Illustration: Alzheimer's

 

By: Dr Stéphane Cohen*

The gradual loss of thinking skills such as memory, reasoning and psychomotor speed is a natural part of aging. However, studies such as the FINGER clinical trial have shown that it is possible to prevent cognitive decline through lifestyle improvements.

The impact of lifestyle factors on memory has been widely studied. However, previous research has typically focused on a single lifestyle factor, such as diet, physical activity, smoking, or drinking. It is important to understand the combined effect of multiple lifestyle factors on memory decline.

For this reason, Dr. Jianping Jia, Ph.D., a neurologist and professor at Capital Medical University, Beijing, China, and colleagues investigated the combined effects of six lifestyle factors on memory decline in a large study population over a 10-year period. period.

In an interview with Medical News Oil Dr. Jia said:

"Efficient strategies to protect against memory decline can benefit large numbers of older adults. Our results showed that adherence to a combination of healthy lifestyles was associated with slower memory decline in older adults, including those genetically susceptible to memory decline."

The results of the study appear in the BMJ.

Dr. Richard J. Caselli, professor of neurology at the Mayo Clinic, who was not involved in the study, described the study as "well done and generally supportive of the results of studies such as the FINGER study, this time in a Chinese population. ”

Large study with a decade of follow-up
The researchers recruited 29,072 study participants from northern, southern and western China aged 60 or older with typical cognitive functions. Their average age was 72.2 years and 51.5% were male.

Genetic testing at baseline showed that 20.43% of study participants carried the APOE ε4 gene, the strongest known risk factor for Alzheimer's disease and related dementias.

The researchers followed the participants at regular intervals over the next 10 years, in 2012, 2014, 2016 and 2019.

At baseline and at each follow-up, the researchers assessed participants' memory using the Auditory Verbal Learning Test (AVLT), which includes the measure of immediate recall, short recall without delay (3 min later), long recall without delay (30 min later), and recognition of long delays.

Six factors of a healthy lifestyle For this study, Dr. Jia and his colleagues used US guidelines and results from previous studies to define a healthy lifestyle. They identified six factors:

  1. a healthy diet – meeting the recommended intake of at least 7 of the 12 eligible foods (fruits, vegetables, fish, meat, dairy products, salt, oil, eggs, cereals, legumes, nuts and tea)
  2. regular physical exercise – at least 150 minutes of moderate-intensity activity or at least 75 minutes of vigorous-intensity activity per week
  3. Active social contact (attending meetings or parties, visiting friends or relatives, traveling and chatting online) – at least twice a week
  4. active cognitive activity (writing, reading, playing cards, mahjong and other games) – at least twice a week
  5. never smokes (participants who had smoked less than 100 cigarettes in their lifetime) or used to smoke (participants who had quit smoking at least 3 years before the study)
  6. never drank alcohol or drank occasionally

The researchers categorized the participants into groups based on their number of factors related to a healthy lifestyle:

  1. 0-1 healthy lifestyle factors = unfavorable lifestyle (6967 participants)
  2. 2-3 healthy lifestyle factors = average lifestyle (16,549 participants)
  3. 4-6 healthy lifestyle factors = favorable lifestyle (5556 participants)

A healthy lifestyle slows down memory decline

The average memory test scores of all participants declined steadily over the decade, consistent with how memory declines with age. However, the highest scores on memory tests were observed in the favorable lifestyle group and the lowest in the unfavorable lifestyle group, indicating that participants with a favorable lifestyle had a decline in memory. memory slower than those with an unfavorable lifestyle (by 0.028 point/year).

The results showed that a healthy diet had the strongest effect on memory, followed by active cognitive activity, regular physical exercise, active social contact, never having smoked or never have drunk.

This study did not identify the mechanisms responsible for modifying memory loss. However, the researchers speculated that they may include "reduced stroke risk, improved cognitive reserve, inhibition of oxidative stress and inflammation, and promotion of neurotrophic factors."

Dr. Caselli told MNT that the "results echo heart-healthy behaviors (diet, exercise, non-smoking in particular), with the addition of active social and cognitive activity, [and] cardiovascular health [ …] in turn is important for our cognitive health, so whether directly or indirectly [beneficial to memory], these results seem credible and consistent with other well-conducted studies.

Dorly JH Deeg, Ph.D., professor of epidemiology of aging at the University of Amsterdam Medical Center, who was not involved in the study, also praised the study for its sample. wide and varied population and the many analyzes supporting the results.

Healthy lifestyle vs genetic risk of Alzheimer's

The APOE ε4 allele, present in 20.43% of study participants, is correlated with earlier and more rapidly progressive memory decline and represents a major risk factor for Alzheimer's disease.

In this study, the researchers observed that a healthy lifestyle positively affected the memory of all participants, whether or not they carried the APOE ε4 allele.

“[W]e find that some people are discouraged upon finding out that they carry ε4 […] The results of this study will hopefully give these people hope that they can actively mitigate their genetic vulnerability” , said Dr. Caselli.


Limitations of the study and next steps

In their paper, Dr. Jia and his colleagues identify several study limitations, including that lifestyle factors were self-reported and therefore subject to measurement error. In addition, memory was assessed using a single neuropsychological test. They also acknowledge that the study design did not assess whether a healthy lifestyle began to affect memory before age 60.

Dr. Caselli told MNT that the possibility that some participants are in the preclinical stage of Alzheimer's disease cannot be ruled out. "Although this required a 10-year follow-up, the preclinical phase of Alzheimer's disease is closer to 20 years, so things like social and cognitive activity may already begin to decline in subtle ways before 'A person with the disease at the preclinical stage only develops overt symptoms and is diagnosed with MCI [mild cognitive impairment],' he said.

In comments to MNT, Dr. Deeg pointed out that the researchers "excluded a large number of participants (30% of eligible people)". In the study document, "[t]his is described as 'under 60, declined to participate, etc.' As a reviewer, I don't think that's a satisfying explanation,” she said.

Dr Deeg told MNT that the results of observational studies such as this "should be replicated in randomized controlled trials".

“Such trials have been done – usually with a single lifestyle factor, primarily physical activity. Unfortunately, the results are not unequivocal, and a recent JAMA article showed no effect,” she added. “So we have a long way to go to find out which intervention would work and why – and for that we need to know what the underlying mechanisms of the brain are."

In a related editorial to this study, Séverine Sabia, Ph.D., research professor at Paris Cité University in France, and Archana Singh-Manoux, Ph.D., research professor at University College London recommend that future research be focus on “identifying not only the factors that matter most, but also the threshold at which they matter and the age at which intervention is likely to be most effective. (ma-clinique)

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