Influence of long-term cigarette smoking on immunoglobulin E-mediated allergy, pulmonary function, and high-resolution computed tomography lung densitometry in elderly patients with asthma

Background: Smoking is the most important cause of chronic obstructive pulmonary disease (COPD). However, the influence of cigarette smoking on the pathogenesis of asthma in the elderly remains controversial. This study attempted to clarify the influence of cigarette smoking on elderly asthmatics. Methods: Forty-eight asthmatics over 70 years old (25 ex-smokers and 23 never-smokers) and 20 patients with COPD over 70 years old (all ex-smokers) were studied to determine the influence of cigarette smoking on IgE-mediated allergy (total IgE, IgE antibodies against inhalant allergens, bronchial hyper-responsiveness (BHR), generation of leukotriene (LT) B₄ and C₄), pulmonary function, and the relative area of lung showing attenuation values less than - 950 Hounsfield units (RA₉₅₀) on high-resolution computed tomography scans. Results: The incidence of positive IgE antibodies against inhalant allergens, BHR, and the generation of leukotriene B₄ (LTB₄) by leucocytes were significantly increased in patients with a history of smoking compared with those without. Residual volume (%RV) was significantly increased, and diffusing capacity for carbon monoxide was significantly decreased in ex-smokers with asthma and COPD compared with never-smokers with asthma. Inspiratory RA₉₅₀ and ratio of expiratory RA₉₅₀ to inspiratory RA₉₅₀ were significantly larger in asthmatics with a smoking history than in those without, and in COPD patients than in asthmatics. Conclusion: Cigarette smoking enhances the production of IgE antibodies, BHR, and generation of LTB ₄ by leucocytes in elderly asthmatics. Increased hyper-inflation or emphysematous changes of the lungs expressed by increased RA₉₅₀, closely related to %RV, was more frequently observed in exsmokers compared with never-smokers.