1/3 of risk for dementia attributable to small vessel disease, autopsy study shows

Alzheimer's disease may be what most people fear as they grow older, but autopsy data from a long-range study of 3,400 men and women in the Seattle region found that the brains of a third of those who had become demented before death showed evidence of small vessel damage: the type of small, cumulative injury that can come from hypertension or diabetes.

Dr. Thomas Montine, University of Washington, presented the study results at Experimental Biology 2008 in San Diego on April 6. His presentation was part of the scientific program of the American Society for Biochemistry and Molecular Biology (ASBMB).

In the autopsied brains of people who had experienced cognitive decline and dementia, 45 percent of the risk for dementia was associated with pathologic changes of Alzheimer's disease. Another 10 percent of dementia risk was associated with Lewy bodies, neocortical structural changes that indicate a degenerative brain disease known as Lewy Body Dementia, believed by some clinicians to be a variant of Alzheimer's and/or Parkinson's disease. But a third of the risk for dementia (33 percent) was associated with damage to the brain from small vessel disease.

Dr. Montine and his colleagues believe that, and are now studying in more detail, this small vessel damage is the cumulative effect of multiple small strokes caused by hypertension and diabetes, strokes so small that the person experiences no sensation or problems until the cumulative effect reaches a tipping point. This may be good news, says Dr. Montine. At a time when prevention and treatment for Alzheimer's remain investigational, methods for preventing complications of hypertension and diabetes are currently available.

These findings are very different from both conventional wisdom and from those of most autopsy studies of brain aging and dementia, says Dr. Montine.