The role of HMG-CoA reductase inhibitors, or statins, in cardiovascular protection is well established.
However, evidence in the current literature is conflicting as to the effect of statins on cognitive function.
It has been postulated that statins may prevent dementia of the Alzheimer's type through inhibition of beta-amyloid formation and thus decreased production of neurofibrillary tangles and plaques.
Other studies have suggested that statins can contribute to memory loss.

The proposed mechanism relates to cholesterol's essential role in myelin production.
Statins, especially the more lipophilic ones ( e.g., Atorvastatin and Simvastatin ), may cross the blood-brain barrier and decrease the amount of central nervous system ( CNS ) cholesterol necessary for the formation of myelin.

Inadequate myelin production may result in demyelination of nerve fibres in the CNS and thus lead to memory loss.
Memory impairment is listed in the product monograph for Pravachol.

From the date of marketing of statins in Canada to May 31, 2005, Health Canada received 19 reports of amnesia suspected of being associated with these drugs.
The onset was reported to occur within 1 month after starting statin therapy in 5 cases, within 1 year in 7 cases and after 1 year in 3 cases. Four cases did not report an onset date.
Eleven reports described that the amnesia resolved or improved when the drug was discontinued or the dose reduced, and one of them also described a positive rechallenge. Other reports did not provide this information.

Given these findings, changes in cognitive status temporally associated with statin therapy should be monitored.

Source: Health Canada, 2005


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