Smoking and Obesity Increase Airway Hyperesponsiveness Risk In the Elderly

Objective of our study was assessing whether smoking and obesity might affect airways hyperresponsiveness (AHR) differently in younger and older subjects and whether this influence might be due to their different impacts on baseline lung function values at different ages. Methods 3,903 consecutive adult subjects with normal lung function (1,920 males; mean age 35.1±16.2; median FEV1:97.3% of predicted [interquartile range (IQR):89.7-105.2] and FEV1/FVC:84.6% of predicted [IQR:79.8-89.2]), having performed a methacholine test, were considered. They were subdivided into three groups according to age (18-39, 40-64 and ≥65 years) and into different sub-groups according to body mass index (BMI) and smoking habits, considering two AHR level cut-offs (PD20≤1600 µg and PD20≤800 µg). Results PD20 was significantly lower (p<0.004) in obese subjects aged 18-39 years, in comparison to older patients. Smoking was an AHR risk factor for subjects aged 40-64 and especially for those aged >65 (OR:12.786 [IQR:1.450-112.753];p<0.0001). Obesity caused an AHR risk only in older subjects (>65 years) (OR:3.120 [IQR:1.144-8.509];p<0.0001). FEV1/FVC and FEF25-75% decreased progressively (p<0.001) with age in subjects with different weights/smoking habits. No reductions with age were observed in FEV1% and FVC% except for a significant FVC% decrease in older smokers compared to older non-smokers. Conclusion Smoking determined a progressively increasing AHR risk reaching its peak in the elderly. In younger obese individuals, AHR was higher than in obese elderly, whereas obesity was a higher AHR risk factor only in subjects aged >65 years. A small airway age-related reduction may cause the increased smoking/obesity induced AHR risk in older people