It’s all downhill from here

Your brain starts shrinking at 25. Your handshake starts going soft at 30. At 40, your memory starts to slip. In a new book, author David Shields catalogues the myriad ways that our bodies gradually betray us.

If you could live forever in good health at a particular age, what age would you be? As people get older, their ideal age gets higher. For 18- to 24-year-olds, it’s age 27; for 25- to 29-year-olds, it’s 31; for 40- to 49-year-olds, it’s 40; and for people over 64, it’s 59.

Your strength and coordination peak at 19. Your body is the most flexible until age 20; after that, joint function steadily declines. World-class sprinters are almost always in their late teens or early 20s. Your stamina peaks in your late 20s or early 30s; marathon records are invariably held by 25- to 35-year-olds.

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Sir William Osler, the father of modern medicine, said, “The effective, moving, vitalizing work of the world is done between the ages of 25 and 40.” Which is in fact true: Creativity peaks in the 30s, then declines rapidly; most creative achievements occur when people are in their 30s. Degas said, “Everyone has talent at 25; the difficulty is to have it at 50.” The consolation of the library: When you’re 45, your vocabulary is three times as large as it is at 20. When you’re 60, your brain possesses four times the information than it does at 20.

Your IQ is highest between ages 18 and 25. Once your brain peaks in size—at age 25—it starts shrinking, losing weight, and filling with fluid. As you age, your responses to stimuli of all kinds become slower and more inaccurate, especially in more complex tasks. From ages 20 to 60, your reaction time to noise slows 20 percent. At 60, you make more errors in verbal learning tasks. Given a list of 24 words, an average 20-year-old remembers 14 of the words, a 40-year-old remembers 11, a 60-year-old remembers nine, and a 70-year-old remembers seven.

Most people reach skeletal maturity by their early 20s. At 30, you reach peak bone mass. Your bones are as dense and strong as they’ll ever be. In your late 30s, you start losing more bone than you make. At first you lose bone slowly, 1 percent a year. The older you get, the more you lose.

Beginning in your early 20s, your ability to detect salty or bitter things decreases, as does your ability to identify odors. The amount of ptyalin, an enzyme used to digest starches, in your saliva decreases after age 20. After age 30, your digestive tract displays a decrease in the amount of digestive

juices. At 20, in other words, your fluids are fleeing, and by 30, you’re drying up.

Lauren Bacall said, “When a woman reaches 26 in America, she’s on the slide. It’s downhill all the way from then on. It doesn’t give you a tremendous feeling of confidence and well-being.”

Until you’re 30, your grip strength increases; after 40, it declines precipitously. After age 65, your lower arm and back muscle strength declines. Owing to reduced coordination rather than loss of strength, your power output—e.g., your ability to turn a crank over a period of time—falls after age 50.

By age 35, nearly everyone shows some of the signs of aging, such as graying hair, wrinkles, less strength, less speed, stiffening in the walls of the central arteries, degeneration of the heart’s blood vessels, diminished blood supply to the brain, elevated blood pressure. The maximum rate your heart can attain is your age subtracted from 220; therefore it falls by one beat every year. Your heart is continually becoming a less-efficient pumping machine.

Emerson said, “After 30, a man wakes up sad every morning, excepting perhaps five or six, until the day of his death.”

In My Dinner With André, Wallace Shawn says, “I grew up on the Upper East Side, and when I was 10 years old I was rich, an aristocrat, riding around in taxis, surrounded by comfort, and all I thought about was art and music. Now I’m 36, and all I think about is money.”

Mozart died at 35; Byron, at 36; Raphael and van Gogh, at 37. The oldest age at which anyone broke a track-and-field record was 41, in 1909.

Beginning at 40, your white blood cells, which fight cancer and infectious diseases, have a lowered capacity. Each year, more fat gets deposited in the walls of medium and larger arteries, causing the arterial walls to narrow. The weight of your small intestine decreases; the volume and weight of your kidneys shrink. Total blood flow to the kidneys decreases by 10 percent for every decade after the age of 40. Every organ will eventually get less nourishment than it needs to do its job.

Cicero said, “Old age begins at 46.” He died at 53.

Victor Hugo said, “Forty is the old age of youth. Fifty is the youth of old age.”

Every decade after age 50, your brain loses 2 percent of its weight. You have difficulty learning things and you remember less and less. Memory per se—the actual encoding of information—isn’t diminished in a healthy, older person, but retrieval can be an excruciatingly slow process and take many more attempts. Older people are more susceptible to distraction, have trouble coordinating multiple tasks, and have decreased attention spans. In simple tasks and common situations, the old do fine, but when exercise or other stress is added, they often struggle. Perhaps this is why some older people, finding it harder to cope, tend to start searching for comfort rather than excitement.

