Osteoporosis, body composition, and bone turnover in ankylosing spondylitis

Objective. To study the prevalence of osteoporosis (OP) and osteopenia in a nkylosing spondylitis (AS) and to investigate the relationship between symp tomatic and structural severity, the indices of bone turnover, and body com position. Methods. Eighty patients with AS were enrolled prospectively: 52 men (65%) and 25 women, mean age 36.7 years +/- 11.5 (range 18-67); they were studied clinically, radiologically, and by dual energy x-ray absorptiometry. Sixty -three underwent biological assessment of bone turnover markers. Results. OP and osteopenia as defined by the World Health Organization (T s core < -2.5 SD and between -1 and -2.5 SD, respectively) were observed in 1 5 (18.7%) and 25 patients (31.2%) at the lumbar spine and in 11 (13.7%) and 33 patients (41.2%) at the femoral neck. respectively. Patients with OP ha d a lower body mass index (BMI) and fat mass percentage. There was a trend to a lower disease duration in patients with OP at the spine than in health y subjects. Bone resorption markers (urinary D-pyridinoline or C-telopeptid e concentrations) were increased in 34 patients (53.9%). Bone turnover mark ers were positively correlated with C-reactive protein concentration and La rsen radiological hip score: they were negatively correlated with Schober i nder; and fat mass percentage. Conclusion. (1) OP is frequent in AS and can be observed in early stages of the disease. (2) Patients with AS are more susceptible to develop OP when they have low BMI. low fat mass percentage, and active and severe disease. OP was observed in parallel with increased bone resorption.