This is what scientists call “squaring the curve.” Put differently, it means that our “health span” — the years in which we are healthy and active — can last almost our entire lives. And that’s something that, to a significant extent, we can control.

Up to age 80 or so, longer life is mostly due not to genetics, but to environmental factors, including healthy behaviors such as physical activity, says Daniel Lieberman, chair of the department of human evolutionary biology at Harvard University.

Before modern medicine, Lieberman adds, “Life span was determined by health span. Our hunter-gatherer ancestors had to be active until they died. In turn, staying active turns on the processes that keep the body healthy.”

Steven Austad, a bio-gerontologist at the University of Alabama at Birmingham and senior scientific director of the American Federation for Aging Research, says: “As a species, we did a lot of physical activity for 300,000 years, until very recently.”

For us modern folk, the formula for maximizing our health span can be as straightforward as getting off the couch and walking or doing some other physical activity — you don’t even have to call it exercise — almost every day. It means eating right — more veggies, fewer doughnuts. Connecting with other people to keep loneliness at bay. And avoiding hazards like scatter rugs and cluttered hallways that lead to broken hips, and, all too often, shortened lives.

We now live in a world with growing numbers of old people, including people older than 100. So, what is accounting for longer lives?

Essentially, we have had a safer environment since the 1900s, with basic public health standards when it comes to such things as water, working conditions, refrigeration, and vaccinations, says Tom Perls, professor of medicine at Boston University and director of the New England Centenarian Study, the world’s largest ongoing study of people age 100 and older. Those factors have allowed more people to live past childhood illnesses and injuries into adulthood.

But making it to 100? Or 105? At that point, Perls says, it’s not good behavior so much as pure luck — in the form of genes. The centenarians he has studied all fit 27 genetic patterns. These genes slow aging and decrease the risk of age-related illnesses such as heart disease, stroke, cancer, diabetes, and dementia.

There may actually be an evolutionary advantage to having older folks around. Think about the resources that grandparents often provide — food, baby-sitting, college tuition — that can help family genes get passed down by supporting younger generations to reach reproductive age.

Then there’s the invaluable knowledge that older people bring to our communities. I saw this firsthand in 1993 when the Globe sent me to a Navajo reservation to report on a deadly outbreak of hantavirus — a group of viruses associated with rodents — rocking the Four Corners region of the Southwest. It was the tribal elders, speaking to researchers from the Centers for Disease Control and Prevention, who provided key information.

The elders remembered that earlier in the 20th century, they had observed increased rainfall, which led to more piñon nuts, which led to more deer mice, which led to more mouse poop, which aerosolized. Then, when inhaled, this toxic dust infected tribal members’ lungs.

The bottom line is that an increased health span can benefit not only you, but your loved ones as well. Here are five ways that you can live a healthier, longer life.

1. Exercise your body . . . for your brain

Scientists have long known that exercise is crucial for protecting against heart disease, the leading killer of Americans.

A study published in 2008 by the European Journal of Cardiovascular Prevention and Rehabilitation found that physical activity reduced the risk of dying from heart disease by 35 percent, and the risk of dying of any cause by 33 percent.

Indeed, physical activity is “the single most important thing for healthy aging,” says Austad. “It doesn’t have to be sweat-dripping-in-the-eyes exercise. Any kind of physical activity helps.”

But what many do not know is that exercise is also the best thing you can do for your brain. It does two important things: It boosts cognition and elevates mood.

This is thanks to something known as brain-derived neurotrophic factor, a chemical dubbed “Miracle-Gro for the brain” by Dr. John Ratey, an associate professor of psychiatry at Harvard Medical School. “BDNF is the magic factor, both in mood and cognition,” Ratey says. “Nothing protects the brain more than exercise. We make the most BDNF with exercise.”

According to Ratey, while games such as Wordle activate a small part of the brain, brain-derived neurotrophic factor activates more areas, including the hippocampus, the brain’s chief memory center, increasing the nerve cells there. A shrinking hippocampus is involved in both Alzheimer’s disease and major depressive disorder.

In July, researchers reported that when regular participants in cycling classes increased their workouts from one or two sessions a week to four, they saw significant increases in both cognition and mood.

Lack of exercise has been found to be a leading modifiable risk factor for preventing Alzheimer’s disease. According to a 2013 study by the Ontario Brain Institute, if everyone who is currently inactive were to change their lifestyle and become active, 1 in 7 cases of Alzheimer’s could be prevented.

And all it would take is moderate-intensity exercise, such as brisk walking, for 150 minutes a week — or 30 minutes a day for five days, according to the study. (If you’re still looking to bolster your brain, here’s an extra sweetener: chocolate. The biomolecules in chocolate have been found to boost cognition.)

Research also shows that physical activity can lift your mood. A meta-analysis conducted by an international team of researchers and published in 2016 showed that exercise has a significant effect on depression. Other researchers have found that a single session of aerobic exercise can improve mood.

Moreover, BDNF appears to be the link between antidepressant drugs and the brain changes that result in reduced depressive symptoms, a team of researchers from Sweden and Texas found.

