The Truth About Cognitive Decline & What You Can Do About It
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Science has gotten us to a point where we can test for almost everything, including cognitive health. Genetic markers like the APOE4 gene and blood biomarkers like p-tau and amyloid can reveal risk for Alzheimer's and dementia that leads to early intervention.
But these tests leave me wondering: Are we measuring these because they're the most important drivers of cognitive decline, or simply because we can?
On the latest episode of the mindbodygreen podcast, I sat down to discuss this with Tommy Wood, M.D., Ph.D., a neuroscientist, researcher, and author of the new book The Stimulated Mind.
Wood says somewhere between 451 and 70% of dementias may be preventable through modifiable lifestyle factors, including how you move, how you use your brain, and who you spend your time with. This means these habits may have a far greater impact than any biomarker.
So what actually protects your brain against cognitive decline? Here's the protocol Wood suggests.
Why muscle is a brain organ
Muscle mass and strength are known to be strong predictors of cognitive decline. Grip strength is consistently linked to brain aging, and exercises that test lower-body strength (like chair stands) are a studied biomarker of age-related health.
Studies show that resistance training benefits memory and maintains 2white matter in the brains of older adults. White matter sits in the middle of the brain and is responsible for fast connections and complex cognitive functions. Humans have more white matter than any other species, so this increase results in better executive function, working memory, and decision making.
Wood believes IGF-1, a hormone that manages growth in your body, is a key link here. Resistance training increases IGF-1 levels, and throughout the lifespan, IGF-1 is critical for the development and function of white matter. The minimum effective dose is 30 to 45 minutes twice a week, where you exercise the whole body with a basic resistance training program.
The cardio that can actually change your brain
Within two or three hours of sitting, blood flow to the brain drops, motivation drops, and some aspects of cognitive function can decline. To fix this, Wood suggests small bits of movement that he calls exercise snacks. This can look like opting to take the stairs over the elevator between meetings, doing a few squats at your lunch break, or simply standing up and walking around to break up sedentary periods.
From there, aim to increase your step count per day. Walking more steps per day3 is associated with a lower risk of dementia, with the benefit increases starting as low as 2,000 steps. The study also showed that higher intensity movement correlated with a lower risk of dementia.
Wood says the real magic happens with high-intensity exercise. High intensity exercises helps your brain release BDNF, which is a brain-boosting protein. And the modality doesn't matter much for these HIIT workouts. Choose whatever lets you push hard and feel the burn, whether that's cycling, running, or rowing (my personal favorite).
Wood suggests working hard for 30 seconds to a couple of minutes, resting for a similar amount of time, and repeating for 10 to 20 minutes, once or twice a week.
Your brain needs mistakes to grow
Exercise has become so key to brain health because we've engineered movement out of our environment. Now, Wood argues we're engineering thinking out of our daily lives. With GPS, AI, and automation, everything is done for us.
While this may be convenient, Wood says mistakes and errors are the primary drivers of neuroplasticity. When there's a mismatch between what your brain expects to happen and what actually happens, that signal kicks off the machinery to make changes and close the gap. This is how the brain builds new connections.
Wood pointed to the famous London cab driver study4: taxi drivers who memorize 25,000 streets in Central London show structural changes in their brains. You see the same thing in people learning to juggle, speak a new language, or play a musical instrument.
The discomfort of learning something new is exactly the stimulus your brain needs. He recommends everyone pick up one skill their bad at and do it two to three times a week for about an hour.
The social connection piece we're underestimating
In our conversation, Wood reflected on what he had learned from Julian Abel, M.D., a retired palliative care physician who has done groundbreaking work building community connection in towns, and published data showing how it significantly improves health outcomes.
When Wood explained his theory that lack of stimulus drives cognitive decline, Abel pushed back. He said this is all really driven by humans' need for social connection. Most of the time when we're learning complex skills or expressing them, it's in the context of other people. Our social brains are significant drivers of how our brains developed, which is why it's key to continue socializing as you age. Finding community wherever you are, whether it's a religious space, sports team, or residential facility.
And social connection isn't just a mechanism, it's the reason to do all of this in the first place. "Very few people want to live to be a hundred with their cognition intact just so they can sit at home feeling smart. They want to do it so that they can continue to connect with loved ones and spend time with them," Wood says.
The takeaway
The data is clear: cognitive decline is not inevitable. Somewhere between 45 and 70% of dementias may be preventable through the choices you make every day—how you move, how you challenge yourself, and who you spend time with. Take some of Wood's advice, and your brain will thank you for decades to come.