Low bone mineral density in COPD patients related to worse lung function, low weight and decreased fat-free mass

Abstract

Low bone mineral density is frequently seen in COPD patients. Advanced COPD, low BMI and muscle depletion are risk factors for developing low bone mineral density (BMD). Low bone mineral density is seen in 75% of the GOLD stage IV patients.

Introduction: We set out to investigate the prevalence of low bone mineral density (BMD) in chronic obstructive pulmonary disease (COPD) as well as the predictors of abnormal bone mineral density.

Methods: A cross-sectional design was used to evaluate 115 subjects with COPD (GOLD stages II-IV). Bone mineral density (BMD) was measured using an ultrasound densitometer. The forced expiratory volume in 1 s (FEV(1)) was assessed and fat-free mass was measured using bioelectrical impedance analysis. Chi-square tests and logistic regression were used for analysis.

Results: The prevalence of a T-score < -1.0 SD and > -2.5 SD was 28.6% in GOLD stage II, 40.3% in GOLD stage III and 57.1% in GOLD stage IV. The prevalence of a T-score <or=-2.5 SD was 0% in GOLD stage II, 9.6% in GOLD stage III and 17.9% in GOLD stage IV. In a logistic model FFM, BMI and FEV(1) were significant predictors of abnormal bone mineral density. Patients in GOLD stage IV have a 7.6 times greater risk of abnormal bone mineral density than patients in GOLD stage II.

Conclusions: Low bone mineral density is frequently present in COPD patients. Low FFM, BMI and FEV(1) are risk factors for developing a low T-score. A low FFM or BMI in GOLD stage IV strongly suggests loss of BMD and warrants further examination.