Osteoporosis and Determinants of Bone Density in Patients with Crohn's Disease

Low bone mineral density (BMD) is common inpatients with Crohn's disease; however, the pathogenesisof bone loss and risk factors for osteoporosis are notestablished. Our aim was to evaluate the clinical, dietary, and nutritional determinants of BMD inCrohn's disease. A cross-sectional analysis of 117patients with Crohn's disease was undertaken. Allpatients underwent a clinical and dietary evaluation including assessment of nutritional state andlife-style. BMD was measured at the hip and lumbar spineby dual-energy x-ray absorptiometry; and z scoresobtained by comparison with age- and sex-matched normal values for the healthy UK population.Multiple regression analysis was used to assessassociations between BMD and potential risk factors,allowing for possible confounding variables. Thirteen(11%) patients had osteoporosis (z score<–2), with osteopenia (z score <–1,>–2) in a further 34 (29%). Patients withjejunal disease had significantly lower BMD at the spine(P = 0.03) and femoral neck (P = 0.02) than those with disease atother sites. Mean BMD was significantly lower at the hipof patients with previous bowel resection (diff in means= 0.53, 95% CI-0.97, –0.08, P = 0.02), but type of surgery was not significant. Active disease,menstrual history, diet, level of physical activity, andsmoking were not associated with low bone mass. At thelumbar spine, body weight (P < 0.0001), male sex (P < 0.0001), and currentprednisolone use (P < 0.02) were independentlypredictive of low bone mass. Body weight (P <0.0001), male sex (P < 0.0001), and cumulativesteroid dose (P = 0.02) were predictive at the femoralneck. The major determinants of BMD in Crohn's diseaseare body weight, current steroid use, and cumulativesteroid dose. Men with Crohn's disease are at greatest risk of osteoporosis, with jejunal involvementand previous bowel resection also contributing to thelow bone mineral density.