Small adjustments to your daily routine can go a long way toward protecting your body’s control center and preventing cognitive decline down the road.

In fact, scientists believe that as many as 45 percent of dementia (痴呆) cases could be delayed or prevented with help from some simple, sometimes surprising, changes in behavior.

1. Wear a helmet.

Physically protecting your head is the single most important step you can take to safeguard your brain, experts said.

Recurrent head trauma from traumatic brain injuries and concussions (脑震荡) can lead to chronic traumatic encephalopathy (慢性创伤性脑病), which can worsen cognition overall, and in some cases cause dementia. Wearing a helmet during activities like biking and skiing can significantly reduce the risk of injury, Dr. Feldman said.

Motorcyclists should also always wear helmets, even if state laws don’t require them.

2. Join a book club.

Maintaining an active social life keeps the negative health effects of isolation—such as depression—at bay, said Dr. Jessica Choi, a neurologist at Cedars-Sinai.

Dr. Choi said that her patients who have a strong social support system are typically in better overall health than the ones who don’t. “Not having that can lead to depressive episodes,” which are tied to cognitive decline in older patients, she said.

Book clubs or gardening groups can do the trick, but “even a scheduled monthly dinner with a close friend or family members makes a big difference for patients,” Dr. Choi said.

3. Wear a mask on smoggy or smoky days.

There’s growing research linking air pollution exposure to cognitive decline. Scientists think very fine, inhalable (可吸入的) particles in the air could trigger chemical changes once they reach the brain, said Deborah Cory Slechta, a neuroscientist in the department of environmental medicine at University of Rochester Medical Center.

Not all harmful particles can be avoided—some are so small that they slip through air filters—but wearing an N95 or surgical mask and using indoor air filters on days when air quality is worse (including because of wildfire smoke) can minimize your exposure.

4. Sleep well.

Finding ways to improve your time spent sleeping, and the quality of that sleep, can go a long way toward helping you stay sharp and prevent dementia.

If you work night shifts and sleep during the day, consider blackout (遮光) curtain to help regulate your body’s biological clock. If anxiety and depression are keeping you up, try meditating before bed. If you aren’t sure where your sleep problems lie, keep a sleep diary to help identify potential issues.

“A rested mind is crucial for brain health, as sleep helps consolidate memories and clear out cellular debris from the brain,” Dr. Feldman said.