Dementia: Repetitive, routine jobs may raise cognitive decline risk

For the study, researchers investigated the work and later-life cognitive health of 7,003 people in Norway, representing 305 unique types of jobs.

The research is part of a larger project called “Changing lives, changing brains,” led by the Norwegian Institute of Public Health, Columbia University New York, and the University of Pennsylvania.

The researchers scored jobs using a Routine Task Intensity (RTI) scale. Routine tasks are those that are the least cognitively challenging. Such occupations often require speed and precision. However, since these are repetitive tasks, they may require less mental involvement. Examples are factory work, filing, and bookkeeping.

Non-routine tasks — which were assigned lower RTI grades — require more cognitive involvement. They involve regular novel challenges that may require analysis, creativity, or the strategic interpretation of raw information.

Some of these jobs may be interpersonal, where the worker must continually engage, coach, and coax others. Examples of non-routine tasks include computer programming and public relations.

The researchers divided the jobs into four groups:

• The most frequent occupations in the high RTI group were helpers and cleaners in offices and other establishments.
• In the intermediate high RTI group were a preponderance of store salespersons and other retail sales personnel.
• Child-care workers and nurses were most commonly assigned to the medium-low RTI group.
• The lowest RTI group was most often represented by primary and secondary education teaching professionals.

Of people in the high RTI group, 42% were diagnosed with cognitive impairment at ages 70 compared to the 27% in the low RTI group.

While people of differing ages and backgrounds tend to find themselves in certain occupations, the researchers factored in income and baseline health-related factors and found that their findings remained essentially unchanged.

Edwin explained the results of the new study build on the “cognitive reserve hypothesis.”

The study’s findings “support this hypothesis by showing that cognitive abilities acquired through both education and occupation during early and midlife appear to offer resilience against the brain change associated with age-related cognitive decline,” Edwin added.

For some people, maintaining cognitive reserve may be a matter of “use it or lose it” to some extent. However, our knowledge of how dementia develops allows for other possible causative factors, such as genetics and environment.

Snorri Bjorn Rafnsson, PhD, associate professor of Ageing and Dementia at the University of West London, noted that although the phrase is most often applied to exercising, it can still serve as a useful motto in a neurological context. Rafnsson was not involved in the study.

“New neurons are stimulated to survive by engaging in neurophysiological activity related to new and challenging learning experiences. Cognitively stimulating work could thus boost neuronal activity and help maintain a fit brain,” Rafnsson told MNT.

Skirbekk noted that not “using it” can result in other influences tied to cognitive health.

“Sedentary lifestyles, social isolation, and limited social interaction can adversely affect cognitive development throughout adulthood and lead to poor cognitive outcomes,” Skirbekk said.

An observational study such as this cannot establish a person’s job is a direct cause of cognitive issues later in life.

It can only be established that by observing job types and cognitive impairment in individuals at age 70, certain routine task intensity groups align with certain outcomes.

Vegard Skirbekk, PhD, professor at Columbia Aging Center, Columbia University and a senior researcher at the Norwegian Institute of Public Health, pointed to the difficulty in confirming a causal connection in this area.

“Numerous studies delve into this topic, but pinpointing causality proves challenging due to the self-selection of individuals into specific occupations,” Skirbekk told MNT.

“Thus, unraveling any relationship between work demands and cognition becomes complex,” he added.

People with jobs that are not mentally stimulating may be troubled by the findings of this study, but Rafnsson said there are other ways to preserve brain health and prevent cognitive decline.

“Our knowledge about how lifestyle factors, cognitively stimulating activities, social connections, etc., influence brain health has increased greatly over the past years and decades,” Rafnsson noted.

“People whose jobs are not mentally stimulating can still engage in a range of other useful activities — e.g., hobbies that are stimulating and fun; maintaining social relationships with friends and family — that can benefit their brains as well their overall health and well-being.”

— Snorri Bjorn Rafnsson, PhD, associate professor of aging and dementia

Of course, as Skirbekk pointed out, some people might “consider finding work that is cognitively challenging if that is an opportunity.”