By Seema Gupta, MD, MSPH
Clinical Assistant Professor, Department of Family and Community Health, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV
SYNOPSIS: In a population-based, prospective cohort study of 29,000 Chinese adults, researchers found healthy lifestyle was associated with slower memory decline, even in the presence of the apolipoprotein E4 allele.
SOURCE: Jia J, Zhao T, Liu Z, et al. Association between healthy lifestyle and memory decline in older adults: 10-year, population based, prospective cohort study. BMJ 2023;380:e072691.
Americans are living longer in greater numbers than ever. In the United States, more than 10,000 people turn age 65 years daily.1 With an aging population also comes a heavier burden of chronic diseases, such as hypertension, heart disease, diabetes, arthritis, and dementia. Dementia is becoming one of the most challenging public health issues globally because of both a rising prevalence from aging of the population as well as the absence of a curative therapy.2 The global estimates of costs for dementia were approximately $958 billion in 2015, and are expected to reach $2.54 trillion in 2030, and $9.12 trillion by 2050.3
Age-related memory decline may not always be a prelude to dementia. Existing evidence suggests factors such as aging, the apolipoprotein E4 (APOE4) genotype, several chronic diseases, and lifestyle patterns may affect memory.4 Over the past several decades, clinical trials have consistently failed to identify any drugs that could cure dementia or even substantially modify the disease process. In contrast, a large body of epidemiological evidence suggests memory loss can be slowed or prevented by interventions targeting major modifiable risk and protective factors.5 However, it may be important to assess the effects of healthy lifestyle on memory decline in individuals with a higher genetic risk.
Jia et al conducted a population-based, prospective cohort study of 29,000 Chinese adults older than age 60 years with normal cognitive function. At baseline in 2009, memory function was measured using tests, and people were checked for the APOE gene, which is the strongest risk-factor gene for Alzheimer’s disease. Mean age of participants was about 72 years; 48.5% in the cohort were women, and 20.4% were APOE4 carriers. The subjects were followed for 10 years with periodic assessments. A healthy lifestyle score combining six factors was calculated, including physical exercise, diet, social contact, cognitive activity, smoking, and drinking alcohol. Based on their score, ranging from 0 to 6, participants were placed into lifestyle groups such as favorable (4-6 healthy factors), average (2-3 healthy factors), or unfavorable (0-1 healthy factors). Participants also were stratified by APOE genotype into APOE4 carriers and noncarriers.
Researchers found participants in the favorable and average groups showed slower memory decline per increased year of age (0.007 points/year; 95% CI, 0.005-0.009; P < 0.001 and 0.002 points/year; 95% CI, 0.000-0.003; P = 0.033 points higher, respectively) compared to those in the unfavorable group. Healthy diet produced the strongest protective effect on memory. Memory decline occurred faster in APOE4 carriers when compared with noncarriers (0.002 points/year; 95% CI, 0.001-0.003; P = 0.007). However, APOE4 carriers with favorable and average lifestyles showed slower memory decline (0.027 points/year; 95% CI, 0.023-0.031 and 0.014 points/year; 95% CI, 0.010-0.019, respectively) compared to those with unfavorable lifestyles. Findings in noncarriers were similar.
Researchers found those with favorable or average healthy lifestyles were almost 90% and 30%, respectively, less likely to develop dementia or mild cognitive impairment compared to those with an unfavorable lifestyle.
COMMENTARY
The fact that healthy lifestyle behaviors can help protect older patients against memory decline is an important finding. With significant extensions in life expectancy over the past century, we find ourselves at the crossroads where the world is aging faster than anytime in human history. Concurrently, we have not discovered a treatment for dementia, which arguably is the most crippling and disabling disease of old age. We know the risks of cognitive decline and dementia probably are determined by multiple factors. Therefore, prevention is important, and the Jia et al study provides evidence for specific lifestyle factors that may help protect against dementia.
Because these results do not help us figure out which ones among the six health behaviors included or what combination are the best targets for dementia prevention, we should be recommending for all of these: exercise regularly, eat a healthy diet, maintain plentiful social contact, engage in cognitive improvement activities, and avoid smoking and alcohol. There is no set time in one’s life course to focus on prevention efforts. For that, we should be able to individualize recommendations based on each patient’s risk. When it comes to prevention, earlier is better.
REFERENCES
1. Centers for Disease Control and Prevention. Healthy aging: Promoting well-being in older adults. Page last reviewed Feb. 28, 2018.
2. Alzheimer’s Association. 2015 Alzheimer’s disease facts and figures. Alzheimers Dement 2015;11:332-384.
3. Jia J, Wei C, Chen S, et al. The cost of Alzheimer’s disease in China and re-estimation of costs worldwide. Alzheimers Dement 2018;14:483-491.
4. Rosenich E, Bransby L, Yassi N, et al. Differential effects of APOE and modifiable risk factors on hippocampal volume loss and memory decline in Abeta- and Abeta+ older adults. Neurology 2022;98:e1704-e1715.
5. Livingston G, Sommerlad A, Orgeta V, et al. Dementia prevention, intervention, and care. Lancet 2017;390:2673-2734.
In a population-based, prospective cohort study of 29,000 Chinese adults, researchers found healthy lifestyle was associated with slower memory decline, even in the presence of the apolipoprotein E4 allele.
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