The Body: A Guide for Occupants

by Bill Bryson

Among the most puzzling of headaches are migraines. Migraine (the word is a corruption of the French demi-craine, meaning “half the head”) affects 15 percent of people but is three times more common in women than in men. Migraines are almost wholly a mystery. They are highly individual. Oliver Sacks in a book on migraines described nearly one hundred varieties of migraine. Some people feel surprisingly wonderful before migraines. The novelist George Eliot said she always felt “dangerously well” just before a migraine started. Others are indisposed for days and left feeling starkly suicidal.

The United States has 4 percent of the world’s population but consumes 80 percent of its opioids. About two million Americans are thought to be opioid addicts.

The cost to the economy has been put at over $500 billion a year in lost earnings, medical treatments, and criminal proceedings.

Perversely, farming didn’t bring improved diets but almost everywhere poorer ones. Focusing on a narrower range of staple foods meant most people suffered at least some dietary deficiencies, without necessarily being aware of it. Moreover, living in proximity to domesticated animals meant that their diseases became our diseases. Leprosy, plague, tuberculosis, typhus, diphtheria, measles, influenzas—all vaulted from goats and pigs and cows and the like straight into us. By one estimate, about 60 percent of all infectious diseases are zoonotic (that is, from animals). Farming led to the rise of commerce and literacy and the fruits of civilization but also gave us millennia of rotten teeth, stunted growth, and diminished health. We forget

If you want to imagine what a disease might do if it became bad in every possible way, you could do no better than consider the case of smallpox. Smallpox is almost certainly the most devastating disease in the history of humankind. It infected nearly everyone who was exposed to it and killed about 30 percent of victims. The death toll in the twentieth century alone is thought to have been around 500 million. Smallpox’s astounding infectiousness was vividly demonstrated in Germany in 1970 after a youthful tourist developed it upon returning home from a trip to Pakistan. He was placed in hospital quarantine but opened his window one day to sneak a cigarette. This, it has been reported, was enough to infect seventeen others, some two floors away.

“The fact is,” he says, “we are really no better prepared for a bad outbreak today than we were when Spanish flu killed tens of millions of people a hundred years ago. The reason we haven’t had another experience like that isn’t because we have been especially vigilant. It’s because we have been lucky.”

Today some 40 percent of us will discover we have cancer at some point in our lives.

Many, many more will have it without knowing it and will die of something else first. Half of men over sixty and three-quarters over seventy, for instance, have prostate cancer at death without being aware of it. It has been suggested, in fact, that if all men lived long enough, they would all get prostate cancer.

They divide without limit. They grow without direction or influence from outside agents like hormones. They engage in angiogenesis, which is to say they trick the body into giving them a blood supply. They disregard any signals to stop growing.

They fail to succumb to apoptosis, or programmed cell death. They metastasize, or spread to other parts of the body.

Cancer cells are just like normal cells except that they are proliferating wildly. Because they are so seemingly normal, the body sometimes fails to detect them and doesn’t invoke an inflammatory response as it would with a foreign agent. That means that most cancers in their early stages are painless and invisible. It is only when tumors grow big enough to press on nerves or form a lump that we become aware that something is wrong. Some cancers can quietly accrete for decades before they become evident. Others never become evident at all.

Eighty percent of cancers, known as carcinomas, arise in epithelial cells—that is, the cells that make up the skin and the linings of organs. Breast cancers, for instance, don’t just grow randomly within the breast, but normally begin in the milk ducts. Epithelial cells are assumed to be particularly susceptible to cancers because they divide rapidly and often. Only about 1 percent of cancers are found in connective tissue; these are known as sarcomas.

Men face similarly unhappy prospects with prostate screening. The prostate is a small gland, about the size of a walnut and weighing just one ounce, which is chiefly involved in producing and distributing seminal fluid.

It is tucked neatly—not to say inaccessibly—up against the bladder and wrapped around the urethra like a neckerchief ring.

For about a decade, Hayflick’s findings languished. But then a team of researchers at the University of California at San Francisco discovered that stretches of specialized DNA at the end of each chromosome called telomeres fulfill the role of tallying device. With each cell division, telomeres shorten until eventually they reach a predetermined length (which varies markedly from one cell type to another) and the cell dies or becomes inactive. With this finding, the Hayflick limit suddenly became credible. It was hailed as the secret of aging. Arrest the shortening of telomeres and you could stop cell aging in its tracks. Gerontologists everywhere became very excited.

After the age of sixty, the risk of death doubles every eight years. A study by geneticists at the University of Utah found that telomere length may account for as little as 4 percent of that additional risk.

Aging, it turns out, not only involves much more than telomeres, but telomeres are involved in much more than aging. Telomere chemistry is regulated by an enzyme called telomerase, which switches off the cell when it has reached its preset quota of divisions. In cancerous cells, however, telomerase doesn’t instruct the cells to stop dividing, but rather lets them go on proliferating endlessly. This has raised the possibility that a way to fight cancer would be to target telomerase in the cells. In sum, it’s clear that telomeres are important not just for understanding aging but also for understanding cancer, but unfortunately we are still a long way from fully understanding either.

Two other terms encountered commonly, if no more productively, in discussions of aging are “free radicals” and “antioxidants.” Free radicals are wisps of cellular waste that build up in the body in the process of metabolism. They are a by-product of our breathing oxygen. As one toxicologist has put it, “The biochemical price of breathing is aging.” Antioxidants are molecules that neutralize free radicals, so the thinking is that if you take a lot of them in the form of supplements, you can counter the effects of aging. Unfortunately, there is no scientific evidence to support that.

