Genes, environment, and dementia.

Specific genetic and environmental risk factors appear to increase the risk of dementia, reported Timo E. Strandberg of the University of Helsinki and his associates.

Of 357 elderly subjects with cardiovascular disease living in the community, 58 were found to have cognitive impairment at baseline (Mini-Mental State Examination score of less than 24), the investigators said. In a multivariate analysis, adjusted for age and the presence of diabetes, subjects who combined seropositivity for Herpesviridae, presence of apolipoprotein E (APOE) [epsilon]4, and less than a high school education were at significantly increased risk of cognitive impairment (risk ratio 6.1).

To test whether there is another meaningful variation of the APOE gene besides [epsilon]4, a subcohort of 216 subjects with the APOE [epsilon]3 haplotype (-219G [epsilon]3), previously associated with Alzheimer's disease, was examined and found to also be at greater risk for cognitive impairment. That risk ratio was 8.8, according to the investigators (Neurobiol. Aging 2005;26:1001-4).

It is unclear whether the latter associations are "specific to Herpesviridae or just reflect nonspecific effects of infection," the investigators said. A treatment study aimed at preventing cognitive decline with antiherpes medication would shed more light on this issue, they said.