A Cochrane review [Abstract] 1 included 2 studies with a total of 26 340 subjects at risk of Alzheimer's disease (AD) and dementia. Pravastatin trial included 5804 patients aged 70-82 years and simvastatin trial 20 536 patients with 5806 patients at least 70 years old at study entry. Mean follow-up was 3.2 years in pravastatin and 5 years in simvastatin trial. In simvastatin trial mean total cholesterol was 5.9 mmol/l and LDL cholesterol (LDL) 3.4mmol/l at study entry with mean reduction in LDL of 1.0mmol/l in simvastatin group compared to placebo. In pravastatin trial mean total cholesterol was 5.7mmol/l and LDL 3.8 mmol/l at study entry with mean reduction in LDL of 1.02 mmol/l in pravastatin group compared to placebo. There was no difference in incidence of dementia in simvastatin trial (31 cases in both groups) nor in performance on the modified Telephone Interview for Cognitive Status at final follow-up (cognitive impairment ~24% in both groups). There was no difference in cognition between groups either in relation to age at study entry or previous history of cerebrovascular disease. In pravastatin trial cognitive function declined also at the same rate in both treatment groups, there was no significant difference in performance on letter digit codes, picture word learning test, Stroop and Mini Mental State Examination. There was no evidence that statins were detrimental to cognition, either.
Comment: The quality of evidence is downgraded by indirectness of evidence (differences between the outcomes of interest)
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