Research carried out in the United States has found that people diagnosed with Alzheimer's disease are more likely to have had less mentally demanding careers than those who do not get the disease.
Researchers from the Case Western Reserve University in Ohio examined the employment histories of 357 people aged over 60, 122 of whom suffered from Alzheimer's.
The team looked at the type of job and industry they had worked in, the number of years they spent in their job, and their most important job activities.
And according to a report published in Neurology, the scientific journal of the American Academy of Neurology, those with Alzheimer's tended to have less mentally demanding careers.
In particular, the researchers discovered that while most of the group studied had jobs with about the same level of mental demands when they were in their 20s, those who did not have Alzheimer's went on to do more mentally demanding jobs in their 30s, 40s and 50s.
In contrast, the Alzheimer's patients continued to work in jobs that required the same mental demands as they moved from their 20s to their 50s.
Those who went on to be diagnosed with the disease did not. They were more likely to spend their working lives in physical jobs and the mental demands of their jobs did not change significantly over the decades.
Dr Kathleen Smyth, one of the Case researchers, said that it was unclear what the link is other studies have also suggested that keeping the brain active can protect against Alzheimer's.
“It could be that the disease has a very early effect on the individual's capacity to pursue a mentally challenging occupation,” she said “or, it could be that higher levels of mental demands result in increased brain cell activity, which may help maintain a ‘reserve’ of brain cells that resists the effects of Alzheimer's disease.”
However, the researchers said other factors may also be involved. In particular, the study did not look at the socio-economic background of the participants.
"Variations in income, access to healthcare, better nutrition and other factors related to socio-economic status could be responsible in part for our findings," Dr Smyth added.