Higher Risk of Wheeze in Female than Male Smokers. Results from the Swedish GA2LEN Study

Anders Bjerg,Bo Lundbäck,Jan Lötvall,Karl A Franklin,Linda Ekerljung,Bertil Forsberg,Roelinde Middelveld,Jonas Eriksson,Kjell Larsson,Inga Sif Ólafsdóttir,Kjell Torén,Christer Janson,Sven-Erik Dahlén

doi:10.1371/journal.pone.0054137

Abstract

BackgroundWomen who smoke have higher risk of lung function impairment, COPD and lung cancer than smoking men. An influence of sex hormones has been demonstrated, but the mechanisms are unclear and the associations often subject to confounding. This was a study of wheeze in relation to smoking and sex with adjustment for important confounders.MethodsIn 2008 the Global Allergy and Asthma European Network (GA2LEN) questionnaire was mailed to 45.000 Swedes (age 16–75 years), and 26.851 (60%) participated. “Any wheeze”: any wheeze during the last 12 months. “Asthmatic wheeze”: wheeze with breathlessness apart from colds.ResultsAny wheeze and asthmatic wheeze was reported by 17.3% and 7.1% of women, vs. 15.8% and 6.1% of men (both p<0.001). Although smoking prevalence was similar in both sexes, men had greater cumulative exposure, 16.2 pack-years vs. 12.8 in women (p<0.001). Most other exposures and characteristics associated with wheeze were significantly overrepresented in men. Adjusted for these potential confounders and pack-years, current smoking was a stronger risk factor for any wheeze in women aged <53 years, adjusted odds ratio (aOR) 1.85 (1.56–2.19) vs. 1.60 (1.30–1.96) in men. Cumulative smoke exposure and current smoking each interacted significantly with female sex, aOR 1.02 per pack-year (p<0.01) and aOR 1.28 (p = 0.04) respectively. Female compared to male current smokers also had greater risk of asthmatic wheeze, aOR 1.53 vs. 1.03, interaction aOR 1.52 (p = 0.02). These interactions were not seen in age ≥53 years.DiscussionIn addition to the increased risk of COPD and lung cancer female, compared to male, smokers are at greater risk of significant wheezing symptoms in younger age. This became clearer after adjustment for important confounders including cumulative smoke exposure. Estrogen has previously been shown to increase the bioactivation of several compounds in tobacco smoke, which may enhance smoke-induced airway inflammation in fertile women.

Highlights

The detrimental effects of tobacco smoking on respiratory health are well known
The prevalence of respiratory symptoms common in asthma was higher in women compared to men, whereas chronic bronchitis was common in both sexes
Little is presently known about sex-specific effects of smoking on respiratory symptoms

Summary

Introduction

Most importantly, smoking significantly accelerates lung function decline, and increases the risk of lung cancer and chronic obstructive pulmonary disease (COPD) [1]. As measured by a single spirometry, does not necessarily correlate well with respiratory symptoms in the individual [7]. In COPD despite fixed airway obstruction being the hallmark of disease symptoms, general health status and exercise capacity all correlate poorly with lung function impairment [7,8]. Women who smoke have higher risk of lung function impairment, COPD and lung cancer than smoking men. An influence of sex hormones has been demonstrated, but the mechanisms are unclear and the associations often subject to confounding This was a study of wheeze in relation to smoking and sex with adjustment for important confounders

Methods

Results

Conclusion