Successful Aging: A Neuroscientist Explores the Power and Potential of Our Lives

by Daniel J. Levitin

Exercising on a treadmill is good. Walking around the neighborhood is better. Walking in nature is the best.

One of the functions of sleep is to process the most emotionally intense experiences of the previous day, to separate the facts from our feelings so that we can reach a quasi-objective view of things. The other reason for doing so is so that the emotions themselves can be entered into and stored in memory. It is of value to be able to access a memory based not just on a particular time or a particular place (which we can all do), but also on a particular emotion.

The act of living and staying awake, going about our business, leads to a buildup of toxins in the blood and brain. Cerebrospinal fluid circulates throughout the brain and spinal cord, and it clears away toxins through a series of channels (like waterways) that expand during sleep. Almost none gets cleared away while you are awake. Why all this happens better during sleep than during wakefulness is not fully understood. Too little sleep, or—perhaps counterintuitively—too much sleep, impairs problem solving, attention to detail, memory, motivation, and reasoning.

sleep deprivation is now strongly associated with Alzheimer’s. Alzheimer’s disease occurs when a certain kind of protein, amyloid, builds up in the brain, where it forms clumps that collect between neurons, which in turn disrupt cell function. During proper, restorative sleep, these amyloid deposits get cleaned out of the brain through the action of the cerebrospinal fluid. When you’re sleep-deprived—either from short duration or poor-quality sleep—these amyloid deposits don’t get cleaned out, and they tend to selectively attack regions in the brain responsible for sleep, which then makes it even more difficult to sleep and, consequently, more difficult to clear out the amyloids.

It is becoming clear that a lack of sleep, particularly a chronic lack, can lead to Alzheimer’s disease.

We sleep in roughly ninety-minute cycles, comprising stages that are neurochemically and electrophysiologically distinctive. You’ve probably heard of the two kinds of sleep, REM and non-REM.

REM sleep helps us to maintain emotional balance. And a lot of what happens during REM sleep is simply random neural firing that has no particular meaning. Non-REM sleep is when our memories of the previous day are consolidated and linked with previous experiences.

changes in sleep biology accompany aging as well. The causes of sleep disruptions in older adults include a decreased amplitude of the circadian rhythms generated by the SCN (the timekeeper in the brain that maintains circadian rhythms), the degradation of neural signaling in the aging brain, and impairments in melatonin production. More than 40 percent of people over sixty-five report sleep problems. Nighttime sleep is often interrupted by frequent awakenings (sleep fragmentation); these interruptions become more frequent in the early-morning hours, and it can become more and more difficult to get back to sleep. With increasing age, the essential slow-wave sleep stage, a phase of non-REM sleep, is reduced, and early-night REM sleep increases.

With aging, men undergo a kind of menopause called andropause, concomitant with reductions in testosterone levels. This can lead to hot flashes, night sweats, enlarged breasts (gynecomastia), loss of strength, memory impairment, depression, cognitive decline, changes in sexual function, and disruptions in sleep.

Caffeine breaks down in the body to paraxanthine (80 percent) and to theophylline and theobromine (16 percent). Theophylline is also present in tea, and theobromine is present in chocolate. Adenosine is a somnogen—a sleep-promoting chemical in the body. The stimulant effects of caffeine and its metabolites (theophylline and theobromine) occur because they block adenosine receptors in the brain, and this blockage promotes sleeplessness.

Melatonin is a naturally occurring hormone in the body, secreted by the pineal gland during the dark hours of the day, typically a couple of hours before bedtime. It is also produced in other parts of the body. In the retina it is believed to have protective effects on photoreceptors. In bone marrow, it functions as a scavenger of free radicals and enhances immune function, reducing oxidative damage and protecting against iron overload and deterioration in these highly vulnerable cells. In the gastrointestinal tract, melatonin heals and protects against disorders and is being used experimentally as a treatment for gastric cancer, reflux esophagitis, peptic ulcers, ulcerative colitis, and intestinal ischemia/reperfusion. Melatonin is also widely found in the plant kingdom, where it regulates day-night bio-cycles and acts as a scavenger of free radicals. In tomatoes, for example, it helps to protect the components of photosynthesis. In peas and red cabbage that are grown in copper-contaminated soil it enhances their tolerance and survival rates. This makes melatonin a very old chemical compound that, through evolutionary history, found expanded functionality in mammals.

