Body mass index and fat free mass index in obstructive lung disease in Korea

OBJECTIVE: To investigate the relationship between body mass index (BMI), fat free mass index (FFMI) and obstructive lung disease in Korea.

DESIGN: Based on a large population-based, nationwide survey conducted in Korea, 822 subjects with airway obstruction and the same number of healthy control subjects were selected. Spirometry and dual-energy X-ray absorptiometry were used for analysis.

RESULTS: Subjects with airway obstruction had a lower mean BMI and FFMI than the control group (23.6 vs. 23.9 kg/m² for BMI, P = 0.015 and 17.2 vs. 17.5 kg/m² for FFMI, P = 0.013); the BMI (P < 0.001) and FFMI (P < 0.001) values decreased significantly in subjects with severe airway obstruction. The proportion of subjects who were underweight or who had a low FFMI 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 one-second forced expiratory volume (FEV₁; P = 0.001) and FEV₁/forced vital capacity values (P < 0.001).

CONCLUSION: We suggest that lower BMI and FFMI are associated with degree of airway obstruction and that the assessment of BMI and body composition is necessary in patients with severe airway obstruction.