title: Smoking cessation and the risk of hospitalization for pneumonia.
abstract: BACKGROUND
  Smoking increases the risk of hospitalization for pneumonia, yet it is unknown if smoking cessation changes this risk. We sought to determine if smoking cessation and the duration of abstinence from tobacco reduce the risk of pneumonia hospitalization.
  
  
  METHODS
  We performed secondary analysis of data collected from male United States Veterans participating in a randomized trial. We used Cox proportional-hazard models to estimate risk of hospitalization for pneumonia within one year of enrollment. We adjusted for confounders, including: demographics, comorbidity, alcohol use, prior pneumonia, inhaled corticosteroid use, and intensity of tobacco exposure. Among a restricted cohort excluding never smokers, we assessed for effect modification by a diagnosis of chronic obstructive pulmonary disease (COPD).
  
  
  RESULTS
  Of the 25,235 participants, we identified 6720 current, 13,625 former, and 4890 never smokers. Compared to current smokers, never smokers had a decreased (adjusted HR 0.48, 95% CI 0.31-0.74), while former smokers had no difference in (adjusted HR 0.83, 95% CI 0.63-1.09) risk of hospitalization for pneumonia. Among participants without COPD, former smokers had a lower risk of hospitalization (adjusted HR 0.65, 95% CI 0.45-0.95). However, this lower risk was isolated to those who quit tobacco more than 10 years previously (adjusted HR 0.62, 95% CI 0.41-0.93). Among those with COPD, there was no difference in risk with smoking cessation or duration of remaining tobacco-free.
  
  
  CONCLUSIONS
  Tobacco cessation is likely important in reducing hospital admissions for pneumonia, but its benefit depends on duration of smoking cessation and is likely attenuated in the presence of COPD.
authors.affiliation: Health Services Research and Development (HSR&D) Northwest Center of Excellence, Department of Veterans Affairs Puget Sound Health Care System, Seattle, WA 98101, USA. lcecere@uw.edu
authors.forename: Laura M
authors.initials: LM
authors.lastname: Cecere
authors.forename: Emily C
authors.initials: EC
authors.lastname: Williams
authors.forename: Haili
authors.initials: H
authors.lastname: Sun
authors.forename: Chris L
authors.initials: CL
authors.lastname: Bryson
authors.forename: Brendan J
authors.initials: BJ
authors.lastname: Clark
authors.forename: Katharine A
authors.initials: KA
authors.lastname: Bradley
authors.forename: David H
authors.initials: DH
authors.lastname: Au
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D011014:Pneumonia / Q000453:epidemiology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D016540:Smoking Cessation / Q000706:statistics & numerical data*; D014481:United States / Q000453:epidemiology; D014728:Veterans