Statins reduce all-cause mortality in chronic obstructive pulmonary disease: a systematic review and meta-analysis of observational studies

BACKGROUND: Recent observational studies have suggested that use of statins reduces mortality in patients suffering from chronic obstructive pulmonary disease. However, no meta-analysis has reported the pooled hazard ratio of statins to all-cause mortality. METHODS: We searched for eligible articles using five databases. We included randomized controlled trials and cohort studies written in English using original data reporting the hazard ratio of statins to all-cause, cardiovascular-related, cancer-related, or respiratory-related mortality. A fixed model with the confidence interval method was used. Publication bias was evaluated by funnel plot and Begg’s test, and was corrected using Duval’s trim and fill method. Sensitivity analyses were also conducted. RESULTS: We included 10 out of 128 articles. The pooled hazard ratio of statins to all-cause mortality involving 16269 patients was 0.81 (95% CI: 0.75-0.86, P < 0.001) with moderate heterogeneity (I2 = 52%, P = 0.032). The sensitivity analysis and funnel plot suggested the existence of publication bias. After three possibly unpublished cohorts were imputed, the pooled hazard ratio of 0.83 (95% CI: 0.78-0.88, P < 0.001) still suggested a favorable prognosis in statin-treated patients. The pooled hazard ratio of statins to cardiovascular-related, cancer-related, and respiratory-related mortality were 0.52 (95% CI: 0.27-1.01, P = 0.052), 0.57 (95% CI: 0.32-1.01, P = 0.056), and 0.55 (95% CI: 0.43-0.78, P < 0.001), respectively, although these results were not conclusive as we could not find a sufficient number of original studies dealing with those forms of mortality. CONCLUSIONS: The use of statins for patients suffering from chronic obstructive pulmonary disease may reduce all-cause mortality. This conclusion should be re-evaluated by a registered large-scale randomized controlled trial.