The association between body composition and self-reported co-morbidity in subjects with chronic obstructive pulmonary disease

Background: Differences in body composition are extensively investigated in subjects with COPD as low muscle mass was independently associated with increased morbidity and mortality. Also cardio-vascular co-morbidity is often reported in COPD and the contribution of fat mass in COPD related co-morbidity is gaining interest. We hypothesized that the prevalence of low muscle mass and high fat mass is higher in subjects with COPD compared to a group of current and former smokers without COPD, which result in higher reported cardiovascular co-morbidity in the COPD group. Methods: In 954 subjects with COPD and 955 subjects without COPD, body composition was assessed by bio-electrical impedance analysis and information on self-reported co-morbidity was collected. Participants were stratified for low fat free mass index and high fat mass index (resp. fat free mass index <10 percentile and fat mass index >50 percentile of the subjects without COPD). Results: Subjects with COPD were more likely to have low fat free mass index than current and former smokers without COPD. The prevalence of high fat mass index was comparable between the groups. The percentage of self-reported co-morbidity was higher in subjects with COPD, but only reports of myocardial infarction were disease specific. Conclusion: Low fat free mass index was more common in COPD, but the prevalence of high fat mass index was comparable between subjects with and without COPD. Nevertheless, subjects with COPD reported more myocardial infarction, implying that other factors than the amount of fat mass are involved in the increased co-morbidity in COPD.