Even light-intensity exercise might reduce dementia risk

Someone walking along a road with the city in the background.
A recent study finds further links between physical activity and dementia risk. David Madison/Getty Images
  • Dementia affects millions of older people, and researchers expect the number of people with dementia in the United States to nearly triple by 2060.
  • There is no known cure for dementia. However, some behavioral changes may reduce the risk.
  • A recent study found an association between light-intensity exercise and reduced risk of dementia in older adults.
  • Scientists need to do more work to determine whether the association is causal.

In a new study, researchers have identified an association between light-intensity physical exercise in older adults and a reduced risk of dementia.

The study, which appears in JAMA Open Network, lays the ground for further research to determine whether light-intensity physical exercise causes the reduction in risk.

Dementia

According to the Centers for Disease Control and Prevention (CDC), dementia is a general term for a range of conditions characterized by cognitive impairment.

Dementia typically affects people over the age of 65, although it is not an expected part of aging. The most common type of dementia is Alzheimer’s disease.

Alzheimer’s disease is a neurodegenerative illness, meaning it gets worse over time.

According to the World Health Organization (WHO), during the early stages of dementia, someone may become forgetful, lose track of time, or not remember a familiar person. In its late stages, dementia can significantly reduce an individual’s awareness of the world.

There is no known cure for neurodegenerative dementia. Instead, doctors focus on reducing the symptoms and promoting lifestyle changes that might reduce the risk of dementia developing.

Over 60,000 participants

In the present study, researchers investigated whether there was an association between doing light-intensity physical exercise and a reduced risk of developing dementia in older adults.

The study involved 62,286 participants who were 65 years or older, did not have a dementia diagnosis, and had medical records in the Korean National Health Insurance Service database.

Researchers gathered data between January 2009 and December 2012 and tracked the participants until the end of December 2013. They completed data analysis from July 2020 to January 2021.

Women accounted for 60.4% of the participants, and the mean age was 73.2.

The participants recorded their level of physical activity at the beginning of the study period using a self-reported questionnaire. The researchers looked at the frequency, intensity, and duration of the exercise to determine how much energy expenditure was due to physical activity.

After a median follow-up period of 42 months, the researchers noted how many participants developed dementia.

Reduced risk of dementia

During the follow-up period, 6% of the participants developed dementia.

The researchers split participants into four groups depending on how active they were: inactive, insufficiently active, active, and highly active.

They found that insufficiently active participants had a 10% reduced risk of developing dementia compared with inactive participants.

Active participants had a 20% reduced risk, while highly active participants had a 28% reduced risk.

The findings remained the same even after accounting for age, sex, and incidence of stroke and other comorbidities.

Micro B Life spoke with Dr. Boyoung Joung, a professor of internal medicine at Yonsei University College of Medicine in Seoul, Republic of Korea, and the study’s corresponding author. He said that “[i]n our study, we would like to emphasize that even light-intensity physical activity, as opposed to total sedentary behavior, could lead to a reduction in risk of dementia.”

“Therefore, older adults who cannot perform activity beyond moderate-intensity physical activity, due to […] frailty or comorbidities, could benefit from light-intensity physical activity.”

“There are some reports that light-intensity physical activity is associated with metabolism, and this vascular, cellular, and metabolic change by light-intensity physical activity could be beneficial in reducing dementia risk.”

– Dr. Boyoung

Causation?

Prof. Paul M. Matthews — director of the UK Dementia Research Institute Centre at Imperial College London in the United Kingdom — explained to MBL that “[t]his is a well-conducted retrospective epidemiological study. The results are consistent with prior similar studies in other populations, and with the conclusions of the prospective, randomized FINGER Trial.”

“However, as an observational study, it can only be used to suggest that light physical activity may reduce the risk of dementia. [T]he results cannot be interpreted directly as evidence that starting light physical activity will reduce the risk of dementia,” cautioned Prof. Matthews, who was not involved in the study.

