Effects of body mass index on lung function in patients with chronic obstructive pulmonary disease / 中华健康管理学杂志

ABSTRACT

Objective:To investigate the effects of body mass index (BMI) on lung function in patients with chronic obstructive pulmonary disease (COPD).Methods:A total of 3 312 patients with COPD were selected from outpatients and inpatients in Department of Gerontal Respiratory Medicine of the First Hospital of Lanzhou University from August 2016 to August 2020, including 1 103 patients in stable period and 2 209 patients in acute exacerbation period. According to body mass index (BMI), these COPD patients were divided into four groups low weight (56 cases, 131 cases), normal weight (448 cases, 945 cases), overweight (424 cases, 773 cases) and obesity groups (175 cases, 360 cases) respectively in stable stage and in acute exacerbation stage. The lung function of inspiratory capacity (IC), vital capacity (VC), residual volume (RV)/total lung capacity (TLC), forced expiratory volume in 1 second (FEV 1), forced vital capacity (FVC), FEV 1/FVC, maximal mid-expiratory flow (MMEF), diffusing capacity of the lung for carbon monoxide (DLCO), DLCO normalized per liter alveolar volume (DLCO/VA), respiratory impedance (Zrs), respiratory resistance at 5 Hz (R5), respiratory resistance at 20 Hz (R20) and respiratory reactance at 5 Hz (X5) were measured using MasterScreen PFT in all patients, and the influence of BMI on lung function was analyzed respectively. The risk factors of impaired lung function were analyzed by ordered logistic regression with lung function grade as dependent variable and age, gender, smoking history, smoking index and BMI as independent variables (“%pred”represents the percentage of predicted value). Results:The proportion of patients with lung function grade Ⅲ/Ⅳ in acute exacerbation period (64.9%, 37%, 27.4%, 24.4%) was higher than that in stable stage (42.9%, 25.9%, 13.7%, 9.1%), while the proportion of patients with lung function grade Ⅰ in stable stage (21.4%, 34.2%, 38.2%, 40.0%) was higher than that in acute exacerbation period (7.6%, 20.0%, 25.4%, 22.8%) (all P<0.05). The IC%pred, VC%pred, FEV 1%pred, FVC%pred, FEV 1/FVC, MMEF%pred, DLCO%pred, DLCO/VA%pred and R20 in low weight group were significantly lower than other groups both in stable period and acute exacerbation period (all P<0.05). The RV/TLC was higher in low weight group than that of normal weight and overweight groups in both periods (all P<0.05). The IC%pred, FEV 1%pred, FEV 1/FVC, DLCO%pred, DLCO/VA%pred, R5 and R20 in overweight and obesity groups were higher than those of normal weight group (all P<0.05). The RV/TLC, FEV 1/FVC, DLCO%pred, DLCO/VA%pred, Zrs, R5 and R20 in obesity group were higher than those of overweight group (all P<0.05). The ordered logistic regression analysis showed that low weight was independent risk factor for impaired lung function of COPD both in stable period [ OR (95% CI) 2.316 (1.206-3.554)] and acute exacerbation period [ OR (95% CI) 2.457 (1.647-3.669)]. Conclusion:Lower BMI has an adverse effect on lung function, and it is an independent risk factor for impaired lung function in COPD patients.