Multiple strokes and the complications and characteristics of the stroke itself are more important predictors of post-stroke dementia than are underlying vascular risk factors. As such, providing the best possible stroke care and secondary prevention measures could reduce the burden of dementia. These are the conclusions of an Article published Online First and in the November edition of the Lancet Neurology.
Although it is widely accepted that stroke is associated with an increased risk of subsequent dementia, studies show conflicting results on the risk factors for and prevalence of pre-stroke and post-stroke dementia. Reliable data on the risks and predictors of post-stroke dementia are needed to inform patients and carers, plan clinical services and trials, and establish the overall burden of stroke, and to understand better the causes of post-stroke dementia.
To provide more evidence, Sarah Pendlebury and Peter Rothwell from the Stroke Prevention Research Unit in Oxford, UK, conducted a systematic review of studies published between 1950 and May 1, 2009, to assess the conflicting prevalence data and to identify the risk factors for pre-stroke and post-stroke dementia. In total, 22 hospital-based and 8 population-based studies involving 7511 patients in 73 articles were examined.
Overall, findings showed that post-stroke dementia rates in the first year after stroke were highly varied, with rates ranging from 7.4% in population-based studies in which pre-stroke dementia was excluded to 41.3% in hospital-based studies of patients with recurrent stroke in which pre-stroke dementia was included. However, 93% of the variance in these rates could be explained by differences in factors such as study setting (hospital vs population based) and case mix (whether patients with pre-stroke dementia or first ever or recurrent stroke were included or not).
Importantly, the authors found that the risk of dementia was associated with the occurrence of strokes and the number of strokes rather than with underlying vascular risk factors. Indeed, dementia rates were about three times as high after recurrent stroke than after first stroke. About 10% of patients developed dementia within the first few months of a first stroke and 30% of patients developed dementia after a recurrent stroke.
Findings also showed that the characteristics and complications of the stroke were closely related to post-stroke dementia and emphasised the importance of the stroke itself rather than underlying vascular risk factors in the causes of post-stroke dementia. By contrast, significant predictors of pre-stroke dementia were found to be similar to those for Alzheimer's dementia and included factors such as female sex, a family history of stroke, and medial temporal lobe atrophy.
The authors conclude: "Optimum acute stroke care and secondary prevention of stroke are likely to be effective for reducing the burden of post-stroke dementia. Further studies are needed to identify the independent predictive factors, [and] to develop a risk factor score for use in clinical practice and trials."
In an accompanying Reflection and Reaction, Michael Hennerici from the University of Heidelberg, Germany, discusses the mechanisms involved in post-stroke dementia and suggests that the systematic treatment of high blood pressure is the best strategy for preventing both stroke and dementia in ageing people.
Sarah Pendlebury, Stroke Prevention Research Unit, Oxford, UK. T) +44 (0)1865 231 606 or +44 (0)7876 502 710 (mobile) E) sarah.pendlebury@clneuro.ox.ac.uk
Dr M G Hennerici, University of Heidelberg, Mannheim, Germany. T) +49 621 383 2885 E) Hennerici@neuro.ma.uni-heidelberg.de
For full Article and Reflection and Reaction, see: http://press.thelancet.com/tlnprestroke.pdf
Journal
The Lancet Neurology