Published on: April 16, 2017
by Mark Macaskill for The Sunday Times:
A pioneering study of 35,000 Scots has found that pre-adolescent girls with low IQs are more likely to develop dementia than girls of higher intelligence.
Scientists behind the research — the first to examine the incidence of dementia between the sexes — were surprised, however, not to observe a similar relationship for boys.
The link between lower childhood IQ and risk of dementia was “clearly evident” in women “but less so” in men, according to new research by the University of Edinburgh and University College London.
Previous studies have linked childhood intelligence and dementia, but the latest is the first to conclude that the risk is not the same in men and women.
Scientists cannot explain the finding but factors such as social class or quality of pre-school education could play a role.
“Early life cognitive ability has been linked to subsequent dementia risk but studies to date have been small and none has examined sex differences,” said Dr Tom Russ of the Alzheimer Scotland Dementia Research Centre and the Centre for Dementia Prevention, both at Edinburgh University.
“Our main findings are that an association between lower childhood IQ and increased dementia risk was clearly evident in women, but less so in men. This research helps us move towards an understanding of dementia as not being a disease of old age — it is a disease of the whole life span.”
Russ’s work, funded by Alzheimer Scotland and to be published in the scientific journal Epidemiology, could help shed new light on the potential triggers for dementia, an illness that affects about 850,000 people in the UK.
For the study, data that was gathered from more than 35,000 men and women who were born in Scotland in 1921 and took an IQ test at 11 years of age was analysed. By the time they reached between 65 and 91 years of age, 1,231 men and 2,163 women had developed dementia.
Alzheimer’s dementia — the most common type of dementia — is known to be more common in women, prompting speculation that it is because women tend to live longer than men.
However, Russ and colleagues were surprised to find that early cognitive ability was a strong predictor of the condition. Among men, this was true only among those with the very lowest IQs. In women, the link was evident across all levels of intelligence. It suggests that greater efforts to improve cognitive ability, particularly among young girls, could reduce overall dementia rates in decades to come.
Jim Pearson, director of policy and research at Alzheimer Scotland, said: “This new study adds to our understanding of the potential life-long factors that may increase the risk of developing dementia.
“It also highlights the importance in recognising the role of early years’ development in supporting better life chances and health outcomes in later life.”
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