title: Statins and associated risk of pneumonia: a systematic review and meta-analysis of observational studies.
abstract: OBJECTIVE
  Statins have potential anti-inflammatory effects, but the association between statin use and lower incidence of pneumonia is unclear. We have therefore performed a systematic review on the risk of pneumonia in statin users versus non-users.
  
  
  METHODS
  MEDLINE and EMBASE were searched in December 2010 for controlled observational studies that reported on the risk of pneumonia in statin users. We performed a random effects meta-analysis and assessed heterogeneity using the I² statistic.
  
  
  RESULTS
  A total of 451 citations were screened, and ultimately nine studies (4 case-control, 4 retrospective cohort, 1 prospective cohort) with more than 3 million participants were included in the meta-analysis. Pooled analysis of seven studies that reported unadjusted data failed to show a significantly reduced risk of pneumonia [odds ratio (OR) 0.94, 95% confidence interval (CI) 0.84-1.06, p = 0.33, I² = 79%] in statin users as compared to non-users. However, a significant reduction in the likelihood of pneumonia associated with statin use (n = 8 studies, OR 0.85, 95% CI 0.75-0.97, p = 0.02, I² = 81%) was found in the meta-analysis of adjusted data. Both analyses were limited by substantial statistical heterogeneity. Sensitivity analysis failed to fully clarify the source of heterogeneity, but cohort studies seemed to be less heterogenous (n = 5 studies, OR 0.92, 95% CI 0.84-1.01, I² = 43%).
  
  
  CONCLUSIONS
  Our findings indicate that the purported benefit of statins in preventing pneumonia is inconsistent, and of low magnitude, with upper bounds of the confidence interval being close to null. In view of the substantial statistical and clinical heterogeneity in the dataset, there is no convincing evidence to support the therapeutic application of statins for reducing the risk of pneumonia.
authors.affiliation: School of Medicine, University of East Anglia, Norwich, NR4 7TJ, UK.
authors.forename: Chun Shing
authors.initials: CS
authors.lastname: Kwok
authors.forename: Jessica Ka-Yan
authors.initials: JK
authors.lastname: Yeong
authors.forename: Richard M
authors.initials: RM
authors.lastname: Turner
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Cavallazzi
authors.forename: Sonal
authors.initials: S
authors.lastname: Singh
authors.forename: Yoon Kong
authors.initials: YK
authors.lastname: Loke
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use*; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000627:therapeutic use*; D011014:Pneumonia / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control*; D012307:Risk Factors
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors
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