Having an interesting job in your forties may slash your risk of getting dementia in old age, a study has suggested.
Researchers claim mental stimulation may stave off the onslaught of the memory-robbing condition by around 18 months.
Academics examined more than 100,000 participants and tracked them for nearly two decades.
They spotted a third fewer cases of dementia among people who had engaging jobs which involved demanding tasks and more control — such as solicitors and doctors, compared to adults in 'passive' roles — such as cashiers.
And those who found their own work interesting also had lower levels of proteins in their blood that have been linked with dementia.
Keeping the brain active by challenging yourself regularly likely reduces the risk of dementia by building up its ability to cope with disease, experts say.
Dementia is the second biggest killer in the UK behind heart disease, according to the UK Government agency, the Office for National Statistics.
In the US, around 5 million people have the condition. Alzheimer's disease is the most common type of dementia, causing up to 70 percent of cases.
A plethora of studies have already suggested mental stimulation could prevent or postpone the onset of dementia.
But none found that mentally demanding hobbies, which may include reading, doing puzzles or going to museums, cut the risk.
The new study looked at jobs, which the academic said involved more engagement than hobbies, which often last less than an hour.
It was carried out by researchers from University College London, the University of Helsinki and Johns Hopkins University.
They looked into the cognitive stimulation and dementia risk in 107,896 volunteers, who were regularly quizzed about their job.
Volunteers jobs included interesting roles such as government officers, directors, physicians, dentists and solicitors.
Jobs with low brain stimulation included supermarket cashiers, vehicle drivers and machine operators.
The volunteers — who had an average age of around 45 — were tracked for between 14 and 40 years.
Jobs were classed as cognitively stimulating if they included demanding tasks and came with high job control.
Non-stimulating 'passive' occupations included those with low demands and little decision-making power.
Experts spotted 4.8 cases of dementia per 10,000 person years among those with interesting jobs, equating to 0.8 percent of the group.
Meanwhile, there were 7.3 cases per 10,000 person years among those with boring careers (1.2 percent).
Among people with jobs that were in the middle of these two categories, there were 6.8 cases per 10,000 person years (1.12 percent).
The study, published in the British Medical Journal, also looked at three protein levels in the blood among another group of volunteers.
These proteins are thought to stop the brain forming new connections, increasing the risk of dementia.
People with interesting jobs had lower levels of three proteins considered to be tell-tale signs of the condition.
The researchers noted the study was only observational, meaning it cannot establish cause and that other factors could be at play.