Keeping mentally active is key
Keeping the brain active by working later in life may be an effective way to ward off Alzheimer's disease, research suggests.
Researchers analysed data from 1,320 dementia patients, including 382 men.
They found that for the men, continuing to work late in life helped keep the brain sharp enough to delay dementia taking hold.
The study was carried out by the Institute of Psychiatry at King's College London.
It features in the International Journal of Geriatric Psychiatry.
Around 700,000 people in the UK currently have dementia and experts have estimated that by 2051, the number could stand at 1.7m.
It is estimated that the condition already costs the UK economy £17bn a year.
Dementia is caused by the mass loss of cells in the brain, and experts believe one way to guard against it is to build up as many connections between cells as possible by being mentally active throughout life. This is known as a "cognitive reserve".
There is evidence to suggest a good education is associated with a reduced dementia risk.
And the latest study suggests there can also be a positive effect of mental stimulation continued into our later years.
Those people who retired late developed Alzheimer's at a later stage than those who opted not to work on.
Each additional year of employment was associated with around a six week later age of onset.
Researcher Dr John Powell said: "The possibility that a person's cognitive reserve could still be modified later in life adds weight to the "use it or lose it" concept where keeping active later in life has important health benefits, including reducing dementia risk."
The researchers also admit that the nature of retirement is changing, and that for some people it may now be as intellectually stimulating as work.
Researcher Professor Simon Lovestone said: "The intellectual stimulation that older people gain from the workplace may prevent a decline in mental abilities, thus keeping people above the threshold for dementia for longer."
However, he added: "Much more research is needed if we are to understand how to effectively delay, or even prevent, dementia."
Rebecca Wood, chief executive of the Alzheimer's Research Trust, which funded the study, said: "More people than ever retire later in life to avert financial hardship, but there may be a silver lining - lower dementia risk."
However, Dr Susanne Sorensen, head of research at the Alzheimer's Society, said the small sample size of the study made it difficult to draw firm conclusions.
She said: "There could be a number of reasons why later retirement in men is linked with later onset of dementia.
"Men who retire early often do so because of health conditions, such as hypertension or diabetes, which increase your risk of dementia.
"It could also be that working helps keep your mind and body active, which we know reduces risk of dementia."
A spokesperson for the Department for Work and Pensions said it had carried out work showing that working beyond pension age had many positive effects.
"Not only can it mean more income, but also social networking and increased activity.
"We also find that many of today's older workers are choosing rejecting the cliff edge between work and retirement in favour of a gradual step down. And employers should help them to do this."