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Mental performance improving in the over-90s

Educational differences don’t explain improvement in mental test scores

Louise Prime

Thursday, 11 July 2013

People who are in their nineties have better mental performance than those of a similar age a decade ago, research has shown. Authors of the study, published online today in The Lancet, say that slight improvements in educational attainment don’t account for the improvement in test scores. They add that their findings also challenge the idea that an ageing population necessarily results from frail and disabled elderly people living longer.

The researchers compared the mental performance of two cohorts of elderly people living in Denmark – all those born in 1905 still alive in 1998, aged 92-93 years (2262 people), and all those born in 1915 still alive in 2010, aged 94-95 years (1584 people). The participants took physical and cognitive tests, and gave interviews, designed to assess their mental impairment (mini mental state examination); fluency and recall abilities (cognitive composite score), depression symptoms, and ability to carry out activities of daily living. For the roughly 20% whose physical or mental handicap meant they could not respond personally, a proxy responder helped.

There was no significant difference between the groups’ physical performance test scores. But the 1915 cohort were almost a third (32%) more likely than the 1905 cohort to have reached the age of 93, and they also performed better in terms of both cognitive ability and activities of daily living. They had better mean test scores than the 1905 cohort – and even though they were on average two years older at the time of testing than the 1905 cohort had been, a much higher proportion gained maximum scores in the cognition tests.

The study’s authors looked at whether the improvements could have been the result of differences in educational attainment between the cohorts. But this reached statistical significance only for women, whose overall educational attainment was very low in both groups anyway, so the authors say this was unlikely to have accounted for the difference in mental performance.

They said: “Even after adjusting for the increase in education between the 1905 and 1915 cohorts, the 1915 cohort still performed better in the cognitive measures, which suggests that changes in other factors such as nutrition, burden of infectious disease, work environment, intellectual stimulation, and general living conditions also play an important part in the improvement of cognitive functioning.

“The study challenges speculations that the improving longevity is the result of the survival of very frail and disabled elderly people.”

The authors of a commentary on the study said: “The expectation of a continuing sharp rise in dementia prevalence in populations older than 80 or 90 years plays an important part in the alarming predictions about the future global burden of dementia, [but] the evidence for improved cognition at very old age provided by Christensen and colleagues challenges these extrapolations.”

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