Body mass index and fat free mass index in adults with chronic obstructive pulmonary disease in Korea

Abstract

Background: Body mass index (BMI) and fat free mass index (FFMI) are known to decrease in patients with chronic obstructive pulmonary disease (COPD). In these patients, a low BMI and FFMI are associated with worsening lung function and poor prognosis. Limited data is available on the relationship between BMI, FFMI and COPD in Asian countries, where mean BMI is lower than in Western countries.Methods: We used the data in Korean National Health and Nutrition Survey (KNHANES) from the years 2008 to 2010. A total of 822 subjects with documented airway obstruction and the same number of control subjects matched for age, sex and smoking status were selected. Spirometry and dual energy X-ray absorptiometry (DXA) were used for analysis. Result: Subjects with COPD had a lower mean BMI and FFMI compared with the control group (23.6 vs. 23.9 kg/m2 for BMI and 17.2 vs. 17.5 kg/m2 for FFMI, p = 0.015 and p = 0.013, respectively). The BMI and FFMI values decreased significantly in subjects with severe airway obstruction (p < 0.001), while those subjects with mild to moderate airway obstruction had values equivalent to those of the control group. The proportion of subjects who were underweight (BMI < 18.5 kg/m2) or who had a low FFMI (FFMI < 5 percentile) was significantly higher in the severe airway obstruction group (p < 0.001). The decrease in FFMI was more prominent in the lower extremities, followed by the upper extremities and the trunk. Subjects who were underweight had significantly lower FEV1 and FEV1/FVC values when compared with others subjects (p < 0.001). Conclusion: BMI and FFMI are decreased in adults with severe airway obstruction. The decrease in FFMI deficit was more prominent in the lower extremities. We suggest that the assessment of BMI and body composition is necessary in patients with severe airway obstruction, and active rehabilitation has to be considered to preserve fat free mass in those patients.