People are afraid of dementia and Alzheimer’s disease since we don’t understand the diseases very well. But there’s some good news — a recent paper stated that walking could reduce the risk of dementia — could it be that simple?
As I get older, I worry about declining executive function along with a risk of dementia or Alzheimer’s disease. So far, I’m doing well. I attempt to walk between 10 to 20 thousand steps every day for the past decade, so this type of science is personally interesting.
Like I always do, I will present the key findings of the peer-reviewed paper, and then tell you what I think about the article. So let’s get to it.
Walking and dementia paper
In a paper published on 6 September 2022 in JAMA Neurology, Borja del Pozo Cruz, Ph.D., of the University of Southern Denmark in Odense, and colleagues examined longitudinal data from records in the UK Biobank. This database provides investigators with the respective contributions of genetic predisposition and environmental exposure (including nutrition, lifestyle, medications, and others) to the development of disease.
The study assessed daily step count from wrist-worn accelerometers for 78,430 people 40 to 79 years old in the UK Biobank cohort from February 2013 to December 2015. Researchers evaluated the total number of daily steps, whether steps were incidental (less than 40 steps per minute) or purposeful (40 or more steps per minute). They examined the peak 30-minute cadence (average steps/minute for the 30-highest minutes of the day, which were not necessarily consecutive).
The major findings of the research were:
- A daily total of 3,800 to 9,800 steps was tied to lower dementia risk.
- The optimal “dose” of daily steps — the value with the highest dementia risk reduction — was 9,826 steps, hazard ratio (HR) = 0.49, or 51% reduction in risk of dementia.
- The minimal daily step dose — the point at which dementia risk was half of the maximum reduction — was 3,826 steps per day, HR = 0.75, or a 25% reduction in risk.
- Interestingly, the intensity of walking mattered to the reduction of the risk of dementia. The optimal walking cadence dose for the highest 30 minutes of the day was 112 steps per minute, HR = 0.38, or a 62% reduction in risk.
The researchers concluded:
In this cohort study, a higher number of steps was associated with lower risk of all-cause dementia. The findings suggest that a dose of just under 10 000 steps per day may be optimally associated with a lower risk of dementia. Steps performed at higher intensity resulted in stronger associations.
These are very interesting results and are very significant. If these studies showed only a 5 or 10% reduction in risk, I’d shrug my shoulders and move on to some other research.
The strong points of this study are the large population size, over 78,000 subjects, the use of wrist-worn accelerometers (like a Fitbit or Apple Watch) for accuracy, and the strong statistical differences.
However, and I’m going to sound like a broken record, confounders could affect the data. For example, people who walk more may be less obese or eat a better diet. The researchers seemed to take into account some confounders. Their models “were adjusted for age, sex, race, education, socioeconomic status, smoking, alcohol use, fruit and vegetable consumption, family history of cardiovascular disease and cancer, medication use, accelerometer-measured sleep, and valid accelerometer wear days.” They also set up a separate model that was “adjusted for cholesterol, hemoglobin A1c, body mass index, and mean arterial pressure.”
As I discussed in another article that used the UK Biobank database, it does rely upon self-reporting of some data (like diet), so that might cause some weakness in the data. However, the use of accelerometers does decrease the chance that individuals are exaggerating their steps (though there are ways to cheat).
In the end, given that the researchers used a solid model, tried to account for confounders, and performed a good statistical analysis, the significant reduction in dementia risk with increased walking steps (which shows a dose-response effect) is pretty convincing.
Also, this study just looked at walking. We don’t know if these results would be repeated for other aerobic exercises such as running, swimming, bicycling, and other exercises. That sounds like a good research goal for a new epidemiologist out there.
We do not know why this happens. Maybe walking leads to better fitness which leads to something in the brain that reduces the risk of dementia, but we’re a long way from establishing causality. If nothing else, this inspires me to continue my walking, although it appears I have to pick up my pace very slightly.
Skeptical Raptor rating
I’m going to give this study 4 out of 5 stars. I think the size of the effect is very large, the study methods were good, and the statistical analyses seemed more than adequate. They accounted for some confounders.
To get 5 stars I’d like to see other studies on other groups of people (this was only the UK) and a better description of biological plausibility.
But for now, I’m going to keep walking.
- Del Pozo Cruz B, Ahmadi M, Naismith SL, Stamatakis E. Association of Daily Step Count and Intensity With Incident Dementia in 78 430 Adults Living in the UK. JAMA Neurol. 2022 Sep 6. doi: 10.1001/jamaneurol.2022.2672. Epub ahead of print. Erratum in: JAMA Neurol. 2022 Sep 9;: PMID: 36066874.