Your Brain in Your 40s

Investing now — with healthy habits — can pay off later

Ken Budd

Updated July 02, 2024

A man and woman walking across a bridge with their bikes in the mountains

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The 40s are a dynamic time in life, with the hustle and bustle of career, family or both. It’s a dynamic time for your brain too. By middle age, our brains excel at reasoning and using experience to reach strong conclusions, says David S. Knopman, M.D., professor of neurology at the Alzheimer’s Disease Research Center at Mayo Clinic. Emotional intelligence — the ability to understand and manage your own emotions and tune in to others’ feelings — is also strong.

The brain does experience changes during this decade, however. Its overall volume shrinks slightly, as do connections among neurons. And while Alzheimer’s disease — the leading cause of dementia — is rare in people under 50, the biological changes associated with it, such as the buildup of amyloid plaques in the brain, often happen 15 to 20 years before symptoms occur, says Jennifer Rose Molano, M.D., professor in the Department of Neurology and Rehabilitation Medicine at the University of Cincinnati College of Medicine. Health conditions and habits that can eventually lead to vascular dementia, caused by reduced blood flow in the brain, are also common in the 40s. High blood pressure often develops in the early 40s, for instance, and about a quarter of adults are completely sedentary in their free time.

But take heart. What you do now can help protect your brain from the biological changes that can rob you of your memory later, researchers are finding. “In midlife you want to decrease some of the risk factors associated with late-life dementia,” Molano says.

The strategies below may help keep your brain humming. As you’ll see, many factors that influence brain health are interconnected. That means committing to a few basic habits now can help set you up for lasting benefits.

Lower your heart disease risk

Two risk factors for heart disease in midlife — high blood pressure and smoking — increase the risk of developing dementia later in life, according to the National Institute on Aging. Millions of adults with high blood pressure aren't aware they have it, according to the Centers for Disease Control and Prevention. Talk with your doctor and learn about habits that can help lower blood pressure if yours is high. Even slightly elevated blood pressure, which used to be called “prehypertension” and is defined as systolic blood pressure between 121 and 139 mm Hg and diastolic blood pressure between 81 and 89 mm Hg, was linked to cognitive decline in a study of more than 7,000 people in middle age. The study was published in Hypertension in 2020. Smoking does all kinds of damage to your blood vessels, making it harder to get blood to the brain. So quitting is powerful medicine, lowering the risk of dementia until, after nine years, it’s the same as that of people who have never smoked, according to a 2019 report in the Journal of the American Geriatrics Society. Find out about effective ways to quit.

Reduce your odds of type 2 diabetes

Diabetes is a known risk factor for dementia, and the younger people are when they develop the disease, the greater their risk of cognitive decline later in life, according to a long-term study of more than 10,000 adults reported in 2021 in JAMA. The damage diabetes does to blood vessels in the brain can lead to problems with memory and thinking — even within a few years of diagnosis, research suggests. To lower your diabetes risk, maintain a healthy weight, get regular exercise, and follow a whole foods, plant-based diet such as the Mediterranean diet. If you have diabetes, keeping your blood sugar well-controlled may help lower your risk of dementia.

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Make time to move

Regular exercise in midlife may help protect against dementia later in life, according to a 2020 Lancet report. Now's the time to start an exercise regimen if you don’t have one. Ramping up activity levels in middle age, even for those who had been sedentary, was linked to increased longevity in a study of nearly 15,000 adults ages 40 to 79 reported in 2019 in BMJ. National guidelines recommend 150 minutes of aerobic activity every week plus two or three weekly strength-training sessions. But all movement counts, from sweating it out in a fitness class to walking to the corner store to doing housework with vigor. “The Brain-Body Connection,” a 2016 report by AARP's Global Council on Brain Health, recommends doing purposeful exercise and increasing your everyday physical activity to reduce your risk of cognitive decline.

Lose weight — especially belly fat — if you need to

Roughly 44 percent of Americans 40 to 59 are obese, according to the CDC, and that extra weight is not good for the brain. In fact, midlife obesity is the number one modifiable risk factor (meaning you can change it) for dementia, according to a 2022 report in JAMA Neurology. Visceral fat, which accumulates deep in the belly around internal organs and is less visible than the fat that’s right under the skin, may be especially harmful to brain health. “Midlife is when pounds can creep on,” says clinical psychologist Cynthia Green, president of Total Brain Health in Montclair, N.J. “And we know that weight around the midsection is associated with increased risk for dementia.” Middle-aged adults with more visceral fat had more amyloid plaque in their brains, as well as more brain atrophy, in a study of 32 adults ages 40 to 60 published in 2023 in Aging and Disease.

Manage your stress level

Short-term stress is a normal part of life, but unrelenting stress can change the brain, according to the National Institute on Aging. Chronic stress increased the risk of Alzheimer's disease among more than a 1.3 million adults ages 18 to 65, according to a study reported in 2023 in Alzheimer’s Research & Therapy. Being overwhelmed is common in middle age — 38 percent of people in their 40s reported being highly stressed in a 2020 AARP survey — but that doesn’t make it OK. If you're experiencing chronic stress, talk with a therapist, prioritize sleep, get regular exercise and consider starting a practice like tai chi, meditation or yoga. And watch out for work stress, which was linked to reduced cognitive functioning in a 2024 review in Frontiers in Psychology.

Invest in relationships

Social engagement is essential for good health, including brain health — so much so that it’s a focus of the 2023 report from the U.S. surgeon general, “Our Epidemic of Loneliness and Isolation.” The report highlights the harms that accompany loneliness and isolation, including a 50 percent increased risk of dementia in older adults, as well as the physical, cognitive and mental health benefits of staying socially connected. Put time and energy into your friendships and positive family relationships — and consider volunteering as a way to build community. In an AARP survey conducted in 2018 on giving back, people ages 35 to 49 were most likely to report that they planned to volunteer in the next year.

Take shut-eye seriously

Good-quality sleep is important for clearing toxins from the brain, including amyloid, the protein linked with Alzheimer’s disease. But more than 25 percent of adults don’t get enough sleep on the regular, according to the CDC. And people in their 40s sleep the least, according to 2011-2014 data from the “National Health and Nutrition Examination Survey,” including more than 11,200 people reported in 2022 in Scientific Reports. People with sleep apnea may also experience a decline in thinking abilities earlier in life than those who don't have sleep disorders, Molano says. Talk with your doctor or a sleep specialist if you’re having trouble sleeping.

Read more articles about how your brain changes through the decades.