A busy brain at work has its cognitive merits later in life

Individuals who held cognitively demanding jobs between the ages of 30 and 60 had a lower risk of mild cognitive impairment (MCI) and dementia after 70 years, findings from the HUNT4 70+ study suggest.

“We examined the demands of various jobs and found that cognitive stimulation at work during different stages in life (30s, 40s, 50s, and 60s) was linked to a reduced risk of MCI after the age of 70,” noted study investigator Dr Trine Holt Edwin from the Oslo University Hospital, Oslo, Norway, in a press release. [https://www.aan.com/PressRoom/Home/PressRelease/5165, accessed May 16, 2024]

Using a cohort study design, the investigators evaluated the association between registry-based trajectories of occupational cognitive demands in over 7,000 individuals (49.8 percent women). Based on the longitudinal routine task intensity (RTI) index for 305 unique occupations in Norway, four RTI trajectory groups were identified: low RTI (n=1,431), intermediate-low RTI (n=1,578), intermediate-high RTI (n=2,601), and high RTI (n=1,393). Of note, lower RTI scores signify a more cognitively demanding job. [Neurology 2024;102:e209353]

After the age of 70, study participants completed memory and thinking assessments to determine whether they had MCI. Over 40 percent of individuals with the lowest cognitive demands were diagnosed with MCI. In the group of participants with the highest cognitive demands, the corresponding rate was 27 percent.

In the group of individuals with the lowest cognitive demands, the most common jobs were custodians and mail carriers. Among those with the highest cognitive demands, the most common job was teaching.

After adjusting for age, sex, and education, individuals in the high RTI group had a higher risk of MCI (relative risk ratio [RRR], 1.74, 95 percent confidence interval [CI], 1.41–2.14) and dementia (RRR, 1.37, 95 percent CI, 1.01–1.86) than those in the low RTI group.

Sensitivity analysis

A similar pattern was observed on sensitivity analysis after adjusting for age, sex, education, income, and baseline health-related factors, both for MCI (RRR, 1.66, 95 percent CI, 1.35–2.06) and dementia (RRR, 1.31, 95 percent CI, 0.96–1.78).

These findings imply that those with the lowest cognitive occupational demands had a 66-percent higher risk of MCI and 31-percent higher risk of dementia compared with the group of individuals who had the highest cognitive demands at work.

Cognitively challenging job crucial for brain health

The cognitive reserve hypothesis suggests that cognitively stimulating work delays the onset of MCI and dementia, the researchers noted. “However, the effect of occupational cognitive demands across midlife on the risk of these conditions is unclear.”

In the study, the investigators measured the degree of cognitive stimulation that the study participants experienced during the performance of their job. The tasks assessed – routine and nonroutine – were the skill sets required for different jobs.

Routine tasks were either manual (jobs that demanded speed, required control over equipment, involved repetitive motions) or cognitive (those that required precision and accuracy of repetitive tasks such as bookkeeping and filing).

Nonroutine tasks were either analytical (activities involving analysing information, engaging in creative thinking, interpreting information for others), interpersonal (refer to establishing and maintaining personal relationships, motivating others, coaching), or cognitive (include public relations, computer programming).

“Our findings highlight the value of having a job that requires more complex thinking as a way to possibly maintain memory and thinking in old age,” concluded Edwin and colleagues. “The results indicate that both education and doing work that challenges your brain during your career play a crucial role in lowering the risk of cognitive impairment later in life.”

“Further research is required to pinpoint the specific cognitively challenging occupational tasks that are most beneficial for maintaining thinking and memory skills,” the investigators added.