Alzheimer’s disease: is diet key to dementia?

A new decade-long study of older adults in China has found that a healthy lifestyle, in particular a good diet, is associated with slower memory decline. Researchers say that even carriers of the apolipoprotein E (APOE) gene – the strongest known risk factor for Alzheimer’s disease and related dementia – do better cognitively by addressing lifestyle factors over a sustained period.

A large team of scientists, led by Professor Jianping Jia at Capital Medical University, Beijing, analysed data from 29,000 adults aged at least 60 years (average age 72; 49% 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% 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 (e.g. seeing friends and family), cognitive activity (e.g. 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.

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 (z 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 (0.027 and 0.014 points per year slower, respectively).

What’s more, those with favourable or average lifestyles were almost 90% and almost 30% less likely to develop dementia or mild cognitive impairment relative to those with an unfavourable lifestyle, and the APOE group had similar results.

‘These results might offer important information for public health initiatives to protect older adults against memory decline,’ the authors say, particularly given the limited treatment options available to managing dementia.