Summary: Adults over 80 who maintained a healthy lifestyle, including exercise and diet, had a lower risk of cognitive decline, even if they had genetic risk factors for dementia.
A new analysis of adults aged 80 years and older shows that a healthier lifestyle is associated with a lower risk of cognitive impairment, and that this link does not depend on whether a person carries a particular form of the gene APOE.
Xurui Jin of Duke Kunshan University in Jiangsu, China, and colleagues present these findings in the open-access journal PLOS Medicine.
The APOE gene comes in several different forms, and people with a form known as APOE ε4 have an increased risk of cognitive impairment and Alzheimer’s disease. Previous research has also linked cognitive function to lifestyle factors, such as smoking, exercise, and diet. However, it has been unclear whether the benefits of a healthy lifestyle are affected by APOE ε4, particularly for adults over 80 years of age.
To clarify the relationship between APOE ε4 and lifestyle, Jin and colleagues examined data from 6,160 adults aged 80 or older who had participated in a larger, ongoing study known as the Chinese Longitudinal Healthy Longevity Survey. The researchers statistically analyzed the data to investigate links between APOE ε4, lifestyle, and cognition. They also accounted for sociodemographics and other factors that could impact cognition.
The analysis confirmed that participants with healthy lifestyles or intermediately healthy lifestyles were significantly less likely to have cognitive impairment than those with an unhealthy lifestyle, by 55 and 28 percent, respectively. In addition, participants with APOE ε4 were 17 percent more likely to have cognitive impairment than those with other forms of APOE.
A previous study suggested that in individuals at low and intermediate genetic risk, favorable lifestyle profiles are related to a lower risk of dementia compared to unfavorable profiles. But these protective associations were not found in those at high genetic risk.
However, the investigation showed the link between lifestyle and cognitive impairment did not vary significantly based on APOE ε4 status which represented the genetic dementia risk. This suggests that maintaining a healthier lifestyle could be important for maintaining cognitive function in adults over 80 years of age, regardless of genetic risk.
This cross-sectional study emphasized the importance of a healthy lifestyle on cognitive health. While further research will be needed to validate these findings among different population, this study could help inform efforts to boost cognitive function for the oldest of adults.
In the next step, the team will explore this association using the AD polygenetic risk score (AD-PRS) and explore the interactive relationship between AD-PRS and lifestyle on cognition with the longitudinal data.
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Source: PLOS Contact: Lijing Yan – PLOS Image: The image is in the public domain
Association of APOE ε4 genotype and lifestyle with cognitive function among Chinese adults aged 80 years and older: A cross-sectional study
Apolipoprotein E (APOE) ε4 is the single most important genetic risk factor for cognitive impairment and Alzheimer disease (AD), while lifestyle factors such as smoking, drinking, diet, and physical activity also have impact on cognition. The goal of the study is to investigate whether the association between lifestyle and cognition varies by APOE genotype among the oldest old.
Methods and findings
We used the cross-sectional data including 6,160 oldest old (aged 80 years old or older) from the genetic substudy of the Chinese Longitudinal Healthy Longevity Survey (CLHLS) which is a national wide cohort study that began in 1998 with follow-up surveys every 2–3 years. Cognitive impairment was defined as a Mini-Mental State Examination (MMSE) score less than 18.
Healthy lifestyle profile was classified into 3 groups by a composite measure including smoking, alcohol consumption, dietary pattern, physical activity, and body weight. APOE genotype was categorized as APOE ε4 carriers versus noncarriers. We examined the associations of cognitive impairment with lifestyle profile and APOE genotype using multivariable logistic regressions, controlling for age, sex, education, marital status, residence, disability, and numbers of chronic conditions.
The mean age of our study sample was 90.1 (standard deviation [SD], 7.2) years (range 80–113); 57.6% were women, and 17.5% were APOE ε4 carriers. The mean MMSE score was 21.4 (SD: 9.2), and 25.0% had cognitive impairment. Compared with those with an unhealthy lifestyle, participants with intermediate and healthy lifestyle profiles were associated with 28% (95% confidence interval [CI]: 16%–38%, P < 0.001) and 55% (95% CI: 44%–64%, P < 0.001) lower adjusted odds of cognitive impairment. Carrying the APOE ε4 allele was associated with 17% higher odds (95% CI: 1%–31%, P = 0.042) of being cognitively impaired in the adjusted model.
The association between lifestyle profiles and cognitive function did not vary significantly by APOE ε4 genotype (noncarriers: 0.47 [0.37–0.60] healthy versus unhealthy; carriers: 0.33 [0.18–0.58], P for interaction = 0.30). The main limitation was the lifestyle measurements were self-reported and were nonspecific. Generalizability of the findings is another limitation because the study sample was from the oldest old in China, with unique characteristics such as low body weight compared to populations in high-income countries.
In this study, we observed that healthier lifestyle was associated with better cognitive function among the oldest old regardless of APOE genotype. Our findings may inform the cognitive outlook for those oldest old with high genetic risk of cognitive impairment.