title: Smoking influences response to inhaled corticosteroids in patients with asthma: a meta-analysis.
abstract: OBJECTIVE
  To determine the effects of smoking on efficacy of inhaled corticosteroids in asthmatics.
  
  
  METHODS
  Prospective/retrospective, controlled studies published up to May 2012 in smokers versus non-smokers with asthma using inhaled corticosteroids (ICSs) were retrieved from PubMed, Highwire and Embase databases.
  
  
  METHODS
  The primary outcomes were pulmonary function parameters [FEV(1) (forced expiratory volume in 1 second), a.m. PEF (a.m. peak expiratory flow) and p.m. PEF (p.m. peak expiratory flow)]. Secondary outcomes included differential eosinophil counts in sputum and peripheral blood, asthma control questionnaire-5 (ACQ-5) and concomitant use of medication. Pooled SMDs (standardized mean differences) were estimated by using a random-effect model and a fixed-effect model based on between-study heterogeneity.
  
  
  RESULTS
  Of 242 studies identified, ten (N = 4070) met the inclusion criteria (seven of budesonide-based interventions, two of fluticasone and one unknown ICS trial). Both smokers and non-smokers were similar in age and baseline FEV(1). Smoking yielded considerably reduced mean change in FEV(1) [SMD = -0.197, 95% CI: (-0.327, -0.066), p = 0.003], morning PEF [SMD = -0.796, 95% CI: (-1.047, -0.545), p < 0.001], night-time PEF [SMD = -0.501, 95% CI: (-0.797, -0.204), p = 0.001] and post-treatment FEV(1) [SMD = -0.178, 95% CI: (-0.309, -0.046), p = 0.008] and increased use of concomitant medications [SMD = 0.537, 95% CI: (0.166, 0.908), p = 0.005] in smokers, but not non-smokers with asthma, although there was no statistical difference in allergy-related endpoints and asthma score (ACQ-5).
  
  
  CONCLUSIONS
  Smoking is associated with attenuated response to inhaled corticosteroids in asthmatics. This offers a rationale for persuasion of smoking cessation. Treatment outcomes might be improved by smoking cessation leading to improved lung function and ameliorated symptoms.
authors.affiliation: Department of Epidemiology, School of Public Health and Tropical Medicine, Southern Medical University, Guangzhou, China.
authors.forename: Xueyan
authors.initials: X
authors.lastname: Zheng
authors.forename: Weijie
authors.initials: W
authors.lastname: Guan
authors.forename: Jinping
authors.initials: J
authors.lastname: Zheng
authors.forename: Ping
authors.initials: P
authors.lastname: Ye
authors.forename: Shan
authors.initials: S
authors.lastname: Liu
authors.forename: Junhua
authors.initials: J
authors.lastname: Zhou
authors.forename: Yiquan
authors.initials: Y
authors.lastname: Xiong
authors.forename: Qionghua
authors.initials: Q
authors.lastname: Zhang
authors.forename: Qing
authors.initials: Q
authors.lastname: Chen
mesh_terms: D000280:Administration, Inhalation; D000305:Adrenal Cortex Hormones / Q000008:administration & dosage* / Q000627:therapeutic use; D001249:Asthma / Q000188:drug therapy* / Q000503:physiopathology; D006801:Humans; D012129:Respiratory Function Tests; D012907:Smoking
chemical_list: D000305:Adrenal Cortex Hormones