Active cigarette smoking and asthma

IntroductionActive cigarette smoking is common in adult asthmaticpatients and prevalence rates are similar to the generalpopulation. Current smoking rates among asthmatic patientsrange from 17% to 35% [1–7]. The highest rates are found inadults presenting to hospital emergency departments withacute asthma [3]. An additional number of adult asthmaticsare former smokers with prevalence rates ranging from 22%to 43% [1, 2]. The large subgroup of adult asthmatics who arecigarette smokers has been excluded from many studiespresumably because investigators were concerned thatpatients with smoking-related chronic obstructive pulmonarydisease (COPD) might be included in the study population.Thus, there is relatively little published information on theinuence of current cigarette smoking on asthma morbidity,therapeutic response to asthma medications and mechanismsof disease. In this edition of the journal, Sunyer et al. [8]examined the effects of asthma on peripheral cell bloodcounts among smokers and non-smokers and their resultssuggest that smoking modies the immunological response inasthma. In this editorial we will assess this new data in thelight of what is known about the clinical and immunologicaleffects of active smoking in adults with asthma (Fig. 1).Clinical effects of active smokingThe morbidity and mortality from asthma are increased inindividuals who are cigarette smokers [1–5, 9–12]. Currentasthmatic smokers have more severe asthma symptoms [1, 2]and worse indices of health status when compared with neversmokers [4]. Cigarette smoking and asthma combine toaccelerate the decline in lung function to a greater degree thaneither factor alone [7, 13]. Current smoking is associated withless appropriate management of asthma exacerbations,increasedhospital-based care forasthmaandmore emergencydepartment visits [3, 4, 10, 11]. The 6-year mortality rates arehigher for smokers than non-smokers following a near-fatalasthma attack, with an age adjusted odd ratio of 3.6 [12],although there is conicting evidence as to whether currentsmoking is a risk factor for near fatal asthma [5, 9].Therapeutic response to corticosteroidsCorticosteroids are the most effective anti-inammatorytherapy for chronic asthma. Both national and internationalasthma guidelines emphasize the importance of the earlyintroduction of inhaled corticosteroidsas rst-linetherapy forthose with mild disease [14, 15]. The evidence for theserecommendations is based on clinical trials that have beenundertaken largely in asthmatic patients who are neversmokers or former smokers. Until recently there was littleinformation about the effect of active smoking on corticos-teroid therapy in asthma. Active cigarette smoking impairsthe efcacy of short-term inhaled corticosteroid treatment insteroid-nai¨ve asthmatic patients [16]. In this randomizedplacebo-controlled study, the effect of treatment with inhaleduticasone propionate, 1000mg daily, or placebo for 3 weekswas studied in steroid-nai¨ve adult asthmatic patients. Non-smokers had a signicant increase in mean morning peakexpiratory ow (PEF), mean forced expiratory volume in 1s(FEV