Even a little exercise could significantly lower dementia risk

New research offers encouraging news for individuals concerned about dementia: even small amounts of physical activity may substantially reduce the risk of developing this devastating condition. A study published in the Journal of the American Medical Directors Association has found that engaging in a minimal amount of moderate to vigorous physical activity each week is linked to a significantly lower chance of dementia, even for older adults who are already frail. The findings suggest that incorporating just a few minutes of movement into one’s weekly routine can have a powerful protective effect on brain health.

Dementia is a growing global health challenge, affecting millions of people and their families. It is a leading cause of death, and currently, there is no cure. Dementia is not a single disease, but rather a group of conditions that affect cognitive abilities like memory, thinking, and problem-solving, to the point where it interferes with daily life. Scientists are working hard to understand how to prevent or delay dementia, and one promising area of investigation is physical activity.

Previous studies have indicated that being physically active can be beneficial for brain health and may lower dementia risk. However, it has been unclear exactly how much physical activity is needed to see these benefits, particularly for older adults who may find it difficult to be very active due to age-related frailty or other health issues. Frailty is a state of increased vulnerability to health problems, often seen in older adults, and is itself linked to a higher risk of dementia.

Researchers wanted to determine the minimum amount of moderate to vigorous physical activity needed to reduce dementia risk and to see if this benefit held true even for frail older adults. Understanding this “minimum dose” could help encourage more people, especially those who are less active or frail, to incorporate some movement into their lives for brain health benefits.

To investigate this question, researchers used data from a large study called the UK Biobank. This extensive project has collected health information from over 500,000 people in the United Kingdom, aged 40 to 69 at the time they joined the study between 2006 and 2010. The participants provided detailed information about their lifestyle, health, and underwent physical measurements.

A subset of these participants, over 100,000 individuals, agreed to wear a special device called an accelerometer on their wrist for up to seven days between 2013 and 2015. This device is like a sophisticated step counter, but it measures movement very precisely, allowing researchers to determine the intensity and duration of physical activity. The accelerometer data provided objective measurements of how much moderate to vigorous physical activity each person engaged in. Moderate to vigorous physical activity is defined as activity that raises your heart rate and makes you breathe harder, such as brisk walking, cycling, or dancing.

The researchers carefully analyzed the data from nearly 90,000 participants who had valid accelerometer data and did not have dementia at the start of the study. They excluded individuals with insufficient accelerometer wear time, those already diagnosed with dementia, and those with certain missing information or conditions like stroke or Parkinson’s disease. For each participant, they calculated the average weekly minutes of moderate to vigorous physical activity based on the accelerometer data. They also assessed frailty using a standard set of criteria, including grip strength, walking speed, weight loss, exhaustion, and self-reported physical activity.

Participants were categorized as robust, prefrail, or frail based on the number of these criteria they met. To determine who developed dementia, the researchers tracked participants’ health records through linked hospital data up to November 2021. They looked for diagnoses of all-cause dementia, using established medical codes to identify cases.

The study’s findings revealed a clear link between even small amounts of physical activity and a reduced risk of dementia. Compared to individuals who engaged in no moderate to vigorous physical activity per week, those who achieved as little as 35 minutes per week had a remarkable 41% lower risk of developing dementia over the study period.

This benefit increased with more activity. Participants engaging in 35 to 69.9 minutes of moderate to vigorous physical activity per week had a 60% lower dementia risk. Those with 70 to 139.9 minutes per week showed a 63% reduction, and those who engaged in 140 minutes or more per week had a 69% lower risk. This pattern suggests a dose-response relationship, meaning that more physical activity is associated with greater protection against dementia.

“Our findings suggest that increasing physical activity, even as little as five minutes per day, can reduce dementia risk in older adults,” said study lead author Amal Wanigatunga, PhD, MPH, assistant professor in the Bloomberg School’s Department of Epidemiology. Wanigatunga is also a core faculty member at the Johns Hopkins Center on Aging and Health and has a joint appointment at the Johns Hopkins University School of Medicine. “This adds to a growing body of evidence that some exercise is better than nothing, especially with regard to an aging-related disorder that affects the brain that currently has no cure.”

Importantly, the researchers found that these benefits of physical activity were evident regardless of an individual’s frailty status. While frailty itself increased the risk of dementia, physical activity still provided a protective effect for frail, prefrail, and robust older adults alike. This indicates that even frail older adults, who may be less inclined to be active, can still gain significant brain health benefits from incorporating even small amounts of movement into their weekly routine.

“This suggests that even frail or nearly frail older adults might be able to reduce their dementia risk through low-dose exercise,” Wanigatunga said

While these findings are promising, it is important to consider the study’s limitations. The UK Biobank participants are primarily from the United Kingdom and may not fully represent the broader population. Like all observational studies, this research cannot definitively prove that physical activity directly causes the reduction in dementia risk; there could be other unmeasured factors that contribute to the observed association.

Also, frailty was measured on average four years before physical activity was measured, so participants’ frailty status might have changed over time. It is also possible that individuals who were already in the very early stages of dementia might have been less active, leading to a reverse causation issue, although the researchers conducted analyses to minimize this possibility. Finally, accelerometers measure the quantity and intensity of movement but do not capture the specific types of activities performed, which could provide additional insights.

Future research could build upon these findings by conducting intervention studies to specifically test whether increasing physical activity, even in small increments, can directly reduce dementia risk in diverse populations, including frail older adults. It would also be valuable to investigate what types of physical activity are most effective for dementia prevention and to explore the biological mechanisms through which physical activity exerts its protective effects on the brain.

Despite these limitations, this study provides hopeful evidence that even a little moderate to vigorous physical activity can be beneficial for brain health and significantly lower the risk of dementia, even for frail older adults. This message is particularly important for promoting public health strategies that encourage physical activity at all levels of ability to help combat the growing burden of dementia.

The study, “Moderate-to-Vigorous Physical Activity at any Dose Reduces All-Cause Dementia Risk Regardless of Frailty Status,” was authored by Amal A. Wanigatunga, Yiwen Dong, Mu Jin, Andrew Leroux, Erjia Cui, Xinkai Zhou, Angela Zhao, Jennifer A. Schrack, Karen Bandeen-Roche, Jeremy D. Walston, Qian-Li Xue, Martin A. Lindquist, and Ciprian M. Crainiceanu.