Statin use and risk of community acquired pneumonia in older people: population based case-control study

Abstract

Objective: To test the hypothesis that hydroxymethyl glutaryl coenzyme A reductase inhibitors (statins) may decrease the risk of community acquired pneumonia.

Design: Population based case-control study.

Setting: Group Health, a large integrated healthcare delivery system. Population Immunocompetent, community dwelling Group Health members aged 65 to 94; two matched controls for each case with pneumonia. Information on comorbid illnesses and functional and cognitive status, potential confounders of the association between statin use and risk of pneumonia, came from medical record review and computerised pharmacy data.

Main outcome measure: Adjusted estimates of risk of pneumonia in relation to current statin use.

Results: 1125 validated cases of pneumonia and 2235 matched controls were identified. Compared with controls, cases were more likely to have chronic lung and heart disease, especially severe disease, and functional or cognitive impairment. Current statin use was present in 16.1% (181/1125) of cases and 14.6% (327/2235) of controls (adjusted odds ratio 1.26, 95% confidence interval 1.01 to 1.56). Among cases admitted to hospital and matched controls, current statin use was present in 17.2% (68/395) of cases and 14.2% (112/788) of controls (adjusted odds ratio 1.61, 1.08 to 2.39, compared with non-use). In people in whom statins were indicated for secondary prevention, the adjusted odds ratio for risk of pneumonia in relation to current statin use was 1.25 (0.94 to 1.67); in those with no such indication, it was 0.81 (0.46 to 1.42).

Conclusions: Statin use was not associated with decreased risk of pneumonia among immunocompetent, community dwelling older people. Findings of previous studies may reflect "healthy user" bias.

Fig 1 Selection of cases and controls for inclusion in study

Fig 2 Risk estimates for association between statin use and community acquired pneumonia: sensitivity analyses. Current statin use defined as at least two prescriptions for statin within 180 days before index date; pneumonia outcomes defined from ICD-9 codes for cohort analyses and validated by medical record review for all other analyses. NA=not applicable. *Adjusted for matching variables, history of chronic obstructive pulmonary disease (with or without hospital admission), and other heart disease. †Possible statin use defined as receipt of at least one prescription for statin in previous year but not meeting criteria for current use; possible users removed from non-user (referent) group but included in model as separate category. ‡Indication for statin for secondary prevention defined as presence of at least one of congestive heart failure, stroke, diabetes, history of myocardial infarction or coronary revascularisation, or other heart disease. §On basis of days’ supply of most recent filled prescription. ¶All restrictions and adjustments based on administrative and pharmacy data