Smoking and New-Onset Asthma in a Prospective Study on Italian Adults

Abstract

Background: The existence of a cause-effect relation between active smoking and new-onset asthma in adults, although supported by several studies, has not been proven yet. Aims: We aimed to prospectively study asthma incidence as a function of smoking habits in the Italian adult population. Methods: A population-based cohort of 5,241 non-asthmatics was enrolled in Verona and Sassari in 1998-2000. The cohort was contacted again in 2007-2009 within the Gene-Environment Interactions in Respiratory Diseases study, and 3,187 subjects (60.8%) answered a screening questionnaire on smoking habits and respiratory disorders. The relation between smoking habits and self-reported new-onset asthma, defined as asthma attacks/use of medicines for asthma, was investigated by a multivariable logistic model. Results: During follow-up, 145 new cases of asthma were observed, yielding a cumulative incidence of 4.6% (95% CI 3.9-5.4); cumulative incidence of asthma did not significantly differ among never-smokers (76/1,666 = 4.6%), ex-smokers (30/554 = 5.4%) and current smokers (39/883 = 4.4%) (p = 0.641). In a multivariable analysis, the most important risk factor for asthma onset was allergic rhinitis (OR = 4.00, 95% CI 3.68-4.35). Compared to never-smokers, the risk of asthma onset was slightly increased in ex-smokers (OR = 1.28, 1.09-1.49) but not in current smokers (OR 1.01, 0.66-1.53). Current smoking became a significant predictor only when both new-onset wheezing and new-onset asthma were considered as the outcome (OR = 2.03, 1.35-3.05). Conclusions: In this prospective study, current smoking was not a risk factor for new-onset asthma, unless new-onset wheezing was also considered. The increase in asthma incidence among ex-smokers was likely due to reverse causation.

Global, regional, and national deaths, prevalence, disability-adjusted life years, and years lived with disability for chronic obstructive pulmonary disease and asthma, 1990–2015: a systematic analysis for the Global Burden of Disease Study 2015

“…We estimate only a small proportion of asthma burden due to risks quantified in GBD: 10·1% from occupational asthmagens and 7·8% due to smoking. 59 , 60 Evidence from long-term observational studies and birth cohorts have rendered three hypotheses on other causes and triggers of asthma, namely the hygiene, westernisation, and obesity or sedentarism hypotheses. Comparative studies 61 , 62 of rural and urban populations gave rise to the hygiene theory that exposure to infections in early childhood explains the lower prevalence of asthma in rural areas.…”

Inhalant Allergens in Portugal

“…In general, asthma and allergic rhinitis are more common in young people, yet their prevalence in the elderly is increasing [110] . Asthma is a chronic inflammatory disease of the airways characterized by recurrent episodes of wheezing, chest tightness, and breathlessness [111] . In turn, allergic rhinitis is a disorder of the upper airways resulting from IgE-mediated inflammation of the nose upon contact of the nasal mucosa with allergens.…”

Environmental Causes of Asthma

“…Although there are contradictory data, 79,80 many articles suggest that smoking is either not a risk factor or only a minor risk factor for the development of asthma. [81][82][83] Smoking does, however, appear to make asthma more severe. 78,84 It is difficult to convincingly sort out, but we believe smoking asthmatics probably have a greater risk of developing COPD compared with smoking nonasthmatics.…”