“Your body produces melatonin naturally. It doesn’t make you sleep, but as melatonin levels rise in the evening it puts you into a state of quiet wakefulness that helps promote sleep.”

Given the time-dependent nature of hormonal release schedules that are governed by the circadian clock, what is the most important thing about sleep? To go to bed at the same time every night and wake up at the same time every morning. Even on weekends.

write a quick to-do list for tomorrow. Worrying about incomplete future tasks is a significant contributor to difficulty falling asleep.

Among modern humans, 90 percent of deaths overall are from cancer and cardiovascular disease.

So-called blue zones made headlines in 2008 when demographers discovered the four places in the world that had the highest number of people over age one hundred: Nicoya, Costa Rica; Sardinia, Italy; Ikaria, Greece; and Okinawa, Japan (some lists add Del Mar, California).

assortative mating. When selecting a mate, most of us tend to be most comfortable with someone who is somewhat like us in terms of physical attractiveness, intellect, sociability, and other traits. That means that we’re choosing people who possess some genes similar to ours, even though we are not closely related.

removing part of the worms’ gonadal systems could extend their lives significantly. This parallels a finding that castrated men tend to live an average of fourteen years longer than uncastrated men who are similar on all other factors—and the younger they were when castrated, the longer the life span extension, in some cases up to twenty years. Italian castrati were also reputed to live longer. The connection between gonads and aging is not yet understood. It clearly involves something more than testosterone—probably something more fundamental—because the worms don’t have testosterone (although exposing them to it can cause adverse neural changes).

the limit to human cell division was between forty and sixty cell divisions, or replications (the Hayflick limit is usually cited as fifty).

70–80 percent of findings in science that industry tries to translate to drugs or therapies just don’t work. They worked in one particular cell line in the lab, or one particular set of people. We’ve seen a history of faulty translation. For example, “low fat!” That was a boon for the food industry; less fat, less calories, you can eat more. The current obesity epidemic is a direct result of that faulty translation.

aging is typically accompanied by loss of dopamine receptor neurons in the brain, and it is believed that this is partly responsible for the cognitive decline we observe, including the finding that older adults are especially disadvantaged when fast and efficient processing in novel situations is required.

To a neuroscientist, nicotine is in many ways the perfect drug for cognitive enhancement. It increases vigilance, attention, focus, memory, and creativity, and it refines motor skills, all without causing the jitters or stress that usually accompany stimulants—in fact, it tends to reduce stress. In particular, nicotine enhances attention by deactivating areas of the default mode, such as the posterior cingulate. It is being considered as a treatment for late-life depression and Parkinson’s disease and Alzheimer’s disease, where it is believed to have neuroprotective effects. Scientific American touted nicotine as the next smart drug. The problem with nicotine is that the most common delivery systems, smoking and chewing, cause cancer. Even with other delivery systems, such as gum, patches, and the new mouth sprays, it is highly addictive. It can increase heart rate, blood pressure, and inflammation, it can cause nausea, and in rodents it promotes cancer growth. In large doses nicotine is a poison, an evolutionary adaptation in the leaves of the tobacco plants to prevent insects from eating it. Humans can tolerate it in small doses, however, and if you get the dose right, you might get the benefits without the drawbacks. To minimize the possibility of addiction, it’s best to use it occasionally, for focus and energy, and not for more than a few days in a row.

senescence is the cumulative effect of things that happen to our bodies over time that may be harmful or cause difficulties for us. Cellular senescence is the specific case of our cells losing the ability to repair themselves and replicate. Much of what we recognize as the undesirable effects of aging is caused by cellular senescence—wrinkles, memory loss, and a lowered immune-system response. This is paralleled by a progressive decline in the ability of most organs to repair and recover from injury and disease. Many—perhaps most—older adults are living with chronic low-grade inflammation and decreased immune-system function. The majority of studies suggest that this inflammation is due to hormone deprivation (estrogen and testosterone).