Evelyn Waugh said, “Old people are more interesting than young. One of the particular points of interest is to observe how after 50 they revert to the habits, mannerisms, and opinions of their parents, however wild they were in youth.”

“At 50, everyone has the face he deserves,” said George Orwell.

Virgil, author of The Aeneid, died at 50. Shakespeare died at 52.

You gain weight until age 55, at which point you begin to shed weight (specifically, lean tissue, muscle mass, water, and bone). More fat now accumulates in your thighs and less in your abdomen. Your extremities become thinner and your trunk thicker. Middle-aged spread isn’t only the result of increased fatty tissue; it’s also caused by losing muscle tone and your skin literally thinning out as each skin cell loses its robustness.

In late middle age, the skin in your hands becomes less sensitive to touch. Your skin cells regenerate less often. The skin weakens and dries, the number of sebaceous glands declines dramatically, and all of the tissues of the skin undergo some change: You get wrinkles and gray hair. Wrinkles don’t come from age, though. They come from sunlight, which slowly maims the face, causing wrinkles, mottling, and loose skin. “The years between 50 and 57 are the hardest,” said T.S. Eliot. “You are being asked to do things, and yet you are not decrepit enough to turn them down.”

Your blood cholesterol increases. At 60, you’ve lost 25 percent of the volume of saliva you normally secrete for food; it becomes more difficult to digest heavy meats.

Emerson said, “’Tis strange that it is not in vogue to commit hara-kiri, as the Japanese do, at 60. Nature is so insulting in her hints and notices, does not pull you by the sleeve, but pulls out your teeth, tears off your hair in patches, steals your eyesight, twists your face into an ugly mask, in short, puts all contumelies upon you, without in the least abating your zeal to make a good appearance, and all this at the same time that she is moulding the new figures around you into wonderful beauty, which of course is only making your plight worse.”

The PR flak Harlan Boll defends his lying about his celebrity clients’ ages by saying, “The American public doesn’t really forgive people for getting older.” Which is of course true. Jackie Kennedy said if she knew she was going to get cancer at 65, she wouldn’t have done all those sit-ups. In jail, O.J. Simpson bemoaned to his girlfriend that the once admirable, apple-like shape of his posterior had collapsed into middle-aged decrepitude. Gravity sucks.

By the time you reach 65, you’ve lost 30 percent to 40 percent of your aerobic power. The walls of your heart thicken, and you’re more likely to develop coronary disease. Sixty percent of 60-year-old men, and the same percentage of 80-year-old women, have a major narrowing in at least one coronary artery. A stiffening in the walls of the major arteries results in a progressive increase in blood pressure, which imposes an increasing load on the heart. Since the heart has to work harder for each heartbeat and use more energy, the overall efficiency of the cardiovascular system drops significantly.

When you’re a young adult, the reflex that tells you it’s time to urinate occurs when your bladder is half-full. For people over age 65, the message isn’t received until your bladder is nearly full.

At 68, Edmund Wilson said, “The know­ledge that death is not so far away, that my mind and emotions and vitality will soon disappear like a puff of smoke, has the effect of making earthly affairs seem unimportant and human beings more and more ignoble. It is harder to take human life seriously, including one’s own efforts and achievements and passions.”

In your late 60s, you eat less. Your metabolic rate decreases slightly. The density of your skin’s circulatory systems—veins, capillaries, arterioles—is reduced, which is why old people feel cold sooner. Also, your skin functions less well as a barrier because the skin is thinner—like wearing too light a coat. As you age, your facial skin temperature falls. For older people, a comfortable temperature is 10 to 15 degrees higher than it is for a younger person.

There are now more people in the United States over 65 than ever before. Only 30 percent of people ages 75 to 84 report disabilities—the lowest percentage ever reported.

Five percent to 8 percent of people over 65 have dementia; half of those in their 80s have it.

Aristotle described childhood as hot and moist, youth as hot and dry, and adulthood as cold and dry. He believed aging and death were caused by the body being transformed from one that was hot and moist to one that was cold and dry—a change that he viewed as not only inevitable but desirable.

At age 90, you grow increasingly less likely to develop cancer; the tissues of an old person don’t serve the needs of aggressive, energy-hungry tumors.

When you’re very young, your ability to smell is so intense as to be nearly overwhelming, but by the time you’re in your 80s, not only has your ability to smell declined significantly but you yourself no longer even have a distinctive odor. You can stop using deodorants. You’re vanishing.

“As we get older,” the British poet Henry Reed helpfully observed, “we do not get any younger.”

From The Thing About Life Is That One Day You’ll Be Dead by David Shields. © 2008 by David Shields. Excerpted by permission of Knopf, a division of Random House, Inc.