BACKGROUND: Increased risk of acute exacerbation of chronic obstructive pulmonary disease (COPD) has been reported in patients who are overweight and obese. However, the effects of body fat in patients with normal or low body mass index (BMI) and COPD remain unknown. This study aimed to examine the association between acute exacerbations of COPD and the lean-to-fat (LTF) ratio in patients with a normal or low BMI.

MATERIAL AND METHODS: Patients with COPD (n=68) underwent assessment of body composition, in whom 43 cases had a normal BMI (18.5 to 25 kg/m²) and 14 cases were underweight (<18.5 kg/m²). Patients with COPD were treated according to current clinical guidelines and underwent regular follow-up for one year. Acute exacerbations of COPD were recorded.

RESULTS: BMI, the fat-free mass index (FFMI), skeletal muscle mass index (SMMI), and LTF ratio had no significant effect of the risk of acute exacerbations of COPD in the whole study cohort, but a low LTF ratio was significantly associated with reduced risk of acute exacerbations of COPD in the subgroup with a BMI<25 kg/m² (OR=4.528; P<0.05). The Fat Mass Index (FMI) had a protective effect in the whole cohort (OR=0.292; P=0.024) and in the subgroup with BMI <25 kg/m² (OR=0.253, P=0.049). The cumulative incidence of acute exacerbations of COPD was significantly increased in the patients with a high LTF ratio in the whole cohort (P=0.047) and in the subgroup with BMI <25 kg/m² (P=0.014).

CONCLUSIONS: In patients with BMI <25 kg/m², the LTF ratio was positively correlated with the risk of occurrence of acute exacerbations of COPD.

Keywords: Body Composition, Disease Progression, Pulmonary Disease, Chronic Obstructive, Adipose Tissue, Aged, 80 and over, Body Mass Index, Cohort Studies, Lung Diseases, Obesity, overweight, Patients, Risk Factors, Weight Loss