Mental function starts to decline in your 40s

The brain’s capacity for memory, reasoning and comprehension begins to wane much earlier than previously thought, it suggests.

While 60 has been cited as the age people experience a difference in their thinking abilities, the new study found decline could actually hit the middle-aged.

Researchers from the Centre for Research in Epidemiology and Population Health in France and University College London in the UK studied more than 7,000 people over a 10-year period.

Published online in the British Medical Journal (BMJ), their research focused on civil servants aged between 45 and 70 at the start of cognitive testing in 1997 to 1999.

Cognitive function was measured three times over a 10 year period to assess memory, vocabulary, hearing and visual comprehension skills.

Tasks included recalling in writing as many words beginning with the letter S as possible and as many animal names as could be thought of.

All cognitive scores, except vocabulary, declined among all age groups during the study, and there was evidence of faster decline among older people.

In men, there was a 3.6 per cent drop in reasoning after 10 years among those who were aged 45 to 49 at the start of the study, and 9.6 per cent among those aged 65 to 70. In women, the decline was 3.6 per cent and 7.4 per cent in the same age groups respectively.

The authors concluded: “Cognitive decline is already evident in middle age (45-49).”

They added: “Life expectancy continues to increase, and understanding cognitive ageing will be one of the challenges of this century. Poor cognitive status is perhaps the single most disabling condition in old age.”

The researchers said diseases such as dementia were now thought to be the result of long-term changes over at least 20 to 30 years.

There is enough evidence already to show the importance of healthy lifestyles and good heart health in impacting on the later risk of dementia.

For some risk factors, such as obesity, high blood pressure and high cholesterol, it is mid-life levels that seem to be more important than those measured at older ages, they said.

Dr Simon Ridley, head of research at Alzheimer’s Research UK, said: “Experts believe that Alzheimer’s disease, the most common cause of dementia, begins to develop in mid-life.

“Although this study didn’t look at dementia, it would be important to follow up these participants to see which people go on to develop the condition.

“It’s important to note that the group studied here was not representative of the population as a whole, and it would be helpful to see similar studies carried out in a wider sample.”