Routine occupations associated with 37% increase in dementia risk

A recent study published in the journal Neurology provides evidence that people engaged in cognitively stimulating occupations throughout their lives – particularly between the ages of 30 and 60 – are less likely to develop mild cognitive impairment (MCI) and dementia after age 70. This research highlights the potential of mental engagement at work to strengthen cognitive function into old age, marking a significant advance through the use of objective data to support these findings.

Mild cognitive impairment (MCI) is a condition characterized by a notable decline in cognitive abilities, including memory and thinking skills, that is greater than would be expected for a person’s age . However, this decline is not severe enough to significantly interfere with daily life or independent functioning, which distinguishes MCI from more severe forms of cognitive impairment like dementia.

People with MCI are at increased risk of developing dementia, a broader term for conditions characterized by a decline in memory, language, problem solving and other thinking skills that affect the ability to person to carry out daily activities. Alzheimer’s disease is the most common form of dementia, although there are several other types, each with their own causes and underlying symptoms. The progression from MCI to dementia can have a profound impact on quality of life, not only for people suffering from these conditions, but also for their families and caregivers.

As the population continues to age, the incidence of these conditions is expected to increase, increasing the burden on health systems and societies. Therefore, it is essential to identify factors that may delay or prevent the onset of MCI and dementia.

Previous research has supported the “cognitive reserve” hypothesis, which suggests that intellectual skills acquired through education and stimulating mental activities throughout life can delay the onset of cognitive impairments. The workplace, with its range of intellectually engaging tasks, is a key area of ​​focus. Although numerous studies have indicated that demanding jobs can mitigate the risk of cognitive decline, results have been inconsistent, often complicated by confounding factors such as education and socioeconomic status.

To study the relationship between cognitive job demands during midlife and the risk of developing mild cognitive impairment (MCI) and dementia after age 70, a team of researchers from the Mailman School of Public Health at Columbia University, the Columbia Aging Center and the Norwegian Institute of Public Health used data from the 70+ substudy of the Trøndelag Health Study (HUNT4 70+), which is part of a larger survey in population health course in Trøndelag County, Norway.

The study included a total of 9,930 participants aged 70 to 105, residing in the northern part of the county and who participated in the fourth wave of the study between 2017 and 2019. Researchers used data from the registry Norwegian administration to monitor the professional situation. history of each participant. They collected data on occupations held at different points in each participant’s life, particularly during their 30s, 40s, 50s, and 60s.

These occupational data were combined with information from the Occupational Information Network (O*NET) database, which provides detailed descriptions of the cognitive and physical demands of various occupations. This allowed the researchers to calculate the cognitive demands of each occupation using a measure called routine task intensity (RTI). RTI quantifies the degree of routine and non-routine cognitive tasks involved in a job, thereby serving as an indicator of occupational cognitive demand.

Participants’ cognitive status was assessed through clinical assessments conducted as part of the HUNT4 70+ study. These assessments were performed by healthcare professionals using standardized diagnostic tools and criteria, including the DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition). Assessments included cognitive testing, interviews with participants and their next of kin, and reviews of medical records to determine whether participants had MCI, dementia, or no cognitive impairment.

Researchers identified four distinct trajectories of occupational cognitive demands between ages 30 and 65, categorized by RTI level. These categories ranged from low RTI, indicating high cognitive demands, to high RTI, indicating low cognitive demands.

In the low RTI group, the predominant occupations were “associate primary education professionals” and “secondary education teaching professionals”. In the intermediate-low RTI group, with moderately high cognitive demands, the most common jobs were “educators” and “nurses.”

The intermediate-high RTI group, which faced lower cognitive demands than the previous groups, mainly included “store salespeople and other salespeople” and “caregivers and nursing assistants.” Finally, the high RTI group was dominated by “helpers and cleaners in offices and other establishments” and “postmen and sorting clerks”.

Results showed that individuals in the lowest RTI category, which corresponds to the most cognitively demanding occupations, had a significantly lower risk of developing MCI and dementia after age 70 compared to to those belonging to the higher RTI categories. Specifically, participants in the high RTI group were 74% more likely to develop MCI compared to those in the low RTI group. For dementia, people in the high RTI group were 37% more likely to develop dementia than their counterparts in the low RTI group.

This finding suggests that engaging in work that requires higher levels of cognitive processing and problem solving may have a protective effect against cognitive decline.

“Our study highlights the importance of mentally stimulating work tasks in maintaining cognitive functioning later in life,” said Vegard Skirbekk, a professor of epidemiology at the Columbia Mailman School of Public Health and the Columbia Aging Center who launched the project.

According to first author Trine Holt Edwin from Oslo University Hospital, “this study shows the importance of education and a cognitively stimulating working life for the cognitive health of older adults. »

Further analysis, controlling for demographic and socioeconomic factors such as age, gender, and education level, found that the protective effect of high cognitive demands was somewhat attenuated, but nonetheless significant. This indicates that although factors such as education also play a crucial role in cognitive health, the cognitive demands of the occupation independently contribute to reducing the risk of MCI and dementia.

“Education mediated most, but not all, of the association between cognitive job demands and MCI and dementia, suggesting that education and job complexity are both important for MCI risk and dementia,” Edwin explained.

Interestingly, when additional adjustments were made for health and lifestyle factors, the association between cognitive job demands and dementia risk weakened and was no longer statistically significant. However, the trend persists, suggesting that cognitive demands during working life are an important, although not unique, factor in cognitive health later in life.

The findings advance the field in several ways, according to the authors. “First, cognitive job demands have often been assessed through retrospective and subjective assessments. Additionally, our use of employment history registry data strengthens existing evidence,” noted Yaakov Stern, lead researcher on the project at Columbia University.

Although the study results are valuable and suggest a protective effect of the cognitive demands of work, they do not prove that engaging in such work directly leads to a reduction in dementia risk. There could be other factors at play that influence both a person’s career choices and their cognitive health. For example, individuals with higher inherent cognitive abilities might both seek and perform better in complex jobs and be more resilient to cognitive decline due to these underlying abilities, rather than the job itself providing a protective effect.

Additionally, the assessment of cognitive demands relied on historical job data, which may not fully reflect the nature of past job demands. The study focused on a Norwegian population, which might limit the generalizability of the results to other cultural and economic contexts.

Looking ahead, the study authors call for further research to explore the specific types of cognitive activities that are most beneficial and to extend these findings to more diverse populations. Additionally, there is a need to understand how cognitive and physical demands interact to shape long-term cognitive health.

“Overall, our study demonstrates that high job cognitive demands are linked to lower risks of MCI and dementia later in life,” Skirbekk noted. “However, we recommend commissioning further research to validate these findings to identify specific occupational cognitive demands that are most beneficial for maintaining cognitive health in old age.”

The study titled “Trajectories of occupational cognitive demands and risk of mild cognitive impairment and dementia in later life” was authored by Trine H. Edwin, Asta K. Håberg, Ekaterina Zotcheva, Bernt Bratsberg, Astanand Jugessur, Bo Engdahl, Catherine Bowen, Geir Selbæk, Hans-Peter Kohler, Jennifer R. Harris, Sarah E. Tom, Steinar Krokstad, Teferi Mekonnen, Yaakov Stern, Vegard F. Skirbekk, and Bjørn H. Strand.

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