Body composition and muscle strength as predictors of bone mineral density in Crohn's disease

Compromised skeletal status is a frequent finding in patients with Crohn's disease (CD), leading to increased fracture risk. Low body weight is associated with bone mineral density (BMD) in CD, although the relative importance of its components, lean and fat mass, is unclear. Muscle strength is also a predictor of BMD in nondiseased populations; however, its association with bone in CD is unknown. We examined the independent effects of body composition and muscle strength on regional and whole-body BMD in a cohort of CD patients. Sixty men and women, aged 22-72 years, with disease duration of 13 +/- 7 years, underwent scanning of the spine, hip, forearm, and whole-body BMD by dual-energy X-ray absorptiometry (DXA). Lean tissue, appendicular muscle mass (AMM), and fat mass were derived by DXA and grip strength by dynamometry. Medical history, medication usage, clinical variables, and nutritional intake were obtained by questionnaire. Prevalence of osteopenia and osteoporosis was 32 and 17%, respectively, with osteopenia more common at the hip and osteoporosis more common at the spine. In multiple regression analyses, AMM was an independent predictor of whole-body and regional BMD whereas lean mass was an independent predictor at the hip. Neither grip strength nor fat mass was independently associated with BMD. Of the components of body composition, muscle mass was strongly associated with regional and whole-body BMD. Preserving or augmenting muscle mass in this population may be a useful strategy to preserve BMD and thereby reduce fracture risk.