Glucocrticoid-induced osteoporosis: is the bone density decrease the only explanation?

Background. Glucocorticoids may increase bone fragility via mechanisms inde pendent from their bone mass reducing effect. Objective. To study relations hips between osteoporotic fractures and bane mineral density in patients on long-term glucocorticoid therapy. Patients and methods. We studied 121 wom en with a mean age of 60.4+/-14.3 years on long-term glucocorticoid therapy (cumulative dose greater than or equal to 1 g of prednisone equivalent, du ration greater than or equal to 6 months) for rheumatoid arthritis (n = 38) , polymyalgia rheumatica or giant cell arteritis (n = 26), connective tissu e disease (n = 15), asthma (n = 14), another inflammatory joint disease (n = 14), or another condition (n = 14). The control group was composed of 125 subjects who had the same mean age and met the same exclusion criteria as the case group. Bone mineral density was measured at the lumbar spine and f emoral neck using a Hologic QDR 4500(R) unit. In subjects with back pain, r adiographs of the thoracic and lumbar spine were obtained to look for fract ures. Results. The odds ratio far a bone mineral density decrease of one st andard deviation at the femoral neck was 1.68 (1.20-2.35) in patients with a cumulative glucocorticoid dose of 10 g of prednisone equivalent and 1.67 (1.22-2.29) in those with a glucocorticoid therapy duration of 2 years. Six ty-eight fractures were recorded in 56 patients (46% of the overall patient group). Even after adjustment on age, glucocorticoid therapy duration, and dose, mean bone mineral density values at the lumbar spine and femoral nec k were significantly lower in the subgroup of patients with fractures than in the subgroup without fractures. Sensitivity and specificity of bone mine ral density at the femoral neck and/or lumbar spine for the diagnosis of ve rtebral fracture and/or peripheral fracture were 73% and 51%, respectively. In the stepwise logistic regression model, factors explaining the presence of fractures were as follows, in hierarchical order: age, absence of calci um/vitamin D supplementation, femoral neck T-score, and glucocorticoid dose . Conclusion. Our data are compelling evidence that bone mineral density is a major determinant of the fracture risk in patients with glucocorticoid-i nduced osteoporosis. (C) 2000 Editions scientifiques et medicales Elsevier SAS.