Longitudinal BMI change and Outcomes in Chronic Obstructive Pulmonary Disease: A Nationwide Population-based Cohort Study

Background: Littie is known about the association between longitudinal body mass index (BMI) change and clinical outcomes in patients with chronic obstructive pulmonary disease (COPD). Methods This retrospective cohort study included 116,463 COPD patients aged ≥ 40, with at least one health examination 2 years before and 3 years after COPD diagnosis (January 1, 2014, to December 31, 2019). The main exposure was a BMI percentage change. The primary endpoint was all-cause mortality, and the secondary endpoint was initial severe exacerbation. Results BMI decreased > 5% in 14,728 (12.6%), 80,689 (69.2%) maintained BMI, and 21,046 (18.1%) increased BMI > 5% after COPD diagnosis. Compared to maintenance group, adjusted hazard ratio (aHR) for all-cause mortality was 1.70 in BMI decrease group (95% CI:1.61, 1.79) and 1.13 in BMI increase group (95% CI:1.07, 1.20). In subgroup analysis, longitudinal decrease in BMI showed a stronger effect on mortality as baseline BMI was lower, while an increase in BMI was related to an increase in mortality only in obese COPD patients with aHRs of 1.18 (95% CI: 1.03, 1.36). The aHRs for the risk of severe exacerbation (BMI decrease group and increase group vs. maintenance group) were 1.30 (95% CI:1.24, 1.35) and 1.12 (95% CI:1.07, 1.16), respectively. Conclusions A decrease in BMI over time was associated with an increased risk of all-cause mortality and severe exacerbation in a dose-dependent manner in patients with COPD. This was most significant in underweight patients. Regular monitoring for weight loss might be an important component for COPD management.