Individuals with mentally stimulating jobs have less risk of dementia in later life than those who have non-stimulating employment, research suggests.
Scientists looked at over 100,000 participants across studies which were focused on connections between work-related factors and chronic disease, disability and mortality, from the US, Europe and the UK.
The study examined those in a range of different occupations, from forestry workers to civil servants and public sector employees, while the lead author suggested that findings support the idea that being mentally stimulated in adulthood may delay the onset of dementia.
It is already thought that cognitive stimulation can postpone or prevent the onset of dementia. However, these assumptions have been based on small sample sizes and short term-interventions, with inconsistent results produced, said researchers.
A possible explanation for the results of the large study is that cognitive stimulation is associated with lower levels of certain proteins which may inhibit some processes in the brain.
Those involved were tracked for an average of 17 years to see whether or not they developed dementia. Their cognitive stimulation at work was previously measured at the beginning of the study.
Lead author Professor Mika Kivimaki, from University College London’s Institute of Epidemiology and Healthcare, said: “Our findings support the hypothesis that mental stimulation in adulthood may postpone the onset of dementia.
“The levels of dementia at age 80 seen in people who experienced high levels of mental stimulation was 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.”
Cognitively stimulating jobs were defined by researchers as including demanding tasks and having a high job decision latitude or job control, for example senior government officers, production and operations managers, directors and chief executives.
Non-stimulating occupations were considered to be those with a lack of job control and with low demands such as cashiers, agricultural, fishery and related labourers, transport labourers and mobile-plant operators.
Due to longer hours spent at work, it is thought that exposure to cognitive stimulation lasts “considerably longer” than cognitive interventions or cognitively stimulating hobbies, said scientists.
The study found that, having taken influential factors into account, the incidence of dementia was 4.8 per 10,000 people in the high stimulation group, while it was 7.3 in the low stimulation group.
Potentially influential factors included age, sex, educational attainment and lifestyle.
It appeared that there was no difference between genders or those younger or older than 60. However, there was an indication that the association was stronger for Alzheimer’s disease compared to other types of dementia.
Dr Sara Imarisio, head of research at Alzheimer’s Research UK, said: “This large, robust study adds to a body of evidence suggesting that staying mentally active is important for helping reduce the risk of dementia.
“Previous research has suggested that keeping the brain active can help build cognitive reserve, a type of resilience that helps the brain ‘rewire’ its connections more easily and keep working for longer when diseases like Alzheimer’s take hold.
“This new research also identified proteins in people’s blood plasma that may be connected to this process, and further research should investigate this finding in more detail.”
She added: “Not everyone is able to choose the type of work they do, but studies like this highlight the importance of finding activities that help keep the brain active, whether it’s through work or hobbies.
“It’s not currently clear which activities are most helpful for building cognitive reserve, so whether it’s a stimulating job, reading or learning a language, finding something you enjoy is key.”
Additional reporting by PA