A healthy lifestyle - in particular a nutritious diet - slows memory decline in older people, according to major new research.
The decade-long study of Chinese adults over the age of 60, published in The BMJ, showed that the benefits of healthy living were even seen in those with a gene making them genetically susceptible to Alzheimer’s disease.
Carriers of the apolipoprotein E (APOE) gene - the strongest known risk factor for Alzheimer’s and related dementia - saw a slowing in memory loss thanks to healthy living such as staying teetotal.
The Chinese research team said that memory continuously declines as people age, but evidence from existing studies is insufficient to assess the effect of a healthy lifestyle on memory in later life.
Given the many possible causes of memory decline, they explained that a combination of healthy behaviours might be needed for the best effect.
The researchers analysed data from 29,000 adults aged at least 60 with an average age of 72, almost half women, with normal cognitive function.
At the start of the study in 2009, memory function was measured using an 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 conducted in 2012, 2014, 2016, and 2019.
A healthy lifestyle score combining six factors - healthy diet, regular exercise, active social contact, cognitive activity such as reading and writing, non-smoking and never drinking alcohol - was then calculated.
Based on their score, ranging from zero to six, participants were put into favourable (four to six healthy factors), average (two or three), or unfavourable (one or zero) lifestyle groups and into APOE carrier and non-carrier groups.
After taking into account 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.
Study lead author Professor Jianping Jia said: “A healthy diet had the strongest effect on slowing memory decline, followed by cognitive activity and then physical exercise.
“Compared with the group that had unfavourable lifestyles, memory decline in the favourable lifestyle group was 0.28 points slower over 10 years based on a standardised score of the AVLT, and memory decline in the average lifestyle group was 0.16 points slower.
“Participants with the APOE gene with favourable and average lifestyles also experienced a slower rate of memory decline than those with an unfavourable lifestyle.
“What’s more, those with favourable or average lifestyles were almost 90 per cent and almost 30 per cent less likely to develop dementia or mild cognitive impairment relative to those with an unfavourable lifestyle, and the APOE group had similar results.”
He said the research was observational so can’t establish cause, but it was a large study with a long follow-up period, allowing for evaluation of individual lifestyle factors on memory function over time.
The researchers say their results provide “strong evidence” that sticking 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 further research could focus on the effects of a healthy lifestyle on memory decline across the entire lifespan, acknowledging that memory problems can also affect younger people.
Prof Jia, of the National Centre for Neurological Disorders in Beijing, added: “These results might offer important information for public health initiatives to protect older adults against memory decline.”
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