Background Epidemiological data suggest that statins improve the clinical outcome of respiratory infections. We sought to examine whether statin therapy decreases the risk of active TB.
Methods We conducted a nested case-control study on data obtained from a national health insurance claims database between 1999 and 2011. The use of statins was classified as current, recent, past or chronic use. Three conditional logistic regression models were used to estimate the incidence rate ratios (RRs). The first assessed the effect of statin use without further adjustment; the second adjusted (individually) for 75 potential confounders; and the third adjusted for the Disease Risk Score (DRS).
Results A total of 8098 new TB cases and 809 800 control patients were examined. All four types of statin users showed a decreased risk of active TB. Chronic use (>90 days in a calendar year) of statins was associated with the lowest unadjusted risk of TB (RR 0.74; 95% CI 0.63 to 0.87). The protective effect of active TB remained after adjusting for individual confounders (RR 0.66; 95% CI 0.56 to 0.78) and after DRS adjustment (RR 0.62; 95% CI 0.53 to 0.72). The effect estimates obtained for chronic and current use of statins were very similar. We also found that the active TB protection increased with increasing length of statin prescription.
Conclusions We found that statin therapy was associated with a decreased risk of active TB, and the length of statin therapy affected the TB protection. Given the observational nature of this study, the protective effect against active TB must be confirmed in future randomised trials.