BDNF, they noted, has consistently been highlighted as a “key player in antidepressant action.” Even just one infusion of BDNF into the brain is “sufficient to induce a relatively rapid and sustained antidepressant-like effect,” they said.

The bottom line, dare we say, is a no-brainer. As Ratey puts it, “Get outside and move. The best exercise is something that is fun and will have you coming back to do it.”

2. Unlock the mysteries of the microbiome

Usually, when we think of the bugs — mostly bacteria — that live in our guts, noses, mouths, and other nooks and crannies, it is only when they make us sick.

But in recent years, researchers have been studying the “good” bacteria, fungi, viruses, and other teeny organisms that live inside us and actually keep us healthy. These microbes have been evolving alongside us for eons. (A person’s microbiome is the collection of all the microbes in the body.)

A healthy gut microbiome has been shown to play a key role in providing energy, producing vitamins and nutrients, and creating a strong immune system. An unhealthy microbiome — one with a less diverse microbial population — has been correlated with numerous digestive and other problems.

Diet has a huge role to play in maintaining a healthy microbiome.

“The best diet is one that is rich in prebiotics,” says Dr. Dariush Mozaffarian, dean for policy at the Friedman School of Nutrition Science and Policy at Tufts University. Prebiotics, a food source for good bacteria in your body, are different from probiotics, which are bacteria, and often sold as supplements. Prebiotics are found in blueberries, cocoa, tea, coffee, and other foods rich in fiber, such as nuts, seeds, fruits, vegetables, beans, and minimally-processed whole grains, he adds.

Also important are probiotics, which can be found in fermented foods like yogurt, kefir, sauerkraut, and kimchi, as well as cheeses that have been aged but not heated afterward, such as aged feta, Swiss, provolone, Gouda, cheddar, Gruyere and cottage cheese. A study conducted in India found that babies given a microbiome boost from probiotics were 40 percent less likely to contract infantile sepsis.

As for commercially available probiotics, Mozaffarian is cautious. “We know [probiotics] are critical, but we don’t know the exact strains of bacteria or the doses right now. There’s more noise than science in the marketing.”

While prebiotics and probiotics can be beneficial for a healthy microbiome, unfortunately for steak lovers, red meat may be a serious no-no, as well as for a healthy heart, according to Tufts researchers.

Published earlier this year and co-led by postdoctoral fellow Meng Wang at the Friedman School, the study looked at nearly 4,000 men and women over 65. Higher meat consumption was linked to a higher risk of cardiovascular disease, as expected, but equally important, 10 percent of this risk was explained by increased blood levels of three chemicals made by gut bacteria.

“To reduce blood levels of these chemicals,” says Wang, “limiting red and processed meat intake is a good idea.”

The role of diet in maintaining a healthy microbiome shouldn’t be underestimated. In a 2015 study, researchers asked a group of African Americans, who are disproportionately impacted by colon cancer, to switch to the low fat, high fiber diet typical of rural South Africans, who are far less impacted by the disease. The South African participants, in turn, switched to a “western-style” diet higher in fat and lower in fiber.

The microbiomes of both groups changed markedly — in a healthy direction for those switching to a high-fiber diet and in an unhealthy direction for those decreasing fiber.

3. Win the inflammation war

Inflammation is a sneaky thing.

When we cut a finger and see the hot, red swelling around the cut, or take a flashlight and look at the swollen tonsils of a bad cold, the inflammation is obvious, proof of the body’s healthy immune response to injury and infection.

After that cut heals or the sore throat goes away, the inflammation subsides and we go on with life. Indeed, we couldn’t survive without this powerful immune defense.

But there’s another kind of inflammatory response — an insidious one that actually threatens our survival. This is what happens when that good inflammatory response doesn’t shut down properly when the danger is over, but keeps on going for days, months, and years at a low level.

This chronic inflammation is what underlies many of the conditions that plague us, especially as we age: insulin resistance (a precursor of diabetes), atherosclerosis, Alzheimer’s, stroke, and neurodegeneration, to name just a few.

The culprit behind this bad inflammation is what is known as visceral fat. This is not fat that is visible under our skin, but the kind that is hidden deep in our abdomens and is actually an active endocrine organ.

Visceral fat pumps out inflammatory chemicals called adipokines, part of the family of chemicals called cytokines. Some cytokines shut inflammation down, others trigger it. It’s the constant output of the latter that is so harmful.

“It can be thought of as the immune system running amok,” says Dr. I-Min Lee, an epidemiologist and professor of medicine at Harvard Medical School. “High levels of chronic inflammation contribute to development of heart disease, cancer, even dementia.”

With atherosclerosis — often described as a “hardening of the arteries” — for instance, the problem begins with the buildup of fat and cholesterol in artery walls. The body sees these deposits as foreign and sends in white blood cells — inflammation — to attack the problem, causing plaques. Over time, these plaques can narrow the arteries and trigger blood clots. “Inflammation inside artery walls causes plaque to thicken and harden,” Lee says.

Exercise is a powerful weapon in this regard. “Even without weight loss, exercise leads to a lower level of chronic inflammation,” Lee says.

Austad, of the American Federation for Aging Research, says exercise has additional benefits when it comes to inflammation.

