Alzheimer’s disease (AD) is a condition that many of us worry about as we, or our loved ones, get older. It gradually affects memory, thinking, and the ability to carry out daily tasks. While there’s no cure yet, and there are many risk factors for developing this condition that are out of our control (like our genetics), research suggests that nearly half of all cases worldwide could be linked to modifiable risk factors, meaning they are things we might have some control over. One of the most significant of these factors is physical inactivity.

Scientists have long suspected a link between exercise and brain health, but much of the evidence came from animal studies or from people self-reporting their activity levels, which can be unreliable. A recent, long-term study from the Harvard Aging Brain Study aimed to get a clearer picture. Researchers wanted to know if objectively measured physical activity, like the number of steps you take each day, could slow down the brain changes associated with Alzheimer’s disease, even before symptoms appear. The results of this study were published in Nature Medicine.

How Was the Study Conducted?

To conduct this study, researchers followed a group of 296 older adults who were cognitively healthy at the start of the study. This was a longitudinal study, meaning they tracked these individuals for up to 14 years to see how things changed over time.

Participants wore a pedometer on their waistband for seven consecutive days. This device counted their daily steps, providing a reliable, objective measure of how much they moved, unlike simply asking them to remember their activity levels. Participants also underwent annual check-ups to assess their cognitive and functional abilities. Most importantly, the researchers used advanced brain imaging techniques. A subset of participants had regular positron emission tomography (PET) scans to look for the two hallmark proteins of Alzheimer’s disease:

• Beta-amyloid (Aβ): Sticky plaques that build up between nerve cells.


• Get: Tangles that form inside nerve cells.

By tracking these proteins, along with cognitive scores and daily step counts over many years, the researchers aimed to determine if both factors were connected.

What Did the Study Find?

The study found that physical activity didn’t seem to affect the buildup of amyloid plaques. However, it had an impact on the spread of tau tangles and the rate of cognitive decline, especially in people who already had amyloid in their brains.

Here are the key takeaways:

• Slower Tau Buildup: In individuals with high levels of amyloid, being more physically active was associated with a slower accumulation of tau tangles in the brain. This is a crucial finding because tau is more closely linked to memory loss and other symptoms of Alzheimer’s.


• Slower Cognitive Decline: More active participants showed a slower decline in their cognitive scores. This protective effect was most noticeable in those at high risk for Alzheimer’s. The buildup of tau accounted for a large part of this benefit, mediating 84% of the link between activity and slower cognitive decline.


• Slower Functional Decline: Similarly, higher physical activity was linked to slower functional decline, meaning people maintained their ability to manage daily life for longer. Compared to inactive individuals, those with at least low activity levels saw a 34% to 51% slower decline in function over a nine-year period.


• A “Dose-Response” Effect: The study also looked at how much activity was needed. The biggest benefits were seen when people went from being inactive (less than 3,000 steps per day) to having low activity (3,001-5,000 steps). The positive effects continued to increase up to a moderate activity level (5,001-7,500 steps) before plateauing. This suggests you don’t need to run a marathon to see a difference.

For people with elevated amyloid, moving from an inactive lifestyle to a low-activity one was estimated to delay significant cognitive worsening by about three years (from 6.5 years to 9.6 years). Reaching a moderate activity level could potentially add even more time, delaying decline to over 13 years.

What Were the Limitations?

While this study offers valuable insights, it’s important to consider its limitations. First, the research was observational, which means we can’t be certain that physical activity directly causes slower Alzheimer’s progression. Instead, there could be other factors involved. The study measured physical activity only at the beginning of the study, so we don’t know how changes in activity over time might influence the results. Additionally, participants were mostly highly educated, non-Hispanic white individuals, which may limit how well the findings apply to other groups with different backgrounds or lifestyles.

How Does This Apply to Real Life?

The findings from this study are not just for scientists; they have direct, practical implications for all of us. The most encouraging news is that you don’t have to become a super-athlete to protect your brain.

The popular goal of 10,000 steps per day can feel daunting, especially for older adults or those who have been sedentary for a long time. This study suggests that a more approachable goal of around 5,000 to 7,500 steps per day can provide substantial benefits. Even a modest increase in daily steps for the most inactive individuals can make a huge difference.

For someone with a high risk of Alzheimer’s, this means that adding a daily walk to your routine could potentially delay the onset of symptoms by several years.

Our Expert Take

This study published in Nature Medicine provides some of the strongest evidence to date that physical activity can directly impact the course of Alzheimer’s disease in the brain. By using objective step counters and long-term tracking of amyloid and tau, researchers demonstrated that being more active helps slow the spread of tau tangles, which in turn preserves cognitive and functional abilities.

The message is clear and empowering: moving more matters. While it may not be a magic bullet, incorporating more physical activity into your daily life is a practical and effective strategy to build brain resilience. For those at risk of Alzheimer’s, taking those extra steps each day could be one of the most important things you do to protect your mind and your future.