麻豆传媒

Children with low intelligence test scores are more likely to develop late-onset Alzheimer鈥檚 disease, a Scottish team has found.

However, the reason for the link is hotly disputed. Lawrence Whalley of Aberdeen University led the new study and speculates that smarter people are better at compensating for the effects of age-related brain deterioration.

He says Alzheimer鈥檚 can be thought of as something that happens to everybody, but the brightest are better able to combat it. 鈥淚ntelligence doesn鈥檛 determine whether or not you develop dementia, it determines when,鈥� he told 麻豆传媒. He is now calling for urgent research into ways to boost intelligence.

But other Alzheimer鈥檚 experts reject his theory. 鈥淭his is a very radical and unorthodox interpretation of the data he鈥檚 got,鈥� says Richard Harvey of the Alzheimer鈥檚 Society in London.

Harvey says that people with more nerve cells in their brains are less affected by the cell loss associated with Alzheimer鈥檚. These people are also likely to be more intelligent. 鈥淚t鈥檚 also important to stress that Alzheimer鈥檚 is not something that happens to everybody. It is not a part of normal ageing,鈥� he says.

80-year experiment

Whalley and his colleagues identified 264 people living in Aberdeen, who had all taken an intelligence test at age 11 in 1932. Fifty of these people had developed late-onset dementia.

鈥淲e found that the contribution of lower mental ability to the risk of dementia is important after the age of 64, very important after the age of 72 and even more important after the age of 77,鈥� he says.

Late-onset dementia is defined as starting after age 64. 鈥淏ut clearly there is something from childhood that can stretch forward and affect how you鈥檙e going to be many years later,鈥� he says.

Whalley thinks 鈥榮ynaptic plasticity鈥� determines whether someone develops late-onset dementia. 鈥淎s you grow older, brain cells become less efficient at processing information. The better cells make more branches 鈥� and that compensatory response is key to the brain being able to maintain a reasonable performance in the face of dementia. I think this is more effective the brighter you are.鈥�

Brain plaques

To support his claim, Whalley points to a pathological study of the brains of people with and without symptoms of dementia.

鈥淭here were people with extensive pathological indications of Alzheimer鈥檚 at death but before death they had no symptoms of dementia. These people tended to be brighter,鈥� he says.

Harvey accepts the autopsy results. 鈥淵ou do see some features of Alzheimer鈥檚 鈥� such as amyloid plaques 鈥� in the brains of older healthy people. But this is not Alzheimer鈥檚,鈥� he insists. 鈥淎lzheimer鈥檚 is a combination of amyloid plaques, nerve cell death and cognitive impairment.鈥�

More at: Neurology (vol 55, p1456)