A healthy lifestyle, in particular a healthy diet, is associated with slower memory decline, according to a decade-long study.
Even for carriers of the apolipoprotein E (APOE) gene - the strongest known risk factor for Alzheimer's disease and related dementias - a healthy lifestyle was found to slow memory loss.
Memory continuously declines as people age, but evidence from previous studies has been insufficient to assess the effect of a healthy lifestyle on memory in later life.
Chinese researchers analysed data from 29,000 adults aged at least 60 years (average age 72; 49 per cent women) with normal cognitive function who were part of the China Cognition and Aging Study.
At the start of the study in 2009, memory function was measured using the Auditory Verbal Learning test (AVLT) and participants were tested for the APOE gene (20 per cent were found to be carriers).
Follow-up assessments were then conducted over the next 10 years in 2012, 2014, 2016, and 2019.
A healthy lifestyle score combining six factors was then calculated: healthy diet, regular exercise, active social contact (eg. seeing friends and family), cognitive activity (eg. writing, reading, playing mahjong), non-smoking, and never drinking alcohol.
Based on their score, ranging from 0 to 6, participants were put into favourable (4 to 6 healthy factors), average (2 to 3 healthy factors), or unfavourable (0 to 1 healthy factors) lifestyle groups and into APOE carrier and non-carrier groups.
After accounting for a range of other health, economic and social factors, the researchers found that each individual healthy behaviour was associated with a slower than average decline in memory over 10 years.
A healthy diet had the strongest effect on slowing memory decline, followed by cognitive activity and then physical exercise.
Participants with the APOE gene with favourable and average lifestyles also experienced a slower rate of memory decline than those with an unfavourable lifestyle.
Those with favourable or average lifestyles were also less likely to develop dementia or mild cognitive impairment.
This is an observational study so can't establish cause and the researchers acknowledge some limitations, such as the potential for measurement errors due to self-reporting of lifestyle factors, and the possibility of selection bias, as some participants did not return for follow-up evaluations.
However, the researchers say their results provide strong evidence that adherence to a healthy lifestyle with a combination of positive behaviours is associated with a slower rate of memory decline, even for people who are genetically susceptible to memory decline.
They suggest a similar approach that led to a substantial reduction in cardiovascular disease should be taken with dementia prevention, "identifying not only the factors that matter most but also the threshold at which they matter, and the age when intervention is likely to be most effective."
The report was published in The BMJ.
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