Brain Rules for Aging Well. John Medina
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forty-five, levels a bit, and continues its decline after fifty-five, completing the U shape of loneliness.
There are many caveats and nuances to these data, so the U curve’s a bit wobbly. Seventy-five-year-olds experience some of the least feelings of loneliness in life, followed by the most a month or two after their eightieth birthday. Seniors who don’t make much money experience severe loneliness more sharply than seniors who do: a monstrous threefold increase. Married people experience less loneliness than those living alone. This is true for all age groups, but the quality of intimacy plays a larger role for the marital well-being of seniors than of younger people. Physical health plays a powerful role in how much isolation the elderly suffer, too.
Where social isolation leads
The more socially isolated you become, the less happy you are. Researchers believe the reasons for this are deeply rooted in evolution: humans were too weak, biologically speaking, to survive without each other for long. Our brains created a system of negative responses to social isolation, compelling us to seek each other out. Cooperation and the mentalizing tools we developed for it put us squarely into the Darwinian carpool lane. We then survived long enough to pass along our genes.
We don’t do very well when we get lonely. For one, our social behaviors begin eroding. Loneliness is associated with poorer grooming habits, for example, and an increasing inability to navigate intimate life functions such as bathing, using the toilet, eating, dressing independently, and getting out of bed. Some of this may be related to the oncoming squalls of depression, gusts to which lonely seniors are particularly vulnerable.
Lonely seniors have poorer immune function. They can’t fight off viral infections or cancers as easily. They have higher levels of stress hormones, which bring on all kinds of negative effects. Chief among these are higher blood pressure, which increases the risk for heart disease and stroke. Loneliness hurts overall cognition too, from memory to perceptual speed. It’s even a risk factor for dementia.
Chronic loneliness can throw you into a nasty loop. As you probably know, the process of aging involves physical pain: certain tissues begin to break down for which there will be no cure; aches intensify in specific body parts naturally vulnerable to aging (arthritis is but one example). Such discomfort can affect your topics of conversation, your mobility, and your sleep. All combine to make you increasingly unpleasant to be around. The more unpleasant you are, the less people want to hang with you. Fewer social interactions make you more susceptible to the problems we’ve been discussing. You become even more unable to interact socially, and people quit visiting. This cycle repeats itself over and over again: the lonelier you are, the lonelier you become. And that’s when the attack dog of depression strikes. By the time people are in their eighties, loneliness is the single greatest risk factor for clinical depression. That’s a steaming bag of bad neural news, as we’ll discuss in a later chapter.
The most dramatic effect of social isolation on the elderly is death. The probability of death is 45 percent greater for lonely seniors than it is for socially active ones. That number holds steady even when you control for things like debilitating physical ailments and depression. If you don’t have a lot of friends, you die sooner than you have to.
Inflammation of the brain
“Tell us, Mrs. Holderness, what do you think is the best thing about being 103?” a journalist asked. Molly’s response was quick and good-humored: “No peer pressure.”
She is fortunate to have a sharp mind. Many elderly people don’t—and most of those are women. Neuroscientist Laura Fratiglioni wondered if there could be a connection between the fact that men die before women, leaving widows alone in life, and the fact that women suffer more dementia than men, especially after the age of eighty. Could isolation be the culprit? Fratiglioni determined there was indeed a correlation. Women who live alone, as well as those without strong social interactivity, are at much greater risk for dementia than those who live with someone or have sustained, close social interactions.
The brain mechanisms behind this disturbing finding were soon under active investigation. A clear, more causal picture has emerged: excessive loneliness causes brain damage.
This deserves a fuller explanation because it’s a really big thing to say. The biological machinery involves, of all things, the same mechanisms stimulated when you stub your toe.
You undoubtedly know about inflammation. You stub your toe and local infectious agents—like bacteria—sweep in to take advantage, launching their Lilliputian attacks. Your body responds with swelling, redness, profanity. The classic inflammatory response is supervised by many molecules, including ones called cytokines. The response usually doesn’t last very long; the cytokines do their job and, in a few days, destroy the unwanted bad actors. This is a case of acute inflammation.
There is another type of inflammation, however, related to stubbed toes and also involving cytokines, but more relevant to our story. It is called systemic or persistent inflammation, the key difference tucked into its name: it lasts a long time. This type of inflammation occurs all over the body. It’s akin to getting tiny toe-stubs throughout the major organ systems, then having your whole body react with systemic, low-intensity inflammation as a result.
Don’t let the phrase “low intensity” fool you. Systemic inflammation damages many types of tissue over a long period of time, the way acid rain eats into a forest. It can even damage the brain, particularly white matter. White matter is composed of myelin sheaths that wrap around neurons, providing insulation to improve electrical performance. Without it, the brain doesn’t function very well.
How do you get systemic inflammation? The paths are many, including environmental factors such as smoking, exposure to pollution, or being overweight. Stress, ever the acid reflux of behavior, can incite it. And so can loneliness, according to Timothy Verstynen, director of the Cognitive Axon Lab at Carnegie Mellon University. He found in 2015 that chronic social isolation increases the level of systemic inflammation. Just how much damage loneliness causes in humans turns out to be astonishing. It’s at the same level as smoking. Or being too fat. The proposed molecular mechanism for this extraordinary observation is like a three-step feedback loop from geriatric hell: (1) loneliness causes systemic inflammation, (2) the inflammation damages white matter in the brain, and (3) the damage leads to the changes in behavior we mentioned, the ones resulting in fewer social interactions. Repeat.
If there is that thin a membrane between loneliness and brain damage, we have some serious thinking to do about how society treats its seniors. And how seniors treat themselves. We need to spend some quality time being grateful for the friends we have, and if the friendship tank is low, we need to seriously strategize about how to refill it.
A cultural shift
Refilling your friendship tank can be tough to do as you age. Researchers know you increase the quantity of friends you have in life until about age twenty-five. Then the number begins a long, slow decline, a deterioration that won’t stop until late into middle age. Baby boomers are notorious for losing friends in later life. As seniors, they have fewer social interactions with people of nearly every stripe—family members, friends, next-door neighbors—than seniors did in the previous generation.
Sociologists concur there are multiple reasons for this decrease, though not every researcher agrees on exactly what they are. Some point to the fact that people of child-bearing age move around a lot. This means communities are constantly being formed, uprooted, and re-formed—not a condition conducive to creating rich, long-lasting adult friendships. As a result, the guarantee of relational stability that comes from staying in one place gets torn up. My grandparents celebrated the multi-decade wedding anniversaries of friends with whom they had also shared a first-grade classroom. Such a thing is almost beyond imagining today.
It doesn’t help that people in developed countries are having fewer children than a generation ago. Over time, this means fewer uncles, aunts, and cousins. Even though that also means fewer annoying family reunions to attend, it shrinks the probability of sustaining long-term relationships with relatives (even if you did stay in one place). So you don’t have close friends. You don’t have