Memory and mental function may begin slipping at 45.

Memory and mental function may begin slipping at 45. (KTLA-TV)

A new study out of Europe suggests that the human brain starts going downhill much sooner than first thought.

The study, published Thursday in the British Medical Journal, suggests that age-related cognitive changes, which can be a sign of Alzheimer's disease and other types of dementia, begin as early as our mid-to-late 40s.

Previous studies suggested mental decline started in the 60s.

The researchers tracked the mental function of more than 7,000 British civil servants for a decade.

They studied several age groups, from 45 to 70.

Tests showed that men and women exhibited slight, yet measurable, signs of cognitive decline between the ages of 45 and 49.

They included declines in short-term memory, mental reasoning and verbal facility.

The changes were too small to be noticeable in everyday life, but the researchers say the findings have important implications for preventing dementia.

Experts say young people should boost their brain power through healthier living.

Heart-healthy habits, in particular, have been shown to be good for the brain.

In contrast, obesity, high cholesterol and a lack of exercise in midlife are all linked with an increased risk of dementia later on.