Protecting yourself from Alzheimer's

Alzheimer's disease is the most common type of dementia: between 60% and 80% of patients with dementia have Alzheimer's. The disease is associated with excessive accumulation of tangles and clumps of protein in and around brain cells. These tangles and clumps make it difficult for brain cells to communicate with one another and may be the reason for the cells' demise.

Scientists don't fully understand what causes some people to get Alzheimer's and others not. However, some factors, like advancing age and family history, are associated with a higher risk. Alzheimer's has no cure, so the primary focus is on slowing the disease's progress once specific biological changes are detected or early symptoms appear. In addition, recent research suggests that it's possible to lower your risk for developing Alzheimer's, no matter your age or family history.

"For people without changes in the brain, it's never too late to reduce one's risk, and even for those with early changes, it's possible to change the odds in your favor and slow cognitive decline," says neurologist Dr. Seth Gale, co-director of the Brain Health Program at Harvard-affiliated Brigham and Women's Hospital.

Imperfect science

It's important to note that most Alzheimer's findings come from population-based studies. Researchers look at the behaviors and medical conditions of people in their 40s, 50s, and beyond and then see who develops Alzheimer's later in life. This allows them to determine if those who get the disease (or those who don't) share specific features or followed particular lifestyle practices.

"It's not perfect, and the findings only show association, rather than direct cause and effect. But they paint an important picture that certain factors are linked with a lower risk," says Dr. Gale. Here are the factors that stand out. Dr. Gale notes that following a combination of the strategies listed here over many years offers the best protection.

Exercise. Multiple studies find that people who engage in regular physical activity have a lower risk for Alzheimer's than those who don't. It's not clear why exercise helps, but the leading theory is that activity increases blood flow to the brain, which likely helps maintain the supply of vital nutrients and energy needed to protect the brain from deterioration over time. "In this way, exercise helps preserve the hippocampus, one of the brain regions responsible for memory," says Dr. Gale.

He adds that studies have not pinpointed whether certain aerobic activities, done for a specific duration, are better than other ones. "Still, a good guideline is to aim for 150 minutes of light- to moderate-intensity exercise per week, like brisk walking, cycling, or tennis," he says. "More is better, and doing something is always better than nothing."

Other research has suggested that doing short bouts of high-intensity exercise may offer the same or greater protection. In a study published online Jan. 11, 2023, by The Journal of Physiology, researchers found that six minutes of high-intensity exercise (in this case, cycling) increased the production of a specialized protein called brain-derived neurotrophic factor (BDNF). BDNF helps with learning and memory and might protect the brain from age-related decline and dementia. While lighter-intensity cycling also done for six minutes increased BDNF, the brief, vigorous exercise was more effective.

Diet. People who follow a plant-based diet like the Mediterranean or MIND diet appear less likely to develop Alzheimer's. While the two eating plans are similar, the Mediterranean diet recommends vegetables, fruit, and three or more servings of fish per week, while the MIND diet prioritizes green leafy vegetables like spinach, kale, and collard greens, along with other vegetables. The MIND diet also endorses berries over other fruit and recommends one or more servings of fish per week. A study published online March 8, 2023, by Neurology found that people who followed either diet had fewer of the Alzheimer's-associated protein clumps and tangles in their brains compared with people who did not consume such diets.

Blood pressure. Over time, high blood pressure can damage blood vessels throughout the body, including the brain. Scientists have found that lowering high blood pressure can protect against dementia. There is debate about the optimal number to reduce the risk of cognitive impairment and Alzheimer's.

For example, in 2019, the SPRINT MIND study suggested that a target of less than 120 millimeters of mercury (mm Hg) for systolic blood pressure (the top number) is better for brain health than 120 to 140 mm Hg. However, a later study, published in January 2022 in Hypertension, found that Alzheimer's risk was most significant among people with systolic blood pressure above 160 mm Hg, with an unclear reduction of risk below that number. "Work with your doctor to find an optimal number that is good for both your heart and brain," says Dr. Gale.

Hearing and vision. A study published online April 13, 2023, by The Lancet Public Health found that among people with hearing loss, those who did not use hearing aids had a 42% higher risk for dementia compared with those who used hearing aids. The possible connection? Wearing a hearing aid might delay cognitive decline by preventing cognitive overload — that is, by keeping the brain from working too hard to process sounds and information.

Studies also have found that older adults with impaired vision — like declining eyesight, cataracts, glaucoma, and age-related macular degeneration — are at increased risk of developing cognitive problems.

As with hearing, correcting vision problems may lower a person's risk. A study published in 2022 in JAMA Internal Medicine found that those who had surgery to remove their cataracts were 30% less likely to be diagnosed with dementia in later years than those who didn't have the surgery.

The connection between vision problems and dementia might be indirect, says Dr. Gale: poor vision may promote inactivity, which is known to increase dementia risk. "It is also possible that poor vision leads directly to the breakdown of brain processes that rely on vision. This impairs overall brain networks and could increase the risk of losing more brain cells," he says.

Stimulation. While the science linking brain-engaging activities with a lower risk for Alzheimer's is ongoing, experts meanwhile recommend stimulating the mind as much as possible. This can include joining social clubs, learning new skills, reading, doing puzzles, and playing games.

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