Prognostic value of nutritional status in chronic obstructive pulmonary disease

The association between low body mass index (BMI) and poor prognosis in pat ients with chronic obstructive pulmonary disease (COPD) is a common clinica l observation. We prospectively examined whether BMI is an independent pred ictor of mortality in subjects with COPD from the Copenhagen City Heart Stu dy. In total, 1,218 men and 914 women, aged 21 to 89 yr, with airway obstru ction defined as an FEV1-to-FVC ratio of less than 0.7, were included in th e analyses. Spirometric values, BMI, smoking habits, and respiratory sympto ms were assessed at the time of study enrollment, and mortality from COPD a nd from all causes during 17 yr of follow-up was analyzed with multivariate Cox regression models. After adjustment for age, ventilatory function, and smoking habits, low BMI was predictive of a poor prognosis (i.e., higher m ortality), with relative risks (RRs) in underweight subjects as compared wi th that in subjects of normal weight of 1.64 (95% confidence interval [CI]: 1.20 to 2.23) in men and 1.42 (95% CI: 1.07 to 1.89) in women. However, th e association between BMI and survival differed significantly with stage of COPD. In mild and moderate COPD there was a nonsignificant U-shaped relati onship, with the lowest risk occurring in normal-weight to overweight subje cts, whereas in severe COPD, mortality continued to decrease with increasin g BMI (test for trend: p < 0.001). Similar results were found for COPD-rela ted deaths, with the strongest associations found in severe COPD (RR for lo w versus high BMI: 7.11 [95% CI: 2.97 to 17.05]). We conclude that low BMI is an independent risk factor for mortality in subjects with COPD, and that the association is strongest in subjects with severe COPD.