Alzheimer's linked to lowbrow jobs or Mentally stimulating careers may protect against dementia

A mentally stimulating career may help to reduce the risk of Alzheimer's disease, research suggests. According to a study carried out in the United States, those who develop the debilitating form of dementia are more likely to have had jobs that do not tax the brain.

The discovery lends weight to the 'use it or lose it' theory, says Kathleen Smyth of Case Western Reserve University in Cleveland, Ohio, who led the research. Experts have previously suggested that keeping the mind active, through reading or crossword puzzles, can help to stave off dementia in old age.

The latest work, however, shows that mental stimulation throughout life can influence the development of Alzheimer's. The researchers examined 122 people with Alzheimer's disease and 235 healthy subjects, and compared the mental demands they had faced throughout their careers, from their twenties right through to their fifties.

The average level of mental strain on the two groups was equal during their twenties. But those without Alzheimer's tended to have had jobs that were more mentally taxing from their thirties through to retirement, the researchers report in the journal Neurology. "In their thirties, forties and fifties there was a divergence that persisted," Smyth says.

High-powered jobs

The researchers are not sure exactly how the effect works. Perhaps Alzheimer's disease has an early impact that prevents sufferers from entering mentally demanding professions such as writing, accountancy or law, Smyth suggests.

But it may be more likely that the brain really does benefit from sustained activity, rather than a lifetime spent working in a factory. Smyth suggests that people who stimulate their minds might build up a reserve of nerve cells in the brain. This would allow them to remain clear-headed even as their brains became clogged with the clots of protein that characterize Alzheimer's.

Alternatively, those who exercise their grey matter might simply be better practised at thinking. This would make them more likely to perform well in the mental tests used to diagnose the disease, suggests Clive Ballard, director of research at the Alzheimer's Society, a British charity. "Are they really at lower risk of the disease or are they just better at doing tests?" he asks.

Ballard also suggests that, as people with intellectual careers tend to enjoy higher socioeconomic status, they may have better access to healthcare. He points to the recent suggestion that hormone-replacement therapy may protect against Alzheimer's. In actual fact, he stresses, the effect is probably due to the more privileged lifestyles of those who use the therapy.

Ballard does concede that the latest study is an improvement on previous efforts to compare Alzheimer's sufferers with healthy controls. "Case-control studies are always tricky," he says. "But what is different about this is that it is done decade by decade, so it is better informed."

Nature