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Is your job mentally stimulating? It could protect you against dementia

Is your job mentally stimulating? It could protect you against dementia
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How having a mentally stimulating job in midlife may protect against dementia later on

This is the 38th instalment in a series on dementia, including the research into its causes and treatment, advice for carers, and stories of hope.

A regular refrain from my mother was, “I wish I’d become a teacher”.

She would have made a very good teacher: she taught us at home when we were little. She taught a French-speaking friend’s daughter to speak English. She taught me how to teach my children to read and write.

She had exactly the right approach: she was patient, curious, made learning fun, and was a voracious reader.

I wonder now if having an occupation might have protected her from depression – she often articulated the loss she felt when her children went away to school as a key reason for her low moods.

I also wonder if having a job might have protected her from the dementia that took her life. The science says it might have done.

Dr Trine Holt Edwin, of Oslo University Hospital, in Norway. Photo: Anne Elisabeth Næss (Norwegian Health Association)

Dr Trine Holt Edwin, a geriatrician and postdoctoral fellow at the Oslo Clinical Dementia Research group at Oslo University Hospital, in Norway, recently authored a study that examined the connection between cognitive impairment and dementia in later life and occupation in midlife.

Holt Edwin’s findings – which examined people between the ages of 30 and 65 – found that the most cognitively challenging jobs help to build cognitive reserve.

A bigger or better cognitive reserve increases the brain’s resilience and flexibility, and allows for cognitive performance that is better than expected later in life, given the degree of life-course-related brain changes or disease.

The cognitive reserve hypothesis, she says, presupposes that “cognitive abilities acquired through education and other cognitively stimulating activities throughout the lifespan can delay the onset of mild cognitive impairment and dementia”.

Holt Edwin’s study, of more than 7,000 Norwegians across 305 different occupations, found that those who held the least mentally challenging – or menial – jobs had a 66 per cent greater risk of mild cognitive impairment, and a 31 per cent greater risk of dementia, after the age of 70 compared with those in more mentally demanding positions.

Yaakov Stern, an American cognitive neuroscientist and professor of neuropsychology at Columbia University in New York state, coined the term “cognitive reserve”. Photo: Columbia University

The phrase “cognitive reserve” was coined by Professor Yaakov Stern, a neuropsychologist and chief of the Cognitive Neuroscience Division in the Department of Neurology at Columbia University in the US state of New York.

Stern published a paper in the early 1990s that observed people with higher education were less likely to develop Alzheimer’s disease. When he presented it at the Academy of Neurology, friends and colleagues made fun of the idea.

He used “cognitive reserve” to differentiate it from the “brain reserve” described by Robert Katzman a few years previously.

New research suggests that it is never too late, or a waste of time, to start learning something new. Photo: Shutterstock

Katzman published research in the late 1980s based on the examination of the brains of elderly residents of a care home.

He found a number of their brains showed significant pathology of Alzheimer’s, yet their cognition ranked in the top 20 per cent of the nursing home residents – as good as, or better, than residents without any signs of Alzheimer’s in their brain.

Katzman concluded that this was because these people had bigger, heavier brains with more neurons and synapses, so they had more brain to lose in the face of dementia.

Katzman was a pioneer in the field of Alzheimer’s; his work demonstrated how widespread the illness actually was. When he published research on the prevalence of the illness in China, he concluded that people with higher levels of education appeared to have a lower incidence of dementia.

When he read this, Stern assumed the findings were flawed.

“They were using a mental status exam and I felt sure – of course – that people with higher education would do better on that test,” he said. “I felt it needed an incidence study – starting with people who were not demented and following them over time.”

Jobs ranked as most mentally stimulating – and therefore able to build up greater cognitive reserve – included teachers and university professors. Photo: Shutterstock

Stern and his team set out to do exactly that and found that people with fewer than eight years of education had twice the risk of developing dementia compared to those with more.

They also found that people with “low lifetime occupational attainment” bore a similar risk. The implication of these findings, Stern concluded, was that educational and occupational experiences imparted a reserve against the expression of Alzheimer’s pathology.

Holt Edwin’s results support this hypothesis “by showing that cognitive abilities acquired through both education and occupation during early [life] and midlife appear to offer resilience against cognitive decline”.

Categorising individuals according to the level of an occupation’s complexity versus how routine-oriented their work was, the scientists found the jobs with the “most mentally stimulating trajectory” were the ones that seemed to offer greatest protection.

More mundane work – that of cleaners, mail carriers and road workers – was among the least mentally challenging.

Pamela Almeida Meza, a researcher at University College London. Photo: www.researchgate.net/profile/Pamela-Almeida-Meza

Researcher Pamela Almeida-Meza, at University College London, found that even those who were not afforded the same educational or employment advantage can make up for the losses in learning, by reading for example.

She refers to the 1946 British National Birth Cohort study – a study arranged by social class and initially consisting of 5,362 people chosen at random from all births in England, Scotland, and Wales during a single week in March 1946 – as evidence of this.

At the time, she says, there were few women in higher education or senior positions at work, but many were self-educating, which had a positive impact ultimately on brain health.

If we were to extrapolate our results, Holt Edwin adds, “You could say that our study shows that it is never too late, or a waste of time, to start learning something new”.

All cognitively demanding activities later in life contribute to strengthening one’s cognitive reserve, she says, even if you are not working and did not work in an especially cerebral or taxing position.

Ironically, given my mother’s voiced wish that she had been a teacher, the jobs ranked as most stimulating were teachers and university lecturers.

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