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Low Childhood IQ Tied to Dementia in Old Age
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WEDNESDAY, June 25 — Your IQ in childhood may predict your odds of getting a common form of dementia in old age, according to Scottish researchers who turned to 76-year-old test scores to come to that conclusion.
"This study draws on unique childhood IQ data and finds that lower childhood IQ increases risk of vascular dementia, but not the most common cause of dementia, Alzheimer's disease," said study co-author John M. Starr, a professor of health and aging at the University of Edinburgh in Scotland.
The finding was published in the June 25 online issue of Neurology.
Vascular dementia is the second most common form of dementia, after Alzheimer's disease, the researchers noted. It occurs when the blood supply to brain cells is impaired, often by chronic problems such as high blood pressure or diabetes.
To explore the origins of dementia generally, the authors looked at the school records of 173 Scottish men and women, all of who were born in 1921. Each had participated in a standardized survey of mental health and ability conducted in 1932, when the children were about 11 years old.
All the patients had been diagnosed with some form of dementia at some point after the age of 65. Almost half of the dementia cases were classified as Alzheimer's disease. Almost 19 percent were diagnosed with vascular dementia, while close to 5 percent were a mix of the two.
Childhood test results among the dementia patients were compared with results for two additional groups of healthy patients of similar ages, genders, birth locations, and parental occupations.
Patients with vascular dementia had significantly lower scores in terms of mental ability than the healthy patient groups, the researchers reported. Having a higher test score at age 11 was associated with a significantly lower risk for vascular dementia, they noted. No such trends emerged for Alzheimer's disease.
Vascular disease stresses the brain and raises the risk for dementia, Starr said. So, the finding could help experts reassess their approach to preventing dementia, he believes.
To date, physicians have typically faced two options, he noted. They can either help the brain resist stress by focusing on the patient's "cognitive reserve" — thought to be made up of factors such high IQ and good education. Or they can simply try to reduce the amount of vascular stress the brain faces.
Because a lower IQ had no impact on Alzheimer's disease risk, the latter strategy — reducing vascular stressors on the brain — may be the better option, Starr said. That means cutting down on vascular risk factors such as smoking, high blood pressure, and high cholesterol.
However, Dr. Charles DeCarli, a professor of neurology and director of the Alzheimer's Disease Center at the University of California at Davis in Sacramento, said he isn't convinced of a link between IQ and vascular dementia.
"This is an interesting study and an interesting take," he said. "And, of course, I agree that it is always important and useful, as a general public health measure, to address the risk factors for vascular dementia."
"But I don't think you arrive at any conclusions about these kind of risk associations with dementia without first looking at these patient's brains," DeCarli added. "And they haven't. This would be important, because, on the one hand, much of the risk for various kinds of dementia is inherited. And, on the other, Alzheimer's typically strikes at an older age than vascular dementia. So, while you may see vascular dementia develop at an earlier point in time, it doesn't mean that the risk for Alzheimer's isn't there down the road. So, I think these conclusions are premature."
SOURCES: John M. Starr, FRCPEd, professor of health and aging, University of Edinburgh, Scotland; Charles DeCarli, M.D., professor, neurology, and director, Alzheimer's Disease Center, University of California at Davis, Sacramento; June 25, 2008, Neurology
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