Cognitive stimulation reduces your dementia risk
This large study shows it is not only education, but cognitive stimulation that reduces your risk of dementia in old-age. This was associated with peripheral biomarkers. Very interesting and important
I am not surprised that the risk of dementia in old age is lower in people with cognitively stimulating jobs compared to those with non-stimulating jobs. The obvious confounder here is the level of education.
The overall effect, however, is small; i.e. a difference of ~2.5 incident cases of dementia per 10,000 person-years of follow-up between the low and the high stimulation groups.
The reduction in dementia risk with higher education is greater (34%) than the risk reduction associated with higher mental stimulation at work (23%). Accounting for education attenuates the point estimate for occupation by around a quarter. The latter is expected given that education is a strong determinant of occupational attainment and reduces your chances of dementia. The latter effect of education involves wider social determinants such as health behaviours, health literacy, cognitive enrichment, etc.
It seems that education trumps work simulation with greater risk reduction in those with high education and low work stimulation (27%) than in those with low education and high work stimulation (20%). Does this not indicate that education and not occupation should be where we focus our preventive strategies? Saying this cumulative exposure to both high education and high cognitive stimulation at work is associated with the greatest risk reduction of all, i.e. 37%. Will getting rid of all the ‘bullshit jobs’* that are not cognitively stimulating be feasible in the future?
What makes these findings really interesting is that cognitive stimulation is associated with lower levels of plasma proteins that potentially inhibit axonogenesis and synaptogenesis. This hints that the increased risk of dementia is linked to potential biological mechanisms. The importance of the latter can’t be underestimated as these potential biomarkers, if they prove to be surrogate markers of future dementia risk, could be used as a part of an intermediated endophenotype for small scale intervention studies; potentially as part of a multi-arm adaptive study.
In conclusion, a great study with lots to think about and discuss with my colleagues.
* Bullshit Jobs: A Theory is a 2018 book by anthropologist David Graeber that postulates the existence of meaningless jobs and analyzes their societal harm. He contends that over half of societal work is pointless, and becomes psychologically destructive when paired with a work ethic that associates work with self-worth. Graeber describes five types of meaningless jobs, in which workers pretend their role is not as pointless or harmful as they know it to be: flunkies, goons, duct tapers, box tickers, and taskmasters. He argues that the association of labour with virtuous suffering is recent in human history, and proposes universal basic income as a potential solution (Source Wikipedia).
Kivimäki et al. Cognitive stimulation in the workplace, plasma proteins, and risk of dementia: three analyses of population cohort studies. BMJ. 2021 Aug 18;374:n1804. doi: 10.1136/bmj.n1804.
Objectives: To examine the association between cognitively stimulating work and subsequent risk of dementia and to identify protein pathways for this association.
Design: Multicohort study with three sets of analyses.
Setting: United Kingdom, Europe, and the United States.
Participants: Three associations were examined: cognitive stimulation and dementia risk in 107 896 participants from seven population based prospective cohort studies from the IPD-Work consortium (individual participant data meta-analysis in working populations); cognitive stimulation and proteins in a random sample of 2261 participants from one cohort study; and proteins and dementia risk in 13 656 participants from two cohort studies.
Main outcome measures: Cognitive stimulation was measured at baseline using standard questionnaire instruments on active versus passive jobs and at baseline and over time using a job exposure matrix indicator. 4953 proteins in plasma samples were scanned. Follow-up of incident dementia varied between 13.7 to 30.1 years depending on the cohort. People with dementia were identified through linked electronic health records and repeated clinical examinations.
Results: During 1.8 million person years at risk, 1143 people with dementia were recorded. The risk of dementia was found to be lower for participants with high compared with low cognitive stimulation at work (crude incidence of dementia per 10 000 person years 4.8 in the high stimulation group and 7.3 in the low stimulation group, age and sex adjusted hazard ratio 0.77, 95% confidence interval 0.65 to 0.92, heterogeneity in cohort specific estimates I2=0%, P=0.99). This association was robust to additional adjustment for education, risk factors for dementia in adulthood (smoking, heavy alcohol consumption, physical inactivity, job strain, obesity, hypertension, and prevalent diabetes at baseline), and cardiometabolic diseases (diabetes, coronary heart disease, stroke) before dementia diagnosis (fully adjusted hazard ratio 0.82, 95% confidence interval 0.68 to 0.98). The risk of dementia was also observed during the first 10 years of follow-up (hazard ratio 0.60, 95% confidence interval 0.37 to 0.95) and from year 10 onwards (0.79, 0.66 to 0.95) and replicated using a repeated job exposure matrix indicator of cognitive stimulation (hazard ratio per 1 standard deviation increase 0.77, 95% confidence interval 0.69 to 0.86). In analysis controlling for multiple testing, higher cognitive stimulation at work was associated with lower levels of proteins that inhibit central nervous system axonogenesis and synaptogenesis: slit homologue 2 (SLIT2, fully adjusted β -0.34, P<0.001), carbohydrate sulfotransferase 12 (CHSTC, fully adjusted β -0.33, P<0.001), and peptidyl-glycine α-amidating monooxygenase (AMD, fully adjusted β -0.32, P<0.001). These proteins were associated with increased dementia risk, with the fully adjusted hazard ratio per 1 SD being 1.16 (95% confidence interval 1.05 to 1.28) for SLIT2, 1.13 (1.00 to 1.27) for CHSTC, and 1.04 (0.97 to 1.13) for AMD.
Conclusions: The risk of dementia in old age was found to be lower in people with cognitively stimulating jobs than in those with non-stimulating jobs. The findings that cognitive stimulation is associated with lower levels of plasma proteins that potentially inhibit axonogenesis and synaptogenesis and increase the risk of dementia might provide clues to underlying biological mechanisms.
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General Disclaimer: Please note that the opinions expressed here are those of Professor Giovannoni and do not necessarily reflect the positions of the Barts and The London School of Medicine and Dentistry nor Barts Health NHS Trust and are not meant to be interpreted as personal clinical advice.
I found the blend of everyday experience to physiological objectivity “stimulating”, and something (perhaps) I had observed with my parents. As a Psychologist (amateur first and then licensed, trained and professional), it was obvious to me the automatic nature of some people’s minds- how they automatically perceive and react the same way in different situations. That is fine to a point, but when it is done so automatically without consideration of alternatives, I wondered, is the brain really working? So my parents were not deep thinkers and even resisted the invitation to look at things in more detail, for fear they might be wrong about some far reaching decisions they had made in their lifetimes. So I have often wondered, is this automatic “wiring”, in some, another potential factor behind dementia? My father led a more healthy lifestyle but succumbed to Alzheimer’s type dementia. My mother was less “healthy” and succumbed to dementia brought about by high blood pressure, etc. Both were very cruel endings (in their early 80’s) and I have always hoped that perhaps I would not follow in their footsteps. My mother would be easier not to follow, my father, no so much. But clearly, even though a smart guy, he was done with thinking and preferred fishing.