Meditation reduces activity within the default mode network and increases connectivity between it and regions of the brain that are implicated in cognitive control—that is, controlling our thoughts: the dorsal anterior cingulate and dorsolateral prefrontal cortices. The result is that meditation simultaneously turns down the default mode’s pull on our attention, while streamlining and honing the network. Increased connectivity between the prefrontal region and the default areas also has an anti-inflammatory effect by reducing cytokines.

A handful of other pilot studies support the finding that meditation seems to have epigenetic effects. Loneliness triggers higher levels of pro-inflammatory genes; meditation can both lower those levels and decrease feelings of loneliness,

story of Gregory Aune, who was treated for Hodgkin’s lymphoma at age sixteen with a combination of drugs and radiation. He saw many of the patients in his ward die. Now forty-six, he has had to deal with hypothyroidism, diabetes, skin cancer, infertility, open-heart surgery, and a stroke, all tied to the treatments he received. Now a pediatric oncologist, he is pushing for more awareness of the aftermath. “The toxicity of the treatment has hung with me,” he says.

Happiness tends to decrease beginning in the late thirties (midlife crisis, anyone?) and then begins to increase sharply after age fifty-four. This holds true across seventy-two countries, from Albania to Zimbabwe.

One possibility is the disappointment of unrealized expectations. In our naïve twenties and thirties, our hopes are high, our scenarios rosy. Then reality trickled in like a slow leak in the roof. Only one person gets to be CEO—and it’s not going to be you. Some marriages crumble—and yours, sadly, is one of them. . . . Yet we don’t remain in the emotional basement for long, because over time we adjust our aspirations and later realize that life is pretty good. In short, we dip in the middle because we’re lousy forecasters. In youth, our expectations are too high.

perceived quality of life is more important to an individual’s well-being than objective measures of quality of life.

Social comparison theory states that our life satisfaction tends to be influenced not so much by what we have but by what we have in relation to others. That is, we look to see how others are living, such as whether they have shoes or have fewer aches and pains—and we judge ourselves in comparison. We are a social species, and we are attuned to fairness. If we see others who have things we don’t, like shoes or good health, we feel cheated. If no one we know has shoes or good health, we just think to ourselves, “That’s life.”

Aristotle’s principle of the golden mean (neither too much nor too little of a thing).

good relationships keep us happy and healthier, period . . . social connections are really good for us . . . loneliness kills. People who are more socially connected to family, to friends and community, are happier, healthier, and they live longer. And loneliness turns out to be toxic. . . . High conflict marriages without much affection are very bad for our health—worse than getting divorced.

A person could have a successful career, money, and good physical health, but without supportive, loving relationships, they won’t be happy. Men’s relationships at age forty-seven, the researchers found, predicted late-life adjustment better than any other variable, except ability to cope with setbacks (what he called defense mechanisms). Good sibling relationships loomed especially powerful: 93 percent of the men who were thriving at age sixty-five had been close to a brother or sister when younger. “It is social aptitude,” wrote George Vaillant, who directed the study for three decades, “not intellectual brilliance or parental social class, that leads to successful aging.” Asked what he had learned after thirty years of studying the cohort, Vaillant was clear: “That the only thing that really matters in life are your relationships to other people.”

people who divorce are not, as a group, malcontents who can’t work things out. In the 1960s and ’70s, many researchers thought that divorce was caused by personality disorders, poor coping style, passive aggression, acting out, aggression, and alcohol abuse. But that has not been borne out by research. Marriages fail for a variety of reasons, and often the simplest explanation is the most accurate: The couple were merely mismatched and didn’t realize it until later.

Politics appears to correlate with late-life happiness as well, at least insofar as sex is concerned: Aging liberals have more sex, according to the Harvard study. The most conservative men ceased sexual relations at an average age of sixty-eight, while the most liberal men had active sex lives into their eighties.

It’s not just social connections late in life that determine happiness and other measures of life satisfaction. Although they’re crucial, they occur in a context of a lifetime of social connections. Men who had “warm” childhood relationships with their mothers earned an average of $87,000 more a year than men whose mothers were uncaring. (Wow! Thanks, Mom!) Men who had poor childhood relationships with their mothers were much more likely to develop dementia when old. Late in their professional lives, the men’s boyhood relationships with their mothers—but not with their fathers—were associated with effectiveness at work. On the other hand, warm childhood relations with fathers correlated with lower rates of adult anxiety, greater enjoyment of vacations, and increased “life satisfaction” at age seventy-five—whereas the warmth of childhood relationships with mothers had no significant bearing on life satisfaction at seventy-five.

according to the US Census, the divorce rate for couples over sixty-five has tripled in the last twenty-five years.

