Feb. 2, 2023 -- A new study suggests that following a healthy lifestyle is linked to slower memory decline in older adults, even in people with the apolipoprotein E4 (APOE4) gene, one of the strongest known risk factors for Alzheimer’s disease and related dementias.
A team of investigators in China analyzed 10-year data on over 29,000 older adults with an average age of 72 years. Of these, a fifth were carriers of the APOE4 gene.
The investigators created a healthy lifestyle score by combining how much participants engaged in six activities: healthy diet, regular exercise, active social contact, cognitive activity, nonsmoking, and avoiding alcohol. Participants were grouped into having "favorable," "average," and "unfavorable" lifestyles.
After adjusting for health, economic, and social factors, the researchers found that each individual healthy behavior was associated with a slower-than-average decline in memory during the decade, with a healthy diet emerging as the strongest deterrent, followed by cognitive activity and then physical exercise.
Those with "favorable" or "average" lifestyle showed slower memory decline, regardless of whether or not they had the APOE4 gene.
"A healthy lifestyle is associated with slower memory decline, even in the presence of the APOE4 allele," wrote Jianping Jia, MD, PhD, of the Innovation Center for Neurological Disorders and Department of Neurology, Xuan Wu Hospital, Capital Medical University in Beijing, China, and co-authors.
"This study might offer important information to protect older adults against memory decline," they wrote.
The study was published online Jan. 25 in the BMJ.
Memory "continuously declines as people age," but age-related memory decline doesn’t necessarily mean the person is developing dementia, according to the authors.
Factors affecting memory include aging, APOE4 genotype, chronic diseases, and lifestyle patterns. In particular, the role of lifestyle has been "receiving increasing attention" because, unlike a person’s genes or certain health conditions, lifestyle can be changed.
The researchers wanted to understand the role of a healthy lifestyle in possibly slowing memory decline, including in people with the APOE4 genotype. So they drew on data from the China Cognition and Ageing Study, which began in 2009 and ended in 2019.
At baseline, those in the study who were considered "cognitively normal" completed tests of cognition and memory and also provided information about their lifestyle, health, and economic and social factors. They were then reassessed in 2012, 2014, 2016, and at the conclusion of the study. The long follow-up period allowed for evaluation of individual lifestyle factors on memory function over time.
"Lifestyle" consisted of six factors:
- Physical exercise (weekly frequency and total time)
- Smoking status (current smoker, former smoker, or never smoked)
- Alcohol use (never drank, drank occasionally, low-to-excess drinking, and heavy drinking)
- Diet (daily intake of 12 food items: fruits, vegetables, fish, meat, dairy products, salt, oil, eggs, cereals, legumes, nuts, tea)
- Cognitive activity (writing, reading, playing cards, mahjong, other games)
- Social contact (participating in meetings, attending parties, visiting friends/relatives, traveling, chatting online)
The people's lifestyle was scored based on the number of healthy factors they engaged in, with "favorable" lifestyle consisting of four to six healthy factors, "average" lifestyle consisting of two to three healthy factors, and "unfavorable" lifestyle consisting of one to two healthy factors.
Public Health Implications
During the 10-year period, 7,164 people in the study died while 3,567 discontinued participation.
Compared with the group that had unfavorable lifestyles, memory decline in the favorable lifestyle group was 0.28 points slower over the decade-long study, and memory decline in the average group was 0.16 points lower.
Those with favorable or average lifestyle were almost 90% and 30% respectively less likely to develop dementia or mild cognitive impairment, compared to those with an unfavorable lifestyle.
The authors noted some limitations in their findings. For one, the study was observational, meaning that we don’t know whether the healthy lifestyle actually caused slower memory decline, or whether the association might be due to something else.
Still, the findings "might offer important information for public health to protect older adults against memory decline," especially since the study "provides evidence that these effects also include individuals with the APOE4 allele," the study authors said.
'Important and Encouraging' Findings
Severine Sabia, PhD, a senior researcher at the Université Paris Cité, INSERM Institut National de la Santé et de la Recherche Medicalé in France, called the findings "important and encouraging."
That said, Sabia, who is also the co-author of an accompanying editorial, notes that "there remain important research questions that need to be investigated in order to identify key behaviors, which combination [of behaviors], the cut-off of risk, and when to intervene."