Association between obesity and lung function changes by sex and age in adults with asthma

Objective The lung function changes presenting before and after asthma treatment in obese people remain largely unknown. This study aimed to investigate the association between obesity and lung function changes before and after treatment in adults with asthma. Methods We enrolled 937 newly diagnosed asthma patients from Cohort for Reality and Evolution of Adult Asthma in Korea cohort in 2015-2017, who performed follow-up spirometry after three months of asthma treatment. The percentage changes (Delta) between the spirometry results before and after treatment were calculated. Patients were categorized into four body mass index (BMI) groups; underweight (<18.5), normal (18.5-22.9), overweight (23.0-24.9), and obese (>= 25.0). Association between percent change of pulmonary function and BMI was analyzed according to sex and/or age (< 45 yrs, 45-65 yrs, >= 65 yrs), which were statistically corrected for age, sex, smoking status, and medication history. Results There was no consistent correlation between BMI and each lung function parameter. However, there were significant differences between BMI and Delta FEV1/FVC before and after 3 months of controller treatment. The obese asthmatics showed significantly lower Delta FEV1/FVC (6.0 +/- 13.5%) than the underweight (12.6 +/- 21.4%, P = 0.044) or normal weight (9.1 +/- 14.6%, P = 0.031). Middle-aged women had higher BMI (24.11 +/- 3.60 vs. 22.39 +/- 3.52) and lower Delta FEV1/FVC (5.7 +/- 11.9% vs. 8.9 +/- 14.3%, P = 0.012) than young women. Conclusions Obesity is negatively correlated with the Delta FEV1/FVC before and after controller treatment. Sex and age differentially contribute to lung function changes in response to asthma medications in adult asthmatics, showing a significant decrease in the Delta FEV1/FVC in middle-aged women.