Between 25 and 40 percent of people who retire reenter the workforce. Harvard economist Nicole Maestas says, “You hear certain themes: a sense of purpose. Using your brain. And another key component is social engagement.” Recall Sigmund Freud’s words that the two most important things in life are to have love and meaningful work.

If the environment can modify gene expression-epigenetics, then it stands to reason that the context within which a person lives is not only important, but critical to understand.

The ability to be spontaneous is key to feeling as though you are an author of the script of your own life.

social isolation is one of the biggest risk factors for older adults. A vital social community—someone nearby you can call up and go to lunch with once in a while—can make all the difference.

What we can all do now is to be more intentional and mindful of how we live in the world. Remain Curious and mentally engaged. Be Open to new experiences. Keep up your social Associations. Try to be Conscientious. Follow the Healthy lifestyle practices I’ve described regarding diet, exercise, and good sleep hygiene.

The single most important factor in determining successful aging is the personality trait of Conscientiousness. Conscientiousness is associated with a great number of positive outcomes in life. As I wrote in the first chapter, the fields of psychiatry and clinical psychology are predicated on the premise that you can change; you can will yourself or train yourself to be more conscientious, even later in life, and the benefits will still accrue to you. The latest science seems to confirm what has been argued, for millennia, by various forms of religion—that personality is malleable and one can learn to interact with the world in new ways, even well into one’s eighties and beyond.

The second most important factor in retaining mental vitality later in life is to exercise in varied, natural environments. You don’t need to run marathons. Power walking in a park or forest, fast enough to get your heart rate up and your brain full of rich, oxygenated blood, is the goal. The varied environment will stimulate your brain and in particular the hippocampus, the seat of memory. And the thousands of little microadjustments you need to make to your gait, the angle of your feet, and maintaining your balance and pace will exercise the circuits in your brain that evolved to adapt to the environment. Adapting to new things, especially in the physical world, strengthening the visual-motor-kinesthetic circuits in your brain, can make an enormous difference in fending off cognitive decline.

The third most important factor is social interaction. Interacting with others is among the most complex things we can do with our brains. It could be through playing music with them, playing bridge or golf, acting in community theater, reminiscing, or discussing literature in a book group. Nearly every part of our brains is activated by interacting with others, live, face-to-face, in real time. (Sorry, Skype.) Doing so requires us to read their body language, the emotions in their faces, and the contours of their speech.

A good strategy for life, at any age, is to let go of grievances, both petty and large. Don’t spend your life hating and being angry. As former U.S. senator Alan Simpson (age eighty-eight) says, “Hatred corrodes the container in which it is carried.”

Practice gratitude for what you have. This is motivating, alters brain chemistry toward more positive emotions, and oils the pleasure circuits of the brain. It can be as simple as appreciating the taste of your morning coffee or the sunlight peeking through the window. Gratitude is a powerful mind-set. As Walt Whitman wrote, Happiness . . . not in another place . . . but this place, not for another hour but this hour.

By 2030 there will be more individuals in the United States over sixty-five than under fifteen years of age. It’s been estimated that two-thirds of the people over sixty-five who have ever lived are alive today, and three-quarters of the people over seventy-five who have ever lived are alive today.

REJUVENATING YOUR BRAIN Don’t retire. Don’t stop being engaged with meaningful work. Look forward. Don’t look back. (Reminiscing doesn’t promote health.) Exercise. Get your heart rate going. Preferably in nature. Embrace a moderated lifestyle with healthy practices. Keep your social circle exciting and new. Spend time with people younger than you. See your doctor regularly, but not obsessively. Don’t think of yourself as old (other than taking prudent precautions). Appreciate your cognitive strengths—pattern recognition, crystallized intelligence, wisdom, accumulated knowledge. Promote cognitive health through experiential learning: traveling, spending time with grandchildren, and immersing yourself in new activities and situations. Do new things.