Prognostic value of weight change in chronic obstructive pulmonary disease: results from the Copenhagen City Heart Study

Abstract

An association between low body mass index (BMI) and poor prognosis in patients with chronic obstructive pulmonary disease (COPD) has been found in a number of studies. The prevalence and prognostic importance of weight change in unselected subjects with COPD was examined. Subjects with COPD, defined as forced expiratory volume in one second/forced vital capacity <0.7 in the Copenhagen City Heart Study and who attended two examinations 5 yrs apart, were followed for 14 yrs for COPD-related and all-cause mortality. The proportion of subjects who lost >1 unit BMI (∼3.8 kg) between the two examinations was significantly associated with level of COPD, reaching ∼30% in subjects with severe COPD. After adjusting for age, smoking habits, baseline BMI and lung function, weight loss was associated with higher mortality in both persons with and without COPD (rate ratio (RR) for weight loss >3 BMI units 1.71 (95% confidence interval (CI): 1.32–2.23) and 1.63 (95% CI 1.38–1.92), respectively). Weight gain was associated with increased mortality, but not significantly so in subjects with COPD. Risk of COPD-related death increased with weight loss (RR 2.14 (95% CI 1.18–3.89)), but not with weight gain (RR 0.95 (95% CI 0.43–2.08)). In subjects without COPD or with mild-to-moderate COPD, the effect of weight change was the same irrespective of initial weight. In subjects with severe COPD, there was a significant risk ratio modification (p=0.045) between effect of baseline BMI and weight change: in the normal-to-underweight (BMI<25), best survival was seen in those who gained weight, whereas for the overweight and obese (BMI≥25), best survival was seen in stable weight. A high proportion of subjects with chronic obstructive pulmonary disease experienced a significant weight loss, which was associated with increased mortality. The results support further intervention studies that aim at avoiding weight loss in normal-to-underweight chronic obstructive pulmonary disease patients.