MBL also spoke with Prof. John Gallacher, director of Dementias Platform UK, at the University of Oxford in the U.K., who was not involved in the study. He agreed with Prof. Matthews, explaining that the findings were significant, but the question of causation was key.

“The idea that physical activity reduces the risk of dementia is entirely plausible, and these findings add to a growing body of evidence supporting this idea. The problem is reverse causation — that is, that people with dementia exercise less.”

– Prof. John Gallacher

“This study goes some way to addressing this by looking at incident events and dropping subjects with incident dementia in the first 2 years of follow-up. The dose-response curves are impressive,” he continued.

Prof. Gallacher said that “[p]ossible mechanisms [for the association] include improved vascular health and improved immunological function. These mechanisms are likely to be interrelated and not independent of each other.”

Prof. Matthews also believed that some variables that the researchers did not factor in could account for the results. However, biological mechanisms were also possible.

“Amongst other factors, differences in relative frailty, social integration, and family background were not able to be controlled in the study. A trivial explanation for the results is that these types of uncontrolled variables accounted for differences.”

“Alternatively, there is biological evidence that physical activity could increase levels of factors that protect neurons, improve metabolism to reduce rates of ‘senescence’ — cell aging — and brain plasticity,” said Prof. Matthews.

Different dementias?

Speaking with MBL, Prof. Tara Spires-Jones — personal chair of neurodegeneration and the deputy director of the Centre for Discovery Brain Sciences at the University of Edinburgh, U.K. — said, “[t]he study of modifiable risk factors for dementia is very important as best estimates suggest over one-third of dementia cases are preventable by modifying lifestyle.”

“This study by Yoon and colleagues observes an association between exercise and reduced risk of dementia. While this type of study cannot prove that the exercise was the cause of reduced risk, the data are robust and come from a large number of people,” said Prof. Spires-Jones, who was not involved in the study.

“This study is important because it suggests that even light exercise may lower dementia risk. This work could be built upon by doing formal trials of the preventative power of exercise, some of which are currently ongoing around the world.”

Continuing, Prof. Spires-Jones told MBL that “This study shows exercise was associated with preventing Alzheimer’s disease more than vascular dementia, which is consistent with previous data. We don’t know why this is the case, but it is possible that other risk factors like high blood pressure and diabetes are more influential in vascular disease risk than exercise.”

Dr. Boyoung agreed, noting that “[o]ther modifiable risk factors, such as hypertension and diabetes, could play an important role in vascular dementia. That’s why physical activity was more protective against Alzheimer’s disease than against vascular dementia.”

Prof. Gallacher explained that “[t]he absence of effect for vascular dementia is inconsistent with the mechanisms described above. However, the analysis, in controlling for variables related to vascular disease — blood pressure, body-mass index, etc. — may well have adjusted-out effects on vascular dementia. A more detailed analysis would inform this.”

For Prof. Matthews, “[t]he genetic basis for [Alzheimer’s disease and vascular dementia] is distinct and the extent to which genes alone determine them differs. This suggests that modification of specific risk factors should have different effects on the two clinical outcomes.”

Future research

Dr. Boyoung said that further research with longer follow-up analysis and a more detailed overview of participant exercise levels would be valuable.

“As dementia has a long subclinical period, further studies with relatively longer follow-up duration are needed. Also, because patterns of physical activity could be changed during [the] follow-up period, studies considering this change of physical activity are warranted,” said Dr. Boyoung.

Prof. Gallacher also noted some ways researchers could develop the study.

“As dementia has a 10–15 year presymptomatic stage, the study could be improved by dropping subjects with incident dementia in the first 5 years of follow-up, but I suspect the study is too small for that.”

“So what is needed is a larger study. Also, questionnaire responses are prone to error. A study using actigraphy to assess physical activity objectively would be an important next step.”

“All these arguments apart, the balance of risk is that exercise is good for you, and a little goes a long way!” concluded Prof. Gallacher. Prof. Spires-Jones agreed:

“The take-home message from this and similar research is that it is important to exercise to protect your brain as you age.”

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