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The BBC's Richard Bilton
"There comes a point when a brain starts to feel its age"
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Wednesday, 20 December, 2000, 12:22 GMT
Mental decline 'starts in forties'
Mental decline starts 'after 40'
Mental decline starts 'after 40'
Some say that life begins at 40, but scientists have discovered that so does the process of mental decline.

Research by psychologists suggests that even the most quick witted people start to slow down mentally past the age of 45.

From then on further decline is inevitable with each passing year.

By middle-age you can be 10% to 15% slower

Professor Keith Wesnes, Cognitive Drug Research Ltd
A team of psychologists from Cognitive Drug Research Ltd in Reading carried out tests on 2,282 healthy volunteers aged between 18 and 87.

They tested routine abilities such as time taken to remember names and faces, speed of reaction to situations, concentration on tasks and decision making.

Lead researcher Professor Keith Wesnes said: "By middle-age you can be 10% to 15% slower in a number of functions than your were in your 20s.

"You're not concentrating as well and you can't focus and ignore distraction to the same extent as you used to.

"You become slightly forgetful, and might not remember what you walked into a room for, or take a long time to recall someone's name.

"You're less able to bring things to the front of your mind quickly."

The results of the study clearly showed that until the mid-40s people's mental faculties remained unchanged.

But after this time thinking-speed showed a marked decline which continued at a constant rate into old age.

The ability to remember words after a delay was especially affected.

Slow down theory

Scientists do not know why the brain starts to slow down past a certain age.

Maybe they can't process the information as quickly, but they know the short cuts

Dr James Semple, Addenbrooke's Hospital
One theory is that cells in the brain gradually lose the ability to communicate with each other via chemicals called neurotransmitters.

This in turn may cause brain cells to wither due to lack of stimulation.

An expert in brain chemistry, Dr James Semple, from Addenbrooke's Hospital, Cambridge, said: "It's probable that for some reason the efficiency of the transmitter system decreases in your 40s and 50s".

Dr Semple presented findings at the conference which showed that patients with Alzheimer's disease lose about 3% of their total brain volume each year.

People experiencing normal ageing lost less than 0.5%.

Dr Semple said middle aged people could rely on their greater experience to compensate for a slow down in their mental functioning.

Dr Semple said: "Old dogs have strategies and tricks they can use because they have experience working in the system.

"Maybe they can't process the information as quickly, but they know the short cuts."

Professor Wesnes said there was evidence that herbal supplements such as ginkgo could help speed up the over-forties.

In one recent trial, a group of middle-aged people showed a 7% mental improvement after taking a combination of ginkgo and ginseng.

The research findings were presented at the British Psychological Society's London conference on Tuesday.

Cognitive Drug Research Ltd specialises in studying the mental function of people taking part in pharmaceutical trials.

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