New-onset dementia among stroke patients appears to be most prevalent after two or more strokes, indicating that providing the best possible stroke care and secondary prevention measures could help reduce dementia in persons who have suffered this vascular event.

Both providers and patients need reliable information on the prevalence and predictors of pre- and post-stroke dementia, but the published data are conflicting. Investigators at the stroke prevention research unit at John Radcliffe Hospital, Oxford, England, sorted through the scientific literature to identify risk factors for these two types of dementia. A review of 73 reports of studies involving a total of 7,511 patients, revealed that:

  • 10% of patients had dementia before first stroke
  • 10% developed dementia soon after first stroke
  • Approximately 30% developed dementia after recurrent stroke

“Rates [of post-stroke dementia] were about three times as high overall after recurrent stroke compared with first-ever stroke and seemed to rise after each event,” researchers point out in their report, which was published online ahead of print September 24, 2009, in The Lancet Neurology. “The risk of dementia was closely related to the occurrence of stroke and to the number of strokes, rather than to background vascular risk factors….[T]he occurrence of a stroke had a substantial and immediate effect on the absolute rate of dementia that was over and above the risk from previous lifetime exposure to vascular risk factors.”

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Medial temporal lobe atrophy, female sex, and a family history of dementia emerged as the strongest risk factors for pre-stroke dementia.

The authors contend that although acute stroke complications have not been proven to cause post-stroke dementia, the observed relationship between the two highlights the potential importance of avoiding recurrences.