Leveraging the vast breadth of people receiving care in the Veterans Health Administration (VHA), first author Dr. Edward Zamrini and his colleagues studied 649,605 military veterans ages 30–95 years.
These individuals had not received a diagnosis with ADRD and had performed an Exercise Treadmill Test (ETT) as part of their routine care.
The scientists analyzed these individuals’ charts for the diagnosis of ADRD over an average of 8.8 years.
Dr. Zamrini, principal author Prof. Qing Zeng-Teitler, and their colleagues compared ETT results and the incidence at which ADRD developed in these individuals.
Exercise tolerance tests help quantify fitness levels using a standard of measure called METs, or metabolic equivalence of task.
In this study, the authors divided participants into five groups based on the METs they could achieve from lowest to highest fitness: on average, about 3.8 to 11.7 METs.
For comparison, 1 MET is equivalent to sitting quietly, yoga requires 3.2 METsTrusted Source, and backpacking at 3.63 miles per hour would demand 11.6 METs.
The scientists found that less fit individuals were at the highest risk of experiencing ADRD. Conversely, highly fit people were the least likely to develop ADRD.
Dr. Zamrini, director of neurology at Irvine Clinical Research, adjunct professor of clinical research and leadership at George Washington University, and adjunct professor of neurology at the University of Utah, explained to Medical News Today:
“Our study found a strong, graded inverse association between cardiorespiratory fitness and reduction of risk of [Alzheimer’s Disease]. This means that the more fit a person is, the more likely that if they were to develop AD, they would develop it later.”
Specifically, the researchers found that, compared with the least fit participants, the fittest were 33% less likely to develop ADRD. Similarly, the second most fit group was 26% less likely to develop ADRD, the third most fit group was 20% less likely, and the fourth most fit was 13% less likely.
“There are two main factors that influence cardiorespiratory fitness: genetics and exercise. We cannot change our genetics,” he continued, “but we can improve our cardiorespiratory fitness through a sensible exercise program. Our study also demonstrates that we don’t have to become marathon runners to reduce our risk. Even small increases in cardiorespiratory fitness can help!”
Dr. Scott Kaiser, a board certified geriatrician and director of geriatric cognitive health for the Pacific Brain Health Center at Pacific Neuroscience Institute in Santa Monica, CA, elaborated for MNT:
“You cannot prove that it was the low fitness that caused dementia. But, that said, the association was so clear, not just in the strength of the association but in the nature of the association. The way it so neatly correlated with rising fitness levels lowering dementia risk. It’s a very convincing association.”
“There are many other studies that have looked prospectively to affirm this link between physical fitness and risk of dementia and confirm that regular and recommended exercise can reduce [a person’s] risk of developing dementia,” continued Dr. Kaiser.
“So, studies like the [worldwide] FINGER study, out of Finland, where they are actually looking prospectively at populations over time — there is just mounting evidence […] that if you want to reduce your risk of dementia and maintain a healthy brain, you should exercise regularly and pursue other activities to improve your cardiorespiratory fitness.”
What’s the buzz?
What do these results mean? Dr. Zamrini elaborates:
“My advice to everyone concerned about their risk of [Alzheimer’s disease] is ‘live as healthy a lifestyle as you can manage.’ There are several lifestyle measures considered beneficial. These include exercise, diet, adequate sleep, and staying mentally active and socially engaged. The strongest evidence is for exercise.”
MNT asked Dr. Kaiser if ethnic or socioeconomic factors have a part in the development of dementia. Dr. Kaiser explained:
“When you talk about ethnic and socioeconomic demographic factors, the reality we are facing right now is that the research shows that older Latinos are about 1.5 times as likely as older white people to develop [Alzheimer’s disease].”
“And African Americans are twice as likely,” he continued, “so there are real equity issues at play here. It’s also a disease more common in women. So, getting to the root cause of why these differences exist and being able to do something about it is really, I think, one of the most important challenges we collectively face going forward. This is a big problem. I truly believe it can be solved.”
Limitations and further questions
MNT asked Dr. Zamrini if there were any limitations to the interpretation of the study results. He observed:Set featured image
“This is an epidemiologic study. Such studies do not prove cause and effect. However, the strength of epidemiologic studies is in the number of subjects studied. The large number in our study and the adjustments we made for co-morbidities strengthen our findings.”
“Our study was performed reviewing veterans’ (anonymized) data. Thus, the study may not be fully generalizable to the general population.”
On the topic of sex differences in dementia, Dr. Zamrini explained that “Because of the large dataset, even though the proportion of women is low (5.7%), the number of women studied is 36,881, which is still a large number, and we did not find a substantial difference in results between men and women.”
What to do?
MNT queried Dr. Scott Kaiser about what modifiable risk factors are important in Alzheimer’s. Dr. Kaiser noted that the Lancet Commission 2020 report on Dementia prevention, intervention, and care describes 12 modifiable risk factors linked to 40% of cases of dementia worldwide.
“If they have more genetic risk, my patients need to focus on their cardiorespiratory fitness as part of their overall brain-healthy lifestyle — meaning:
- keeping physically fit
- eating a healthy, balanced diet rich in fruits and vegetables
- getting a good nights’ sleep
- having meaningful relationships
- maintaining a strong sense of social connectedness
- avoiding excess alcohol
- not smoking
- having opportunities to restore and reduce stress through meditation and other forms of self-care.