Doctors and directors are better protected from dementia than drivers and fruit pickers, according to new research.
Experts with University College London discovered doing more mentally stimulating jobs may postpone the onset of dementia, by reducing the level of harmful proteins that prevent brain cells from forming new connections.
Researchers believe the risk of dementia is 50 per cent higher in people with unstimulating jobs, including lorry drivers, welders, and cashiers, rather than those employed as barristers, editors, or civil servants.
Cognitive stimulation at work takes place over decades, and adds up to tens of thousands of hours, lasting longer than specific mind-building techniques or hobbies.
"Our findings support the hypothesis that mental stimulation in adulthood may postpone the onset of dementia," said lead author Professor Mika Kivimaki of UCL. "We found the levels of dementia at age 80, seen in people who had experienced high levels of mental stimulation, was already observed at age 78.3 in those who had experienced low mental stimulation.
"This suggests the average delay in disease onset is about one and half years, but there is probably considerable variation in the effect between people."
Researchers say mental stimulation could make the difference by reducing processes called axonogenesis and synaptogenesis, which create harmful proteins which prevent brain cells from forming new connections.
The findings are based on studies from the U.K., U.S., and Europe, and looked at a number of factors in over 100,000 participants, including chronic disease, disability, and mortality.
UCL's results are published in The BMJ.