Cognitively stimulating jobs tied to lower dementia risk
14/09- Individuals who get higher levels of cognitive stimulation at work may have a lower risk of dementia as they age than peers with less stimulating jobs, a new study suggests.
Researchers examined data on 107,896 participants in seven studies conducted by the IPD-Work consortium, including baseline measurements of cognitive stimulation at work via questionnaire and electronic health records on incident dementia.
Over 1.8 million person-years at risk, researchers identified 1,143 individuals with incident dementia.
Compared to people with low levels of cognitive stimulation at work, those with highly cognitively stimulating jobs were significantly less likely to develop dementia (hazard ratio 0.77), the authors report in The BMJ.
Crude incident dementia per 10,000 person-years was 4.8 cases among people with high levels of cognitive stimulation at work and 7.3 cases among workers with low levels of cognitive stimulation.
"Our data suggest that cognitive stimulation in adulthood may postpone the onset of dementia," said lead study author Mika Kivimaki of University College London in the UK.
The current analysis also examined data on cognitive stimulation and plasma proteins in a random sample of 2,261 participants from one study as well as proteins and dementia risk among 13,656 participants from two studies.
Cognitive stimulation was associated with lower levels of three plasma proteins that might inhibit axonogenesis and synaptogenesis and increase dementia risk, the study found.
"These three proteins adversely affect the way the brain cells form new connections, i.e. axonogenesis and synaptogenesis," Kivimaki said by email.
"Due to lower protein levels among individuals with cognitive stimulation in the workplace, the structural characteristics of the brain probably allow these people to better cope with brain pathology before clinical or cognitive changes emerge," Kivimaki said.
One limitation of the study, the authors note, is that they were unable to exclude residual confounding, particularly by childhood IQ. The researchers were also unable to account for the lifelong effects of different levels of cognitive stimulation due to the focus on working-age adults and the relatively low mean age at dementia diagnosis, the study team pointed out.
"The effect seen here could be due to the fact that initially more able select into mentally demanding occupations," said Serhiy Dekhtyar, an associate professor at the Aging Research Center at the Karolinska Institute in Stockholm, Sweden, who wrote an editorial accompanying the study.
It might not be that mental stimulation lowers dementia risk for these individuals, Dekhtyar said by email.
"Instead, it's but initial differences between people (either due to genes or early environments) that determine both their occupational environments and dementia," Dekhtyar said. "Without taking childhood cognition into account, it is difficult to say whether it is truly mental stimulation that matters."
However, decades of exposure to occupational environments may still play a role in dementia risk as people age, Dekhtyar said.
"Continued mental engagement at work can help promote cortical plasticity or help reduce the atrophy of cortical areas which would be deactivated in the face of low demands," Dekhtyar said. "It can also help further build up resilience against the progressively accumulating brain pathology, thus allowing to preserve cognitive function longer."
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