People with intellectually stimulating jobs are slightly less likely to develop dementia when they are older 鈥� and we may have some new clues about how a person鈥檚 lifestyle physically protects their brain.
The finding adds support to the idea that people with more active intellectual lives are somehow buffered against dementia through a 鈥渃ognitive reserve鈥�, but it is still unclear if we can reduce dementia risk by changing our lifestyles.
The idea of cognitive reserve stems from findings that people are less likely to develop dementia if they score higher on IQ tests in childhood or if they have active intellectual lives as they age. It has led to advice that people should try to maintain their brain health as they get older through mentally taxing hobbies such as crossword puzzles or 鈥渂rain training鈥� games, but there is little supporting evidence from randomised trials.
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at University College London and his colleagues wondered if any effect would be clearer when taking into consideration mental stimulation from people鈥檚 jobs, because we tend to spend more time at work than on hobbies.
His team analysed existing results from seven studies done in the UK and other countries that looked at over 100,000 people, recording their occupation and whether they developed dementia over the following 17 years, on average.
People in mentally stimulating professions had a lower risk of dementia than those with other jobs, although the difference was small. It would translate to dementia being diagnosed 1.7 years later if they had had a mentally taxing job, for people around the age of 80, or 2.5 fewer diagnosed cases per 10,000 鈥減erson-years鈥�, a measure that combines the number of people with how many years they were tracked.
The group also looked at levels of nearly 5000 biochemicals in people鈥檚 blood, which had been measured in two studies. Both mentally demanding jobs and lower dementia risk were linked with lower levels of three potentially harmful compounds.聽Previous research in animals and cells grown in the lab suggests these compounds either block formation of new synapses 鈥� the connections between cells聽鈥� or brain cell outgrowths called axons. This could explain how mental activity protects against dementia, if indeed it does, says Kivim盲ki.
The proteins could be targeted by drugs to reduce dementia risk, says Kivim盲ki. 鈥淗owever, we need more information about causality: do the proteins really affect the brain or are they only markers of other factors that affect the brain?鈥�
BMJ
