title: Recurrent community-acquired pneumonia in patients starting acid-suppressing drugs.
abstract: BACKGROUND
  Several studies suggest that proton pump inhibitors (PPIs) and histamine 2-receptor antagonists (H2s) increase risk of community-acquired pneumonia. To test this hypothesis, we examined a prospective population-based cohort predisposed to pneumonia: elderly patients (> or =65 years) who had survived hospitalization for pneumonia.
  
  
  METHODS
  This study featured a nested case-control design where cases were patients hospitalized for recurrent pneumonia (> or =30 days after initial episode) and controls were age, sex, and incidence-density sampling matched but never had recurrent pneumonia. PPI/H2 exposure was classified as never, past, or current use before recurrent pneumonia. The association between PPI/H2s and pneumonia was assessed using multivariable conditional logistic regression.
  
  
  RESULTS
  During 5.4 years of follow-up, 248 recurrent pneumonia cases were matched with 2476 controls. Overall, 71 of 608 (12%) current PPI/H2 users had recurrent pneumonia, compared with 130 of 1487 (8%) nonusers (adjusted odds ratio [aOR] 1.5; 95% confidence interval [CI], 1.1-2.1). Stratifying the 608 current users according to timing of PPI/H2 initiation revealed incident current-users (initiated PPI/H2 after initial pneumonia hospitalization, n=303) bore the entire increased risk of recurrent community-acquired pneumonia (15% vs 8% among nonusers, aOR 2.1; 95% CI, 1.4-3.0). The 305 prevalent current-users (PPI/H2 exposure before and after initial community-acquired pneumonia hospitalization) were equally likely to develop recurrent pneumonia as nonusers (aOR 0.99; 95% CI, 0.63-1.57).
  
  
  CONCLUSIONS
  Acid-suppressing drug use substantially increased the likelihood of recurrent pneumonia in high-risk elderly patients. The association was confined to patients initiating PPI/H2s after hospital discharge. Our findings should be considered when deciding to prescribe these drugs in patients with a recent history of pneumonia.
authors.affiliation: Department of Public Health Sciences, School of Public Health, University of Alberta, Edmonton, Alberta, Canada. deurich@ualberta.ca
authors.forename: Dean T
authors.initials: DT
authors.lastname: Eurich
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Sadowski
authors.forename: Scot H
authors.initials: SH
authors.lastname: Simpson
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Marrie
authors.forename: Sumit R
authors.initials: SR
authors.lastname: Majumdar
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000416:Alberta / Q000453:epidemiology; D000897:Anti-Ulcer Agents / Q000009:adverse effects* / Q000627:therapeutic use; D016022:Case-Control Studies; D015331:Cohort Studies; D017714:Community-Acquired Infections / Q000453:epidemiology / Q000209:etiology / Q000628:therapy; D016001:Confidence Intervals; D004198:Disease Susceptibility / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011014:Pneumonia / Q000453:epidemiology* / Q000209:etiology / Q000628:therapy; D011336:Probability; D054328:Proton Pump Inhibitors / Q000009:adverse effects* / Q000627:therapeutic use; D012008:Recurrence; D012306:Risk; D012720:Severity of Illness Index; D017678:Sex Distribution; D015996:Survival Rate; D016896:Treatment Outcome
chemical_list: D000897:Anti-Ulcer Agents; D054328:Proton Pump Inhibitors