Increased risk of dementia for those who work more routine jobs

The brain is like a muscle; it needs to be worked out. The cognitive reserve hypothesis is a theory in neuroscience that seeks to explain why some people experience slower cognitive decline and a reduced risk of dementia despite underlying brain changes (like those associated with Alzheimer's disease). The explanation is that learning and using your brain throughout life might help you resist mental decline and dementia.

Two key ideas of the cognitive reserve hypothesis are:

• Brain as a Buffer. The hypothesis suggests that our brains have a built-in resilience or "reserve" that helps them cope with damage or age-related deterioration.
• "Use it or lose it" Mentality. It proposes that mentally stimulating activities throughout life build up this reserve. Think of it like exercising a muscle – the more you challenge your brain, the stronger it becomes.

Factors that contribute to cognitive reserve include education, mentally demanding jobs, intellectually stimulating hobbies and activities, and social engagement.

One expectation of this hypothesis is that mentally demanding jobs may be protective against mental decline and dementia. This prediction has been put to the test in various studies. Most recently, an article published in the journal Neurology provided evidence that routine jobs with low mental stimulation during middle age significantly increased the risk of cognitive decline and dementia later in life. 

The research, conducted by Dr. Trine Edwin and her team at Oslo University Hospital, analyzed the cognitive demands of 305 occupations using health and job data from 7,000 Norwegians tracked from their 30s into retirement (CNN). 

The study used a cohort design to track occupational cognitive demands from ages 30 to 65, assessing their impact on MCI and dementia in older adults, using data from the HUNT4 70+ Study conducted between 2017 and 2019 (which measured MCI and dementia after age 70). It employed group-based trajectory modeling and the routine task intensity (RTI) index to classify occupations by cognitive demand. Four groups were identified based on RTI scores: low, intermediate-low, intermediate-high, and high.

According to Edwin, examples of routine jobs include housekeepers, custodians, construction workers and mail carriers, whereas examples of mentally demanding jobs include lawyers, doctors, accountants, technical engineers, people in public service, and teachers (Figure 1). With respect to the last profession, Edwin explained that “Teachers have a lot of interaction with students and parents and have to explain and analyze information. It’s not so routine-oriented.” In general, "routine jobs" often involve repetitive tasks, while more "cognitively protective" careers demand greater adaptability and critical thinking.

The study found that participants in occupations with high routine task intensity (less cognitively demanding) faced a significantly higher risk of mild cognitive impairment (MCI) and dementia compared to those in more cognitively demanding jobs. Specifically, after adjusting for demographic and health factors, those with high RTI had a 74% higher risk of MCI and a 37% higher risk of dementia relative to those with low RTI. These results remained consistent even when additional adjustments for income and baseline health conditions were made. While college education reduces the negative impact of repetitive jobs, it doesn't eliminate the risk entirely.

These results are largely in line with research in the literature. One previous study found that work environments which stimulate the mind, as reported by individuals themselves, were linked to a reduced risk of dementia, even after accounting for educational backgrounds. Another study concluded that both educational attainment and the complexity of one's occupation independently contributed to protection against dementia.

A CNN piece describing the article interviewed the dementia expert Dr. Richard Isaacson who stressed the idea that just as we exercise our bodies, we need to exercise our brains with engaging work activities to fight dementia. He also highlighted the critical role of overall brain-healthy lifestyle choices.

Figure 1. Teaching is considered to be a mentally demanding job that can protect against dementia as you age.