Impact of BMI on exacerbation and medical care expenses in subjects with mild to moderate airflow obstruction

Background and objective: The rate of obesity is increasing in Asia, but the clinical impact of body mass index (BMI) on the outcome of chronic obstructive pulmonary disease (COPD) remains unknown. We aimed to assess this impact while focusing on the risk of exacerbation, health-care utilization, and medical costs. Methods: We examined 43,864 subjects registered in the Korean National Health and Nutrition Examination Survey (KNHANES) database from 2007 to 2012, and linked the data of COPD patients who had mild to moderate airflow obstruction (n = 1,320) to National Health Insurance (NHI) data. COPD was confirmed by spirometry. BMI was used to stratify patients into four categories: underweight (BMI <18.5 kg/m(2)), normal range (18.5-22.9 kg/m(2)), overweight (23-24.9 kg/m(2)), and obese (>= 25 kg/m(2)). Results: Of the 1,320 patients with COPD with mild to moderate airflow obstruction, 27.8% had a BMI >= 25 kg/m(2). Compared with normal-weight patients, obese patients tended to experience fewer exacerbations (incidence rate ratio [IRR] 0.88; 95% CI 0.770-0.99; P = 0.04), although this association was not significant in a multivariable analysis. COPD-related health-care utilization and medical expenses were higher among underweight patients than the other groups. After adjustment, the risk of COPD-related hospitalization was highest among underweight and higher among overweight patients vs normal-weight patients (adjusted IRRs: 7.12, 1.00, 1.26, and 1.02 for underweight, normal, overweight, and obese groups, respectively; P = 0.01). Conclusion: Decreased weight tends to negatively influence prognosis of COPD with mild to moderate airflow obstruction, whereas higher BMI was not significantly related to worse outcomes.