London: Memory and other brain functions begin to decline after the age of 45, say researchers.

The brain's capacity for memory, reasoning and comprehension starts waning in middle age rather than in the 60s, a study shows.

Experts say the finding is important because younger people should be encouraged to boost their brain power with healthier living.

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

The study looked at civil servants aged between 45 and 70 working in London, a daily reported on Friday.

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

In men, there was a 3.6 percent drop in reasoning after 10 years among those who were aged 45 to 49 at the start of the study and 9.6 percent among those aged 65 to 70.

In women, the decline was 3.6 percent and 7.4 percent in the same age groups, the Mail said quoting an online report published by the British Medical Journal.

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.

She said "Cognitive decline is already evident in middle age, between 45-49 years."

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.

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.

(Agencies)