Background: Patients with Crohn's disease (CD) are 1.4 to 2.5 times more likely than the normal population to sustain a fracture but the factors involved in the pathogenesis are not clearly understood. Bone mass is affected both by nutrition and by muscular activity. Trauma excepted, the largest voluntary loads on bones come from muscle contraction, not body weight.
Aim: To assess the relationship between bone mass (bone mineral content) and muscle mass (lean mass) in CD patients.
Methods: Adult CD patients who had had a whole body, lumbar and hip densitometric evaluation were selected. Information regarding age, gender, weight, duration of CD, age at diagnosis, use of glucocorticoids and disease activity during the year before densitometric evaluation and laboratory parameters were collected.
Results: Data from 65 patients (28.8+/-10.6 years, F=44, M=21) were analyzed. Lumbar bone mineral content (BMC), BMC in both hips, total and regional BMC significantly correlated with body weight and total and regional lean mass (LM). In multiple regression analysis, only total LM was shown to be independently associated with lumbar BMC, BMC in both hips and total BMC. LM in upper and lower limbs was shown to be independently associated with BMC in upper and lower limbs, respectively.
Conclusions: These results suggest that muscular mass and activity, rather than overall body weight, are important determinants of bone mass and, hence of bone strength in Crohn's disease. Thus, the management of bone loss in inflammatory bowel disease should address the effects of both nutrition and exercise on muscle mass.