There’s increasing evidence that consistent physical activity can lower the risk of dementia. But not all exervise is the same. New research published in the prestigious medical journal The Lancet suggests that more vigorous exercise may provide more protection.
A better activity measure
The Trøndelag Health Study (HUNT), analyzed data on 29,826 people and used a measure called personal activity intelligence (PAI). While current exercise recommendations are based only on time—150 to 300 minutes of moderate activity or 75 to 150 minutes of vigorous activity per week—PAI digs deeper. It considers your sex, age, resting and maximal heart rate, and heart rate fluctuations over time to estimate exercise intensity and energy expenditure. When your heart rate rises, you earn PAI points. The more it rises, the faster those points accrue.
During an average follow-up of 24 years, the people who earned at least 100 points per week at two time periods during the study had a 25 percent lower risk of developing dementia and a 38 percent lower risk of dementia-related mortality when compared with people who had zero PAI points. Among the people who did develop dementia, those with a high PAI score experienced a later onset (2.8 years) and lived 2.4 years longer.
Because you earn more PAI points with vigorous exercise than with moderate activity, adding more heart-pumping workouts into your week is more protective than spending longer periods on lighter workouts.
Not too late to start
The effects weren’t limited to long-term exercisers. The investigators compared PAI scores from the first phase of the study (1984 to 1986) with scores from a second phase a decade later (1995 to 1997). People who had scores lower than 100 in the first phase were able to reduce their risk of dementia simply by increasing their PAI score to more than 100 by the second phase. In fact, even small increases in the PAI score showed benefits.
How to measure PAI
You can officially track your PAI with a tool such as a fitness tracker or smart watch. If you have a Fitbit, Apple Watch, Garmin, Polar, or Zepp/Amazfit heart rate monitor, you can measure PAI with the app Memento U, which is available in the App Store and on Google Play.
Once you’re geared up to track your progress, you can do any activity you enjoy and that elevates your heart rate. Aim for a combination of moderate and vigorous activity.
If your heart rate is between 60 and 79 percent of your maximum rate, you’re exercising at a moderate level. (You can estimate your maximum heart rate by subtracting your age from 220. Use this formula only if you are healthy, not diabetic, and not taking medications than can affect your heart rate.)
If you get your heart rate to about 80 percent of your maximum, you’re in the vigorous zone. The more time you spend in the vigorous zone, the faster your PAI will rise.
The kind of exercise you need to reach those targets is different for everyone. If you are sedentary, going for short walks throughout the week could be enough to elevate your heart rate, but as you get more fit, your heart gets more efficient, and you’ll need to work harder to elevate your heart rate. You can start with a smaller goal, like 50 PAI points each week, and gradually work up to 100.
You don’t have to be active every day to get to 100. Your total PAI score is calculated over seven days. If you know you can’t exercise on some days, you can “bank” your points by earning more points on others.
While exercise is a powerful way to reduce your risk of dementia, it’s not the only one. Numerous studies show that eating a healthy diet, avoiding smoking, reducing stress, maintaining a healthy weight, and socializing are all important, too.
Beyond Dementia
Attaining a weekly PAI score over 100 does more than reduce dementia risk, according to the Norwegian University of Science and Technology. People who maintain a higher score:
- live an average of 8 years longer
- have a 30 percent lower risk of cardiovascular death
- gain less weight than people who are inactive
- have better exercise capacity, sleep, and lower body fat.
These benefits are seen in men and women of all ages, smokers, and people with diabetes, high blood pressure, or overweight.
