A recent study published in the journal Neurology provides evidence that individuals engaged in cognitively stimulating occupations throughout their midlife — specifically their 30s through 60s — are less likely to develop mild cognitive impairment (MCI) and dementia after the age of 70. This research underscores the potential of mental engagement at work to bolster cognitive function well into old age, marking a significant advance by employing objective data to substantiate these findings.
Mild cognitive impairment (MCI) is a condition characterized by a noticeable decline in cognitive abilities, including memory and thinking skills, which is greater than what might be expected for a person’s age. However, this decline isn’t severe enough to interfere significantly with daily life or independent function, which distinguishes MCI from more severe forms of cognitive impairment like dementia.
People with MCI are at an increased risk of developing dementia, a broader term for conditions characterized by a decline in memory, language, problem-solving, and other thinking skills that affects a person’s ability to perform everyday activities. Alzheimer’s disease is the most common form of dementia, though there are several other types, each with its own underlying causes and symptoms. The progression from MCI to dementia can profoundly impact the quality of life, not only for those suffering from these conditions but also for their families and caregivers.
As populations continue to age, the incidence of these conditions is expected to rise, increasing the burden on healthcare systems and societies. Therefore, identifying factors that could potentially delay or prevent the onset of MCI and dementia is critical.
Previous research has supported the “cognitive reserve” hypothesis, which suggests that intellectual skills gained through education and challenging mental activities across one’s life can delay the onset of cognitive impairments. The workplace, with its array of intellectually engaging tasks, stands as a key area of interest. Although many studies have indicated that demanding jobs can mitigate the risk of cognitive decline, results have been inconsistent, often complicated by confounding factors like education and socioeconomic status.
To investigate the relationship between occupational cognitive demands during midlife and the risk of developing mild cognitive impairment (MCI) and dementia after the age of 70, a team of researchers from Columbia University Mailman School of Public Health, the Columbia Aging Center, and the Norwegian Institute of Public Health utilized data from the Trøndelag Health Study’s 70+ substudy (HUNT4 70+), which is part of a large, ongoing population-based health survey in Trøndelag County, Norway.
The study involved a total of 9,930 participants aged 70 to 105 years, who were residents of the northern part of the county and had participated in the fourth wave of the study between 2017 and 2019. The researchers utilized Norwegian administrative registry data to track the occupational history of each participant. They collected data on occupations held at various points throughout each participant’s life — specifically 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 metric called Routine Task Intensity (RTI). RTI quantifies the degree of routine versus non-routine cognitive tasks involved in a job, thus serving as an indicator of occupational cognitive demand.
The participants’ cognitive status was assessed through clinical evaluations 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). The evaluations included cognitive tests, interviews with participants and their next-of-kin, and reviews of medical records to determine whether participants had MCI, dementia, or no cognitive impairment.
The researchers identified four distinct trajectories of occupational cognitive demands from ages 30 to 65, categorized based on the level of RTI. 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 “primary education teaching associate professionals” and “secondary education teaching professionals.” In the intermediate-low RTI group, with moderately high cognitive demands, the most common jobs were “child care workers” and “nurses.”
The intermediate-high RTI group, which faced lower cognitive demands than the previous groups, mostly included “shop salespersons and other salespersons” and “nursing assistants, and care assistants.” Finally, the high RTI group was dominated by “helpers and cleaners in offices and other establishments” and “mail carriers and sorting clerks.”
The 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 the age of 70 compared to those in 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, those in the high RTI group were 37% more likely to develop dementia compared to 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 provide a protective effect against cognitive decline.
“Our study highlights the importance of mentally challenging job tasks to maintain cognitive functioning in later life,” said Vegard Skirbekk, a professor of Epidemiology at Columbia Mailman School of Public Health and Columbia Aging Center who initiated the project.
According to first author Trine Holt Edwin from Oslo University Hospital, “This study shows the importance of education and cognitively stimulating work life for cognitive health in older age.”
Further analysis adjusting for demographic and socioeconomic factors such as age, sex, and education level revealed that the protective effect of high cognitive demands was somewhat attenuated but still significant. This indicates that while factors like education also play a crucial role in cognitive health, the cognitive demands of one’s occupation independently contribute to reducing the risk of MCI and dementia.
“Education confounded most, but not all, of the association between occupational cognitive demands and MCI and dementia, suggesting that both education and occupational complexity matter for MCI and dementia risk,” Edwin explained..
Interestingly, when additional adjustments were made for health-related and lifestyle-related factors, the association between occupational cognitive demands and the risk of dementia weakened and was no longer statistically significant. However, the trend remained, suggesting that cognitive demands during working life are an important factor, though not the sole determinant, of cognitive health in later life.
The findings advance the field in several ways, according to the authors. “First, occupational cognitive demands have often been assessed via retrospective, subjective evaluations. Additionally, our utilization of registry data on occupational histories strengthens the existing evidence,” remarked Yaakov Stern, who is a principal investigator of the project at Columbia University.
While the study’s findings are valuable and suggest a protective effect of cognitive job demands, they do not prove that engaging in such work directly causes a reduction in dementia risk. There could be other factors at play that influence both a person’s occupational choices and their cognitive health. For example, individuals with higher inherent cognitive abilities might both seek out and perform better in complex jobs and be more resilient to cognitive decline due to these underlying abilities, rather than the job itself providing the protective effect.
In addition, the assessment of cognitive demands relied on historical job data, which may not fully capture the nature of past job requirements. The study focused on a Norwegian population, which might limit the generalizability of the findings to other cultural and economic contexts.
Looking ahead, the study’s authors advocate 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 in shaping long-term cognitive health.
“Overall, our study demonstrates that high occupational cognitive demands are related to lower risks of MCI and dementia in later life,” noted Skirbekk. “However, we recommend the commissioning of further research to validate these findings to pinpoint the specific occupational cognitive demands that are most advantageous for maintaining cognitive health in old age.”
The study, “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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