Loss of lean body mass affects low bone mineral density in patients with rheumatoid arthritis - results from the TOMORROW study

Objectives: Osteoporosis is one of the complications for patients with rheumatoid arthritis (RA). Rheumatoid cachexia, the loss of lean body mass, is another. However, the relationship between decreased lean body mass and reduced bone mineral density (BMD) in patients with RA has not been well studied.Methods: This study included 413 participants, comprising 208 patients with RA and 205 age- and sex-matched healthy volunteers. Clinical data, BMD, bone metabolic markers (BMM) and body composition, such as lean body mass and percent fat, were collected. Risk factors for osteoporosis in patients with RA including the relationship BMD and body composition were analyzed.Results: Patients with RA showed low BMD and high BMM compared with controls. Moreover, lean body mass was lower and percent fat was higher in patients with RA. Lean body mass correlated positively and percent fat negatively with BMD. Lean body mass was a positive and disease duration was a negative independent factor for BMD in multivariate statistical analysis.Conclusion: BMD and lean body mass were significantly lower in patients with RA compared to healthy controls. Lean body mass correlated positively with BMD and decreased lean body mass and disease duration affected low BMD in patients with RA.Trial Registration: [UMIN Clinical Trials Registry, http://www.umin.ac.jp/ctr/, UMIN000003876].