NEW YORK (Reuters Health) - Lower premorbid cognitive ability at age 11 is a risk factor for developing vascular dementia, but not Alzheimer disease, in old age, British researchers report in the June 25 online issue of Neurology.

Dr. John M. Starr and colleagues at the University of Edinburgh conducted a case-control study involving individuals born in 1921 who underwent cognitive ability testing with the Moray House Test, or MHT, (maximum score 76) in the Scottish Mental Survey of 1932.

The final analysis included 63 subjects diagnosed with Alzheimer disease and 31 diagnosed with vascular dementia by the year 2003, when they would have been 82 years old. Case subjects were each matched with two control subjects by age, sex, and birthplace (control group 1), and two controls additionally matched by father's occupation (control group 2).

Vascular dementia cases had significantly lower test scores (34.0) than control group 1 (41.4, p = 0.02) and control group 2 (40.9, p = 0.01). However, there was no significant difference for Alzheimer disease cases.

According to conditional logistic regression analysis, each 10-point increase in MHT score (0.7 standard deviations) was associated with an odds ratio of 0.62 for vascular dementia compared with control group 2.

"The data support the hypothesis that lower premorbid cognitive ability acts as a risk factor for dementia, through pathways of vascular risk rather than more generic cognitive reserve," Dr. Starr and his associates conclude. "These data favor vascular risk reduction as a priority." Identifying a risk factor present during childhood suggests that prevention strategies could be implemented from childhood onwards, they add.

Neurology 2008.

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