The bad news is that menopause can be a terrible ordeal. Hot flashes are experienced by about three-quarters of women during menopause. (It is a feeling of sudden warmth, generally in the chest or above, induced by hormonal changes for unknown reasons.) Menopause is related to a fall in production of estrogen, but even now there isn’t any test that can definitively confirm the condition. The best indicators for a woman that she is entering menopause (a stage known as perimenopause) are that her periods become irregular and she is likely to find herself experiencing a “sense that things aren’t quite right,” as Rose George wrote for the Wellcome Trust publication Mosaic.

Menopause is as much a mystery as aging itself. Two principal theories have been advanced, known rather neatly as the mother hypothesis and the grandmother hypothesis. The mother hypothesis is that childbearing is dangerous and exhausting, and it becomes more of both as women age. So menopause may simply be a kind of protection strategy. By no longer having the wear and distraction of further childbirth, a woman can better focus on maintaining her own health while completing the rearing of her children just as they are entering their most productive years. This leads naturally to the grandmother hypothesis, which is that women stop breeding in middle age so that they can help their offspring raise their children. It is a myth, incidentally, that menopause is triggered by women exhausting their supply of eggs. They still have eggs. Not many, to be sure, but more than enough to remain fertile. So it isn’t the literal running out of eggs that triggers the process (as even many doctors appear to believe). No one knows exactly what is the trigger.

“The best way to assure longevity is to pick your parents.”

Some people live longer than they ought to by any known measures. As Jo Marchant notes in her book Cure, Costa Ricans have only about one-fifth the personal wealth of Americans, and have poorer health care, but live longer. Moreover, people in one of the poorest regions of Costa Rica, the Nicoya Peninsula, live longest of all, even though they have much higher rates of obesity and hypertension. They also have longer telomeres. The theory is that they benefit from closer social bonds and family relationships. Curiously, it was found that if they live alone or don’t see a child at least once a week, the telomere length advantage vanishes. It is an extraordinary fact that having good and loving relationships physically alters your DNA. Conversely, a 2010 U.S. study found, not having such relationships doubles your risk of dying from any cause.

We now know that Alzheimer’s begins with an accumulation of a protein fragment called beta-amyloid in the sufferer’s brain. Nobody is quite sure what amyloids do for us when they are working properly, but it is thought they may have a role in forming memories. In any case, they are normally cleared away after they have been used and are no longer needed. In Alzheimer’s victims, however, they aren’t flushed away but accumulate in clusters known as plaques and stop the brain from functioning as it should.

In its normal progression, Alzheimer’s first demolishes short-term memories, then moves on to all or most memories, leading to confusion, shortness of temper, loss of inhibition, and eventually loss of all bodily functions, including how to breathe and swallow. As one observer has put it, in the end “one forgets, on a muscular level, how to exhale.” People with Alzheimer’s, it could be said, die twice—first in the mind, then in the body.

The more education you have had, the less likely you are to get Alzheimer’s, though having an active and questing mind, as opposed to just racking up a lot of classroom hours in one’s youth, is almost certainly what keeps Alzheimer’s at bay.

Getting old is the surest route to dying. In the Western world, 75 percent of deaths from cancer, 90 percent from pneumonia, 90 percent from flu, and 80 percent from all causes occur in people sixty-five years of age or older.

According to a 2014 study in the Journal of Palliative Medicine, between 50 and 60 percent of terminally ill patients report having intense but highly comforting dreams about their impending passing. A separate study found evidence of a surge of chemicals in the brain at death, which may account for the intense experiences often reported by survivors of near-death incidents.

Most dying people lose any desire to eat or drink in the last day or two of life. Some lose the power of speech. When the ability to cough or swallow goes, they often make a rasping sound commonly known as a death rattle. It can sound distressing but seems not to be to those experiencing it. However, another kind of labored breathing at death, called agonal breathing, may very well be.

Agonal breathing, in which the sufferer can’t get enough breath because of a failing heart, may last only for a few seconds, but it can go on for forty minutes or more and be extremely distressing to both victim and loved ones at the bedside. It can be stopped with a neuromuscular blocking agent, but many doctors won’t administer it, because it inevitably hastens death and is there...

Death becomes apparent very quickly. Almost at once the blood begins to drain from the capillaries near the surface, leading to the ghostly pallor associated with death. “A man’s corpse looks as though his essence has left him, and it has. He is flat and toneless, no longer inflated by the vital spirit the Greeks called pneuma,” wrote Sherwin Nuland in How We Die. Even to someone unused to dead bodies, death is usually instantly recognizable.

Tissue deterioration starts almost at once, which is why “harvesting” (surely the ugliest term in medicine) organs for transplant is such an urgent business. Blood pools in the lowest parts of the body, as gravity demands, turning the skin there purple in a process known as livor mortis. Internal cells rupture and enzymes spill out and begin a self-digesting process known as autolysis. Some organs function longer than others. The liver will continue to break down alcohol after death, even though it has absolutely no need to do so. Cells, too, die at different rates. Brain cells go quickly, in no more than about three or four minutes, but muscle and skin cells may last for hours—perhaps a whole day. The famous muscle stiffening known as rigor mortis (literally “stiffness of death”) sets in between thirty minutes and four hours after death, starting in the facial muscles and moving downward through the body and outward to the extremities. Rigor mortis lasts for a day or so.