The role of body mass index in acute exacerbations of chronic obstructive pulmonary disease

Background: Low body mass index (BMI) is a strong prognostic marker in stable chronic obstructive pulmonary disease (COPD); however, little is known about its role in acute exacerbations of COPD. Objectives: To determine the prevalence and determinants of low BMI in emergency department (ED) patients with acute exacerbations of COPD, and to examine whether low BMI was associated with more severe acute exacerbations, more intensive ED treatments and worse post-ED outcomes. Methods: A secondary analysis was performed using data from a prospective multicentre cohort study involving 29 ED in the USA and Canada. Using a standard protocol, ED patients with acute exacerbations of COPD were interviewed and their charts reviewed. BMI was calculated using self-reported weight and height. Main outcome measures included hospital admission, post-ED relapse and ongoing exacerbation. Results: 395 patients were enrolled. Their median age was 69 years (interquartile range 62-76); 52% were women. Thirteen per cent (95% CI 10% to 16%) were underweight, 37% normal weight, 27% overweight and 23% were obese. Current smoking was independently associated with underweight (OR 5.4, 95% CI 1.1 to 25.2). In the propensity-matched cohort, there were no significant differences in severity of exacerbation, treatments received in the ED, or short-term clinical outcomes, according to BMI. Conclusions: Low BMI is not uncommon in patients with acute exacerbations of COPD, and current smoking is associated with low BMI in these patients. Unlike its role in stable COPD, BMI appears to have little impact on exacerbation severity, treatments received in the ED, and short-term clinical outcomes in acute exacerbations of COPD.