After multivariate adjustment including Fracture Risk Assessment Tool (FRAX) probability with femoral neck bone mineral density (BMD), low lean mass, as defined by Baumgartner thresholds, was associated with higher fracture risk (odds ratio [OR], 2.32; 95% CI, 1.04 to 5.18; p = 0.040). It also added significant predictive value beyond FRAX (likelihood ratio test for nested models, 4.28; p < 0.039). No significant association was found for other definition thresholds. The coexistence of sarcopenia and a T-score <-2.5 at spine or hip was associated with a 3.39-fold (95% CI, 1.54 to 7.46; p = 0.002) increase in low trauma fracture risk. In conclusion, low lean mass, as defined by the Baumgartner thresholds, is a predictor of incident fractures in a large cohort of healthy 65-year-old community dwellers, independently of FRAX probability. The increased risk is related to the threshold for low lean mass selected. These findings suggest that identification of sarcopenia should be considered in fracture risk assessment beyond usual risk factors.