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

Why such different results? Perhaps because of the broad reach of the population on which the autopsy study was based, says Dr. Montine. Most studies looking at the structural changes on autopsy in brains of persons with dementia have focused on participants in Alzheimer's disease center studies or in populations limited to one gender, ethnic or professional group. Individuals in this study were part of the Group Health Cooperative, one of the oldest and largest managed care programs in the United States.

Members in the group who reach 65 with normal cognitive ability are eligible to volunteer for an Adult Changes in Thought (ACT) study, established by Dr. Eric Larson, director of Research at the Group Health Cooperative. ACT participants undergo cognitive, neurological and psychological tests every two years until their death.

Between 1994 and 2006, the period covered by this study, 3,400 men and women entered the ACT study. They were representative of the Seattle urban and suburban area: white, Asian, African American and Hispanic, with a range of educational and professional levels. During this 12-year period, some participants suffered cognitive impairment and dementia, while others did not. Roughly a third of all participants died, and autopsies were performed on the 221 who had given permission for this to be done.

With 55 percent of the risk for dementia attributable to Alzheimer's and Lewy Body Dementia, these findings underscore the therapeutic imperative for developing new pharmacologic and other means of preventing or delaying the onset of Alzheimer's and Lewy Body disease, says Dr. Montine. But the unexpected finding that a third of the risk for dementia is related to small vessel disease also provides an additional reason to control hypertension and diabetes: not only to protect cardiovascular and renal health but also to protect the health of the brain.