Your Brain is like a Reservoir. Replenish it with Healthy Activity.

I’ve often heard patients express the same wish for old age: They want to live independently in good health, postponing serious illness and disability until the very end. Research suggests our generation has a better chance than our ancestors of experiencing old age with less illness. Socioeconomic and medical advances have allowed many people to prevent or postpone common conditions of aging, especially heart disease and maybe even Alzheimer’s disease.

Protecting our brain health involves building so-called “cognitive reserve”—a process that likely starts before birth as a fetus’s brain takes shape. It continues throughout life as brain structure changes in response to our experiences and environment. Some experts believe brain development can persist up until the time we die.

You can think of your brain like a reservoir, gathering rain for later use over time. Many things happen throughout life to drain and refill your reservoir. Your brain can build and maintain a reserve of cells and connective structures allowing it to continually adapt and function, staying resilient in the face of stress and strain. Your level of reserve is likely to fall as the size of the brain naturally shrinks with age, but certain activities may act like spring storms, replenishing reserves for better function—even in old age.

Factors affecting your brain reserve can include your choice of work and leisure activities, social relationships, level of physical exercise, and getting enough sleep. The more intellectually challenging your activities, the lower your risk of developing dementia and the slower your rate of cognitive decline. You want to avoid too much emotional stress, too much sitting, and too much passive, repetitious activity.

When it comes to hobbies, people who pursue games like bridge or other mind-challenging pastimes appear to have better brain health than those who choose passive activities like watching television. Some research suggests that dance is an ideal hobby because of its unique combination of exercise, socializing, and mental work needed to get the steps just right.

Your social life is also important for promoting healthy brain aging, avoiding dementia, and preventing other chronic illnesses. Having a supportive network of family and friends correlates with dodging early death in general. The reasons are many and complex. But basically, we need other people around to keep us talking, thinking, working, moving, caring for ourselves, and generally engaged in our lives—all necessities for good brain health.

Setting intentional goals for friendship and family relationships becomes increasingly important in old age when we naturally lose friends and family due to death or moving away. It’s the quality and not just the quantity of these relationships that seem most important. It’s good to have friends with whom you can share interesting conversations and meaningful activities—people who inspire you to get going every day, pursuing activities that get your blood pumping and stimulate your brain.

Everybody eventually has some loss of memory and cognitive function with age. Like any body part, your brain undergoes wear and tear. And there’s certainly nothing you can do about past experiences that may have already affected your brain reserve (such as playing youth football or taking harmful drugs over a long period of time).

But you can take steps today to maintain or build healthy habits like exercise and an active social life. Doing so, you can minimize the drain of your brain reserve and refill your reservoir for a net gain of healthy years.

Dr. Eric B. Larson is vice president for research and health care innovation at Kaiser Permanente Washington and author of the book Enlightened Aging: Building Resilience for a Long, Active Life.