The brain’ skills can start to decline as early as 45, much earlier than previously thought, suggests a study published in the British Medical Journal.

A major study shows the brain’s capacity for memory, reasoning and comprehension starts waning in middle age rather than in the 60s.

Researchers say the finding is important because younger people should be encouraged to boost their brain power with healthier living, while some may benefit from medicines to stave off further decline.

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.

The study participants were civil servants aged between 45 and 70 working in London when cognitive testing began in 1997 to 1999.

Cognitive function was measured three times over 10 years 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.

The brain' skills can start to decline as early as 45, much earlier than previously thought, suggests a study published in the British Medical Journal

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

Dr. Archana Singh-Manoux, who led the study, said there had been debate over when mental skills started failing, with some researchers concluding there was little evidence of problems before 60.

But this was disproved by the study findings, she added.

Dr. Archana Singh-Manoux said: “Cognitive decline is already evident in middle age, between 45-49 years.

“The results for all tests, except vocabulary, showed significant declines in all age categories in both men and women.”

The study says diseases such as dementia are believed to take at least 20 to 30 years to develop but promoting healthy lifestyles and good heart health could help.

“There is emerging consensus that ‘what is good for our hearts is also good for our heads, making aggressive control of behavioural and cardiovascular risk factors as early as possible key targets for clinical practice and public health” it said.

Medicines and other medical interventions are more likely to work at an earlier age, so could be used in people whose cognitive decline is faster than the average, it said.

Previous research suggests around half of people with diagnosed mild cognitive impairment (MCI) develop Alzheimer’s.

In cases of MCI, a person has cognitive or memory problems which are more marked than typical age-related memory loss, but not yet as severe as those found in Alzheimer’s disease.

Dr. Anne Corbett, research manager of the Alzheimer’s Society in UK, said: “This large, important study adds vital information to the debate over when cognitive decline begins.

“However, the study does not tell us whether any of these people went on to develop dementia, nor how feasible it would be for GPs to detect these early changes.

“More research is now needed to help us fully understand how measurable changes in the brain can help us improve diagnosis of dementia.

“An early diagnosis is essential as it can provide access to support and potential treatments which can vastly improve people’s quality of life.”