Healthy Living Tied to a Longer Life and Dementia-Free Old Age

A healthy diet, physical activity, and cognitive training help extend life expectancy — and those extra years are more likely to be dementia-free — new research suggests.

An analysis of nearly 2500 participants in the Chicago Health and Aging Project (CHAP) showed those who had a healthy diet, got plenty of physical activity, and participated in cognitive exercises lived longer than those following a less healthy lifestyle.

In addition, the number of years living with dementia was almost halved among participants with the healthiest lifestyle versus those with the least healthy lifestyle.

"This study supports the current literature regarding lifestyle and dementia; that is, a healthy lifestyle may contribute to lowering the risk of Alzheimer's dementia," Klodian Dhana, MD, PhD, assistant professor, Department of Internal Medicine, Division of Geriatrics and Palliative Medicine, Rush University Medical Center, Chicago, Illinois, told Medscape Medical News.

The study was published online April 13 in the British Medical Journal.

An Important Question

Past research has shown adhering to a healthy lifestyle may extend life expectancy, but older age is associated with a higher risk of dementia. What hasn't been clear is whether extending life just increases the number of years spent with dementia, the current investigators note.

The new study was created to address that question, they add. It used data from 2449 participants (mean age, 76 years) in CHAP, a population-based study that began in 1993 and was designed to assess risk factors of Alzheimer's dementia in the general population.

Researchers obtained data on lifestyle factors, medical history, genotyping, and neurocognitive tests through detailed questionnaires and biospecimen collection. The neurocognitive tests were administered every 3 years up to six times throughout the study.

Diet quality was determined using the Mediterranean-DASH Diet Intervention for Neurodegenerative Delay (MIND), which is rich in whole grains, green leafy vegetables, and berries, and low in fast/fried food and red meats. Cognitive activities were evaluated by reported participation in such tasks as reading, playing card games, and doing crossword puzzles.

Investigators also considered time spent in moderate or vigorous activities, including walking, gardening, bicycling, and swimming; and recorded smoking status and alcohol consumption.

For each lifestyle factor, participants got a score of 1 if they met criteria for healthy or low risk and 0 if they didn't. Researchers summed the five scores for a final score ranging from 0 to 5, with higher scores indicating a healthier lifestyle.

A diagnosis of dementia was based on impairment in two or more functions on cognitive performance tests and a loss of cognitive function determined by a neurologist. An Alzheimer's dementia diagnosis was determined using standard criteria.

Researchers used a "multistate" life expectancy analysis that considers associations when subjects move from one health state to another; in this case, dementia-free to dementia, dementia-free to mortality, and dementia to mortality. This provides estimates of years lived with and without dementia.

In addition, adjustments were made for age, race, marital status, education, apolipoprotein E status, comorbidities, and calendar cycle/cohort in which the lifestyle factors were assessed.

"Many Limitations"

Among study participants, 2110 were free of Alzheimer's dementia at baseline and 339 had prevalent Alzheimer's dementia.

Participants had about 12.5 years of schooling; and 57% of women and 56% of men were Black. Participants with healthy lifestyle factors were a little younger, less likely to be Black, and had more years of education than those with a less healthy lifestyle.

Results showed life expectancy at age 65 was 24.2 years for women with the healthiest lifestyles (score of 4 or 5) and 21.1 years for those with the least healthy lifestyles (score of 0 or 1). For men, life expectancy at age 65 was 23.1 and 17.4 years, respectively.

Extra years of life did not translate into more years living with dementia. The number of years living with dementia was 2.6 years for women with the healthiest lifestyle versus 4.1 years for those with the least healthy lifestyle. For men, it was 1.4 years versus 2.1 years, respectively.

A sensitivity analysis showed associations between lifestyle, Alzheimer's dementia, and mortality were similar for White and Black participants.

Overall, the results "may help the communication between doctors and patients regarding lifestyle and dementia," Dhana said.

However, he noted the study is observational and has "many limitations."

First, adherence to lifestyle factors was not updated during the follow-up. Also, the proportion of participants with an unhealthy lifestyle was potentially underestimated as individuals in poor health are less likely to participate in studies such as this one, Dhana said.

As well, assessments of lifestyle factors were based on self-report and could be prone to measurement error, although the questionnaires were validated.

Important Implications?

In an accompanying editorial, HwaJung Choi, PhD, research assistant professor, Department of Internal Medicine and Department of Health Management and Policy, University of Michigan, Ann Arbor, notes the findings have important implications for the well-being of aging populations and for health policies.

"Alzheimer's disease and other dementias are among the most expensive health conditions both economically and socially, having a profound impact on those with dementia, their families, and wider society," Choi writes.

She notes the total direct cost of care for the approximately 6 million US adults with dementia was an estimated $355 billion in 2021. In addition, research shows more than 11 million family members and other caregivers provided about 15 billion hours of unpaid help in 2020.

"The development and implementation of intervention programs to reduce the risk of Alzheimer's disease and other dementias is critically important in global efforts to reduce pressure on stressed healthcare systems, healthcare workers, and both paid and unpaid carers," Choi writes.

"Promoting greater engagement in healthy lifestyles may increase dementia-free life-years — by delaying the onset of dementia without extending life-years spent with dementia," she adds.

The study was funded by the National Institutes on Aging of the National Institute of Health. Dhana and Choi have reported no relevant financial relationships.

BMJ. Published online April 13, 2022. Full text, Editorial

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