More Americans are poised to live past 100. It could be a lonely future for many of them.

• Americans are living longer; globally, the number of centenarians is projected to increase eightfold by 2050.
• Because of this, we'll likely face isolation, which can have a dramatic effect on our health.

The house I grew up in once pulsed with the happy chaos of life's daily dysfunction. Today, with my mother as its sole occupant, it's mostly quiet, save for the low-volume chatter of a TV that's almost always on somewhere.

There are three screens: one in the kitchen, another on the back porch, and a third in Mom's bedroom. My younger brother and I each drop in once or twice a week, but she's 92 now, so those TVs are her most faithful companions. Dad's been dead for more than two decades, and tragically, we lost our middle brother two years ago.

For Mom, who has buried both parents, a husband, a son, three siblings, several nieces and nephews, and too many friends and neighbors to count, longevity comes with a curse. It is the dull ache of loneliness — reflected in every framed family portrait; every personalized calendar; every faded, oxidized Polaroid snapshot taped to the side of the fridge. They're gone, and she's still here.

An increase in longevity comes with serious health risks

America is rapidly aging, holding out the promise of 100-year lives to many more of us than ever before. Globally, the ranks of centenarians are projected to increase eightfold by 2050. But there's a downside: the risk — even the likelihood — that we'll outlast those we care about the most and live out our extra days in social, if not physical, isolation.

Underscoring how much we need one another — and how that interdependence affects our physical and emotional well-being — US Surgeon General Vivek Murthy recently proclaimed loneliness a nationwide public-health epidemic. The World Health Organization has said one in three older adults feels lonely. And all that solitude is taking a toll on our minds and bodies that experts liken to the deadly effects of obesity or alcoholism.

The National Institute on Aging says the health risks of prolonged isolation are equivalent to smoking 15 cigarettes a day and may shorten a person's life span by as much as 15 years. Like stress, it can trigger inflammation throughout the body and elevated levels of cortisol and other hormones that can increase blood pressure.

Eventually, as significantly more of us age into triple digits, we'll have more company. But a society where 100 is the norm is decades away — and until then, many centenarians will have to reckon with some measure of solitude.

Why loneliness isn't the same as just being alone

"I've been forgotten by our good Lord," France's Jeanne Calment, the oldest person who ever lived whose age can be authenticated by records, ruefully said as she approached 122, having painfully outlasted those closest to her. A devout Catholic, the woman some geriatricians nicknamed "the Michael Jordan of aging" often spent her mornings in prayer, asking God a simple, plaintive question — one we'll never know whether he answered:

Pourquoi? Why?

Most Americans 65 and older say they'd happily live to 100 and beyond, but only under certain conditions. More than half worry that old age is too risky to be worth the trouble.

Loneliness, by the way, isn't the same thing as being alone. Introverts like me can attest to the restorative power of withdrawing from others to recharge. When I need a break from the rest of you, I go for a long run, a solo day sail on Rhode Island's Narragansett Bay, or steal away for some fly fishing where it's just me and the trout — all solitary pursuits.

But those are personal choices. Loneliness is the inner anguish that springs from craving companionship and camaraderie only to be deprived of them. Researchers have found evidence of a greater likelihood of depression, suicide, dementia, Alzheimer's disease, a compromised immune system, and a heightened incidence of heart attack and stroke among seniors who complain of feeling lonely.

Of course, centenarians, like the rest of us, aren't a monolith. Some manage to navigate and overcome loneliness on their way to achieving exceptional ages. "Centenarians are vulnerable and resilient at the same time," a team of researchers at Fordham University concludes.

My grandmother was born in 1899 and died in 2003, just shy of her 104th birthday, after a life that touched parts of three centuries. Little wonder that her daughter, my mom, is ambivalent at best as she makes her own uneasy way along the road to 100.

"I just enjoy my life," she tells me with a shrug. "When your time is up, it's up. That's it."

Excerpted from "The Big 100: The New World of Super-Aging" (Diversion Books, October 3, 2023). Reprinted with permission from Diversion Books.