Differential Impact of Low Fat-Free Mass in People With COPD Based on BMI Classifications

Background Alterations in body composition, including a low fat-free mass index (FFMI), are common in patients with COPD and occur regardless of body weight. Research Question Is the impact of low FFMI on exercise capacity, health-related quality of life (HRQL), and systemic inflammation different among patients with COPD stratified in different BMI classifications? Study Design and Methods We analyzed baseline data of patients with COPD from the COPD and Systemic Consequences-Comorbidities Network (COSYCONET) cohort. Assessments included lung function, bioelectrical impedance analysis, 6-min walk distance (6MWD), HRQL, and inflammatory markers. Patients were stratified in underweight, normal weight (NW), preobese, and obese according to BMI and as presenting low, normal, or high FFMI using 25th and 75th percentiles of reference values. Linear mixed models were used to investigate the associations between fat-free mass (FFM) and fat mass with secondary outcomes in each BMI group. Results Two thousand one hundred thirty-seven patients with COPD (Global Initiative for Chronic Obstructive Lung Disease stages 1-4; 61% men; mean ± SD age, 65 ± 8 years; mean ± SD FEV1, 52.5 ± 18.8% predicted) were included. The proportions of patients in underweight, NW, preobese, and obese groups were 12.3%, 31.3%, 39.6%, and 16.8%, respectively. The frequency of low FFMI decreased from lower to higher BMI groups (underweight, 81%; NW, 53%; preobese, 42%; and obese, 39%). FFM was associated with the 6MWD in the underweight group, even when adjusting for a broad set of covariates (P < .05). HRQL was not associated with FFM after adjustment for lung function or dyspnea (P > .32). Fat mass was associated with higher systemic inflammation in the NW and preobese groups (P < .05). Interpretation In patients with COPD with lower weight, such as underweight patients, higher FFMI is associated independently with better exercise capacity. In contrast, in preobese and obese patients with COPD, a higher FFMI was not consistently associated with better outcomes. Alterations in body composition, including a low fat-free mass index (FFMI), are common in patients with COPD and occur regardless of body weight. Is the impact of low FFMI on exercise capacity, health-related quality of life (HRQL), and systemic inflammation different among patients with COPD stratified in different BMI classifications? We analyzed baseline data of patients with COPD from the COPD and Systemic Consequences-Comorbidities Network (COSYCONET) cohort. Assessments included lung function, bioelectrical impedance analysis, 6-min walk distance (6MWD), HRQL, and inflammatory markers. Patients were stratified in underweight, normal weight (NW), preobese, and obese according to BMI and as presenting low, normal, or high FFMI using 25th and 75th percentiles of reference values. Linear mixed models were used to investigate the associations between fat-free mass (FFM) and fat mass with secondary outcomes in each BMI group. Two thousand one hundred thirty-seven patients with COPD (Global Initiative for Chronic Obstructive Lung Disease stages 1-4; 61% men; mean ± SD age, 65 ± 8 years; mean ± SD FEV1, 52.5 ± 18.8% predicted) were included. The proportions of patients in underweight, NW, preobese, and obese groups were 12.3%, 31.3%, 39.6%, and 16.8%, respectively. The frequency of low FFMI decreased from lower to higher BMI groups (underweight, 81%; NW, 53%; preobese, 42%; and obese, 39%). FFM was associated with the 6MWD in the underweight group, even when adjusting for a broad set of covariates (P < .05). HRQL was not associated with FFM after adjustment for lung function or dyspnea (P > .32). Fat mass was associated with higher systemic inflammation in the NW and preobese groups (P < .05). In patients with COPD with lower weight, such as underweight patients, higher FFMI is associated independently with better exercise capacity. In contrast, in preobese and obese patients with COPD, a higher FFMI was not consistently associated with better outcomes. Looking Beyond BMI Classifications With Complementary Assessment of Body Composition in COPDCHESTVol. 163Issue 5PreviewCOPD represents the third leading cause of morbidity and death globally.1 COPD is characterized by persistent symptoms of dyspnea and extra-parenchymal comorbidities that include alterations in body composition (low muscle mass and increased adiposity), as a consequence of risk factors such as malnutrition, physical inactivity, and corticosteroid use.2 Body composition changes have been shown to be an important prognostic marker of death in several COPD studies.3,4 Thus, a better understanding of body composition alterations in COPD may provide further insight into daily function and help with risk stratification. Full-Text PDF