In patients with chronic obstructive pulmonary disease (COPD), decreased body mass index (BMI) is a significant risk factor for an accelerated decline in lung function in men but not in women. Researchers conducted a pooled analysis that included patient-level data from 6 randomized controlled trials and 1 noninterventional prospective study, and the results were published in the journal Respiratory Research.
The researchers pooled individual-level data from 7 large international studies into a single, combined dataset. They sought to examine the dose-response relationship between BMI and rate of decline in forced expiratory volume in 1 second (FEV1) in patients with mild and moderate COPD, based on gender and smoking status.
The pooled data in the current study included a total of 8686 patients with COPD from 7 studies, with a median duration of 36 months of follow-up. The mean baseline participant age was 51.9 years. Overall, 37% of the patients were women and 56% were current smokers. The patients who were evaluated had Global Initiative for Chronic Obstructive Lung Disease (GOLD) grade 1 (mild) or grade 2 (moderate) disease.
The primary study outcome was change in the absolute value of postbronchodilator FEV1 over time. The primary exposure — BMI at baseline visit — was obtained by dividing a participant’s weight (expressed in kg) by height squared (m2). The effects of gender on BMI values were assessed as well, controlling for the confounding effect of cigarette smoking on the findings.
Results of the study showed that gender significantly altered the association between BMI and decline in FEV1 (P <.001). Among men, the dose-response curve revealed a reverse relationship between BMI and rate of decline in FEV1 values. In fact, a rise in BMI of 1 kg/m2 reduced FEV1 decline by approximately 1.05 mL per year (95% CI, 0.96-1.14). In contrast, in women, BMI had a very small, clinically insignificant effect, with a rise in BMI of 1 kg/m2 associated with a decreased decline in FEV1 by only 0.16 mL per year (95% CI, 0.11-0.21). The gender-modified relationships were similar in GOLD 1 and GOLD 2 participants, as well as in current smokers and former smokers.
The investigators concluded that the findings from the current study show that underweight male smokers with GOLD 1 COPD are at the highest risk for rapid progression of disease, and should therefore be monitored closely and be robustly counseled for smoking cessation. Since BMI is an approximate measurement of nutritional status, which is unable to differentiate between fat and fat-free mass or its distribution, future studies need to consider other anthropometric measurements in female patients with mild to moderate COPD as well as the potential role of muscle and fat mass in gender-specific progression of disease.
Chen W, Sadatsafavi M, FitzGerald JM, Lynd LD, Sin DD. Gender modifies the effect of body mass index on lung function decline in mild-to-moderate COPD patients: a pooled analysis. Respir Res. 2021;22(1):59. doi:10.1186/s12931-021-01656-5