Bone turnover markers, bone mineral density and body composition in Tunisian patients with chronic obstructive pulmonary disease

Background: Chronic obstructive pulmonary disease (COPD) is a systemic disease associated to various comorbidities. Osteoporosis, Vitamine D deficiency and denutrition are common in these patients. Aim: Investigate association between bone mineral density, body composition and bone turnover markers in Tunisian patients with COPD and its correlation with the severity of the disease. Methods: Prospective study conducted in a tertiary care hospital in Tunis. Patients with stable COPD were included. Total hip, lumbar spine, and whole-body T-score were measured with dual-energy X-ray absorptiometry (BMD). Osteoporosis was defined as T-score<-2.5. Parameters of body composition (body mass index [BMI], fat mass index [FMI], and fat-free mass index [FFMI]) were assessed using a single-frequency bio-electrical impedance. Biological assessment included: 25-Hydroxy-vitamin D (25-OHD), parathyroid hormone (PTH), blood osteocalcin (OC) (osteoformation marker) and Cterminal Telopeptide of Collagen type I CrossLaps (CL: osteoresorption marker). Results: sixty-five patients (mean age=65.2±9.5 years) were included. Osteoporosis was found in 53.7% of cases. The 25-OHD level was low (<20 µg/l) in 88% of patients. It was correlated with oral corticosteroids (r=-0.61; p < 10-3). OC level was correlated with BMI (r= -0.325, p=0.01), FMI (r=-0.271, p=0.04) and FFMI (r=-0.264, p=0.04). Moreover, CL level was correlated with T-score (r=-0.47, p=0.002) and bone density (r=-0.387, p=0.01). Conclusion: In Tunisian patients with COPD, bone turnover markers are associated to bone mineral density and body composition.