Distribution of bone mineral content is associated with body weight and exercise capacity in patients with chronic obstructive pulmonary disease.

Abstract

Background: Although low bone mineral density is highly prevalent in patients with chronic obstructive pulmonary disease (COPD), the distribution of the reduced bone mass has not been fully elucidated. Objectives: To determine regional bone mass loss in patients with COPD and investigate whether the change in distribution may be associated with body weight loss and functional capacity. Methods: Body mass index (BMI) was assessed, and height squared indices were derived for the bone mineral content index (BMCI) of the arms, legs and trunk by dual-energy X-ray absorptiometry in 45 male patients with COPD and 12 age- and sex-matched control subjects. Pulmonary function tests were performed, and maximal oxygen uptake (V·O2max) was measured. Results: The BMCI was lower in the total bone, legs and trunk of patients with COPD than in control subjects, although the BMCI in the arms was similar between the groups. BMI correlated significantly with the BMCI in all 3 segments. Bone mineral content (BMC) in the trunk, expressed as a percentage of total BMC (BMC trunk/total BMC), correlated significantly with BMI. The BMCI in the trunk was closely related with V·O2max but not with airflow limitation. Conclusions: There was a regional difference in BMC reduction, but a predominant reduction of bone mass in the trunk was not associated with the severity of airflow limitation but rather with body weight loss and exercise intolerance. These data suggest that body weight loss and exercise intolerance are important risk factors for vertebral fracture in patients with COPD.