Living a healthy lifestyle could slow memory decline

A good memory is essential to function well in daily life. As we get older, most of us will continue to have a good memory. Our general knowledge and skills are normally maintained throughout life and may even improve in old age. But the memory of specific events, called episodic memory, is more susceptible to aging, which can decrease the quality of life and productivity at work. Memory loss that occurs in older people is mostly mild, and can be reversed or stabilized rather than progressing to a pathological condition. Preventing and slowing down age-related memory decline is therefore very important for elderly people.

Studies indicate that several factors can affect memory, including the aging process, apolipoprotein E ε4 (APOE4) genotype, chronic diseases, and lifestyle habits. Since lifestyle habits are a modifiable factor, it has caught the attention of public health authorities since relatively easy changes can considerably improve both general and cognitive health.

A prospective longitudinal study recently attempted to identify the optimal lifestyle that would protect elderly people from memory decline. The study was carried out among participants of the China Cognition and Aging Study cohort, aged 60 or over, from 12 provinces of China. The 29,072 participants had an average age of 72.2 years at enrollment and had no mild cognitive impairment or dementia at the start of the 10-year study. About a fifth (20.4%) of the participants carried the APOE4 allele, a genetic risk factor for Alzheimer’s disease and other dementias.

Information about participants’ lifestyles was collected using detailed questionnaires at the beginning of the study and on other occasions in subsequent years. Six modifiable lifestyle factors were assessed: exercise, diet, alcohol consumption, smoking, cognitive activity and social contact (see Table 1).

Table 1. Criteria selected for a healthy lifestyle (Jia et al., 2023)

Factor	Parameters	Healthy lifestyle factors selected
Physical exercice	Frequency, intensity, duration	≥ 150 min of moderate exercise or ≥ 75 min of intense exercise per week
Diet	Consumption of 12 types of food (fruits, vegetables, fish, meat, dairy products, salt, oil, eggs, grains, legumes, nuts, tea)	Daily consumption of at least 7 of the 12 types of food
Alcohol consumption	• Non-drinker • Low to high consumption (1-60 grams of alcohol per day) • Excessive consumption (> 60 g/day)	Non-drinker
Smoking	• Non-smoker (<100 cigarettes in their lifetime) • Ex-smoker (stopped for ≥ 3 years) • Smoker	Non-smoker or ex-smoker
Cognitive activity	Examples: writing, reading, card games, mah-jong and other games.	Participation in at least 2 activities per week
Social contact	Examples: meetings, parties, visits to friends or family, travel, online conversation.	Participation in at least 2 activities per week

Participants were categorized into three groups: “favourable” (4-6 factors of a healthy lifestyle), “average” (2-3 factors), or “unfavourable” (0-1 factors). Verbal episodic memory was assessed by the Auditory Verbal Learning Test (AVLT), which includes measures of immediate, very short-term (3 minutes), and long-term (30 minutes) free recall, and of long-term recognition (30 min).

During the ten years of the study, participants in the favourable lifestyle group had a slower memory decline than those in the unfavourable lifestyle group (0.028 AVLT points/year, 95% CI 0.023-0.032). Among participants carrying the APOE4 allele, those in the favourable lifestyle group also had a slower memory decline than those in the unfavourable lifestyle group (0.027 AVLT points/year, 95% CI 0.023-0.031). Having a healthy lifestyle would therefore be a factor that can help slow memory loss, both in carriers of the APOE4 allele and in non-carriers.

Contribution of each factor

The researchers also assessed the contribution to memory decline of each of the six factors associated with a healthy lifestyle. A healthy diet is the factor that had the greatest effect on memory (β=0.016, 95% CI 0.014-0.017), followed by the practice of cognitive activities (β=0.010, 95% CI 0.008-0.012), physical exercise (β=0.007, 95% CI 0.005-0.009), social contact (β=0.004, 95% CI 0.002-0.006), smoking (β=0.004, 95% CI 0.000-0.008), and alcohol consumption (β=0.002, 95% CI 0.000-0.004).

Cognitive decline and dementia

Compared to participants who had an “unfavourable” lifestyle, those who had a “favourable” lifestyle were 89% less at risk of developing mild cognitive impairment or dementia. For participants with the “average” lifestyle, the risk was 29% lower. Similar results were obtained among participants carrying the APOE4 allele.

The observational nature of the study does not make it possible to establish a causal link between lifestyle and memory decline. In addition, this study has certain limitations, because lifestyle was assessed using a self-declaration questionnaire. Moreover, a selection bias cannot be excluded since some participants stopped taking part in the study during the 10 years of follow-up. Nevertheless, it is a large study and of relatively long duration, which made it possible to properly assess certain aspects of memory over time. The authors believe that the study results are robust and strongly suggest that adopting a healthy lifestyle, including several supportive behaviours, may be associated with slower memory decline, even in people who are genetically at risk of developing dementia or major cognitive impairment.