As noted by the study authors, Alzheimer’s disease is in the top ten leading causes of death, and the number of people with dementia is continuing to increase. This study aimed to explore how physical activity before and after dementia diagnosis affected mortality risk, taking into account the level and amount of physical activity.

The study was a nationwide population-based cohort study. Researchers utilized the Korean National Health Insurance System Database to gather information. The study included over 60,000 individuals ages 40 or older who had received a dementia diagnosis between 2010 and 2016. All participants had gotten health check-ups within two years before and after their dementia diagnosis.

The researchers identified people who had dementia based on their use of anti-dementia medications and certain scores that assess dementia. They assessed physical activity using data from the International Physical Activity Questionnaire.

The researchers were then able to break down physical activity levels after dementia diagnosis into categories of vigorous, moderate, and light physical activity and note the amount of exercise per week. They defined regular physical activity as engaging in vigorous physical activity for twenty minutes or more at least three times weekly or engaging in moderate physical activity for thirty minutes or more at least five times weekly.

They then noted how participants’ activity levels changed before and after dementia diagnosis. The average follow-up time was 3.7 years, and during this time, 16,431 participants died. The researchers were able to look at how physical activity related to all-cause mortality.

Overall, the researchers observed “a dose-response association between an increased amount of PA [physical activity] and a decreased risk of all-cause mortality.”

29% decrease in mortality risk

The researchers observed that participants who kept doing regular physical activity before and after dementia diagnosis saw the lowest mortality risk compared to participants who remained inactive, with a 29% reduction in mortality risk.

Compared to non-active participants, participants who increased their physical activity to at least 1,000 metabolic equivalent of tasks (METs)-minutes a week saw a reduced mortality risk. METs have to do with measuring the amount of energy required to perform physical activities.

The researchers also observed a 3% mortality risk reduction for every 100 METs-minutes per week that participants increased physical activity following their dementia diagnosis. There was also a slight reduction in mortality risk for participants with all-cause dementia and Alzheimer’s disease who ceased regular physical activity after diagnosis.

When looking at intensity levels of physical activity, researchers observed that in participants with all-cause dementia and Alzheimer’s disease, maintaining physical activity helped decrease mortality risk, with similar risk reductions in categories of light, moderate, and vigorous physical activity. Among participants with vascular dementia, researchers saw that sustained light or vigorous physical activity was linked to lower mortality risk.

Eric D. Vidoni, PT, PhD, an associate professor of neurology with the KU Medical Center, the University of Kansas, who was not involved in the study, noted the following about the study’s findings to Medical News Today:

“Capturing dementia diagnoses and physical activity on a national level adds compelling evidence to what we already know — that maintaining physical activity supports health, even after a dementia diagnosis. [O]ne of the interesting findings in this study was that light activity held almost as much benefit as moderate and vigorous activity.”

Some limitations exist for this research. First, the study focused on Korean individuals, so there should be caution in generalizing the findings. Additional research with greater diversity could be helpful. Over 60% of participants were women, so it may also be helpful to include more men in future research.

Second, physical activity levels and other lifestyle habits relied on self-reports from participants, which could have had varying levels of accuracy. However, participants could receive help from caregivers in answering questions. It is also possible that people who had less severe dementia and better functionality were more likely to maintain their physical activity levels.

Thirdly, researchers acknowledge that reverse causality is possible. Fourth, using administrative data to note dementia might not perfectly match actual dementia diagnoses.

The researchers also lacked data on the type of physical activity that participants did, and the questionnaire used might not accurately identify shorter periods of physical activity that are still part of overall physical activity. Thus, it’s possible that researchers misclassified or underestimated physical activity levels.

The definition of regular physical activity did not include light physical activity, and researchers considered participants “who did not engage in moderate or vigorous PA as physically inactive.” Thus, additional follow-up may be needed, and this definition could have affected certain analyses.

Finally, the researchers also worked only with data from two check-ups, each within two years of dementia diagnosis: one before and one after. They note that it’s likely that dementia progression and severity for most participants were mild during the study. Thus, it might be helpful to look at additional data regarding people with more advanced dementia.