“Exercise induces anti-inflammatory chemicals and helps prevent senescent cells, which pump out harmful pro-inflammatory chemicals,” he says. Dubbed “zombie” cells because they are difficult to kill, senescent cells are alive but cannot reproduce.

A good diet also helps reduce chronic inflammation, especially one low in trans fats from meat and deep-fried or processed foods.

4. Reduce fall dangers at home

Little kids do it for fun. Skiers do it by accident, but usually survive. But when older people fall, the results can be disastrous.

Compared with the many other health hazards that older people face, falls may not make it onto the public radar. But they can be not only life-altering, but, all too often, fatal. Falls are the leading cause of injury and injury deaths in older Americans, according to the CDC.

If you break your hip, there’s a more than 20 percent chance that you will die in the first year afterward, according to a 2010 study, though some estimates put the risk much higher.

It’s not the damage to the hip itself that is so deadly, but that a person who falls may already be “frail and suffering from other medical conditions — then become immobilized for a long period afterward,” says Dr. David Slovik, an associate professor of medicine at Harvard Medical School. “That lengthy period of bed rest can lead to pneumonia, blood clots, and other medical problems.”

“That’s why exercise and fall prevention are key,” adds Slovik, an endocrinologist and osteoporosis specialist at Massachusetts General Hospital.

Weight-bearing exercise used to be thought of as a powerful way to strengthen bones, even in later life. It turns out, though, that even high-intensity exercise and working out with weights don’t strengthen bones significantly. But exercises such as walking and stair-climbing can strengthen muscles and improve balance. “And good strength and balance mean you’re less likely to fall,” Slovik says.

Indeed, a 2018 Tufts University study conducted at the Somerville Council on Aging showed exactly that. When exercise classes were introduced at the center, there was a 60 percent reduction in falls.

Published in 2022, a study of 61,200 post-menopausal women across 11 US states showed that the risk of hip fracture was lowered by 6 percent for each increase of one hour per week of walking. Participants who walked at least four hours a week, but did no other exercise, had a 41-percent lower risk of hip fracture.

There are also a number of practical things you can do to prevent falls. In addition to strength training for strong muscles, try to practice standing on one foot while holding on to a chair, or consider learning tai chi. If you start to fall, try not to fall sideways but, instead, onto your rear end.

It’s also important to fall-proof your house. Remove hazards such as scatter rugs, long extension cords, and junk that’s lying around. Install good lighting, especially in the bedroom, bathroom, and the spaces between them. Put handrails in the bathroom and use nonskid rugs near the toilet, bath, or shower.

Other tips: Mop up spills. Keep frequently-used items where you can reach them without climbing on foot stools or chairs. Always use the handrails on stairs.

And, of course, try not to trip over the dog.

5. Make time for friends

More than a century ago, a small group of Italians left their little village, Roseto Val Fortore, in the foothills of the Apennines, in search of a better life in the slate quarries of eastern Pennsylvania.

When they got there, they named their new village Roseto and quickly reestablished the close-knit ties they’d had in Italy. They lived in three-generation households, their houses so close together that to chat they just headed out to the front porch.

In the 1960s, Roseto became a magnet for researchers. The little town shared a water supply, as well as doctors and hospitals, with nearby towns, but had significantly fewer heart attacks compared with neighboring communities. Not that the Italian villagers were models for healthy habits — they smoked cigars, drank wine, and ate meatballs and sausages fried in lard, not to mention cheese. Yet, they were healthier.

Genetics didn’t explain the discrepancy, now known as the “Roseto effect.” So what made the difference? As researchers would document over and over for decades — most recently in a 2020 report commissioned by the AARP — the answer boils down to human connections.

“We’ve known for decades that social isolation and loneliness are risk factors for poor health and earlier mortality,” says Dr. Nancy J. Donovan, a psychiatrist at Brigham and Women’s Hospital and coauthor of a 2020 analysis of those research results. “Up until recently, these major risk factors have not been addressed in health care settings.”

Social isolation and loneliness are major concerns for people over 50, the report noted, because that age group is more likely than younger people to live alone, to have lost close friends or family members, and to be living with chronic illnesses and sensory impairments.

Being socially isolated is linked to a significantly increased risk of premature mortality from all causes, as well as, specifically, an increased risk of dementia, coronary heart disease, and stroke.

To be sure, not all older people are socially isolated, just as not all lonely people are older. The people at highest risk of loneliness, research shows, are people in their late 70s and older, and those in their late teens and early adulthood, despite, in the latter case, active lives and online connections.

The key is “to stay active and connect with others,” says psychologist Elizabeth Necka, a program director at the National Institute on Aging. “People who engage in meaningful, productive activities with others feel a sense of purpose and tend to live longer.”

It also helps to focus on interests and activities that you truly enjoy and use those to connect with other people, adds Donovan.

“People’s social connections got frayed during the pandemic,” she says. “But I think we can achieve a new normal.”

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Judy Foreman is the former Globe Health Sense columnist and author of the 2020 book Exercise is Medicine, from Oxford University Press. Send comments to magazine@globe.com.