CRD Summary: The authors concluded that statin therapy significantly reduced the risk of developing all cerebrovascular events and ischaemic stroke, but was associated with a non-significant increased risk of haemorrhagic stroke. Overall, this review appeared to be well conducted, but it was difficult to assess the reliability of the findings without further information about the quality of the studies.

CRD Commentary: The review addressed a clear question and was supported by clear inclusion criteria. Attempts to identify all relevant studies were undertaken by searching electronic databases and other sources, including conference abstracts. The authors did not find any publication bias. As the search was limited to English-language publications, language bias may have been introduced. Some quality assessment criteria were assessed, but were not adequately reported. Although the overall sample sizes were large, sensitivity analyses of better-quality studies would have provided more confidence in the summary results. Three reviewers were involved in some aspects of the review process, which reduced the risk of reviewer bias. The studies were appropriately summarised in a meta-analysis, but the authors did not discuss potential sources of statistical heterogeneity in one of the analyses. Overall, this review appeared to be well-conducted, but it was difficult to assess the reliability of the findings without further information about the quality of the studies.