The peak age for asthma onset is thirteen, but large numbers of people first experience it in adulthood. “Doctors will tell you that the first few years of life are crucial for asthma, but that’s not exactly true,” says Pearce. “It’s the first few years of exposure. If you change jobs or change countries, you can still get asthma even as an adult.”
Some years ago, Pearce made a curious discovery—that people who had had a cat early in life seemed to derive lifelong protection from getting asthma. “I like to joke that I’ve studied asthma for thirty years and I have never prevented a single case, but I have saved the lives of a lot of cats,” he says.
In what way exactly Western lifestyles might provoke asthma isn’t easy to say. Growing up on a farm seems to protect you, and moving to the city increases your risk, but once again we don’t really know why. One intriguing theory, suggested by Thomas Platts-Mills of the University of Virginia, links asthma increases with children spending less time running around outdoors. As Platts-Mills has noted, children used to play outside after school. Now more often than not they go indoors and stay there. “We now have a population that sits around the house and sits still in ways that children have never sat still before,” he told the journal Nature. Children who sit watching television not only are not exercising their lungs as they would if they were at play but even breathe differently from children who are not transfixed by a screen. Specifically, children who are reading take deeper breaths and sigh more often than children watching TV, and that slight difference in respiratory activity may be enough to increase TV watchers’ susceptibility to asthma, according to this theory.
Other researchers have suggested that viruses may be responsible for asthma onset. A study at the University of British Columbia in 2015 suggested that an absence of four gut microbes (namely, Lachnospira, Veillonella, Faecalibacterium, and Rothia) in infants was closely associated with the development of asthma in the first years of life. But so far all these are just hypotheses. “The bottom line is that we just don’t know yet,” says Pearce.
III
ONE OTHER ALL-TOO-COMMON affliction of the lungs deserves a mention, not so much because of what it does to us as because of how extraordinarily long it took us to accept that it was doing it. I refer to smoking and lung cancer.
It would seem almost impossible to ignore a link between the two. A person who smokes cigarettes regularly (about a pack a day) is fifty times more likely than a nonsmoker to get cancer. In the thirty years between 1920 and 1950, which is when cigarette smoking took off in a big way in the world, the number of lung cancer cases soared. In America, they tripled. Similar increases were noted elsewhere. Yet it took forever to gain consensus that smoking caused lung cancer.
It seems crazy to us today, but it wasn’t so crazy to people back then. The problem was that huge proportions of people smoked—80 percent of all men by the late 1940s—yet only some of them developed lung cancer. And some people who didn’t smoke also developed lung cancer. So it was not especially straightforward to see a direct link between smoking and cancer. When lots of people are doing something and only some of them are dying from it, it makes it hard to impute blame to a single cause. Some people blamed air pollution for the rise of lung cancer. Others suspected the increased use of asphalt as a paving surface.
One leading skeptic was Evarts Ambrose Graham (1883–1957), a chest surgeon and professor at Washington University in St. Louis. Graham famously (but facetiously) maintained that we might as plausibly blame lung cancer on the development of nylon stockings because they had become popular at the same time as smoking. But when a student of his, the German-born Ernst Wynder, sought permission to conduct a study on smoking and cancer in the late 1940s, Graham gave his consent, mostly in the expectation that it would disprove the theory of a link between smoking and cancer once and for all. In fact, Wynder demonstrated conclusively that there was a link—so much so that Graham was persuaded by the evidence to change his mind. In 1950, the two men published a joint paper in The Journal of the American Medical Association outlining a clear statistical link between smoking and lung cancer. Soon afterward, the British Medical Journal ran a study with more or less identical findings by Richard Doll and A. Bradford Hill of the London School of Hygiene and Tropical Medicine.*1
Although two of the world’s most prestigious medical journals had now demonstrated a clear association between smoking and lung cancer, the findings had almost no effect. People just loved smoking too much to quit. Richard Doll in London and Evarts Graham in St. Louis, both lifelong smokers, quit tobacco, but too late in the case of Graham. He died of lung cancer seven years after his own report. Elsewhere smoking just kept rising. The volume of smoking in the United States increased by 20 percent in the 1950s.
Spurred on by the tobacco industry, many commentators mocked the findings. Because Graham and Wynder could hardly train mice to smoke, they developed a machine that would extract tar from smoked cigarettes, which they then daubed on the skin of laboratory mice, causing tumors to erupt there. A writer from Forbes magazine wondered acidly (and, it must be said, a touch imbecilically), “How many men distill their tar from their tobacco and paint it on their backs?” Governments took little interest in the question. When Britain’s minister of health, Iain Macleod, formally announced at a press conference that there was an unequivocal connection between smoking and lung cancer, he rather undercut his position by smoking conspicuously as he did so.
The Tobacco Industry Research Committee—a scientific panel paid for by cigarette manufacturers—argued that although cancer from tobacco had been induced in laboratory mice, it had never been demonstrated in humans. “No one has established that cigarette smoke, or any one of its known constituents, is cancer-causing to man,” wrote the panel’s scientific director in 1957, conveniently overlooking that there could never be an ethical way to experimentally induce cancer in a living person.
To further obviate concerns (and to make their products more appealing to women), cigarette manufacturers introduced filters in the early 1950s. Filters had the great effect that they could claim their cigarettes were now much safer. Most manufacturers charged a premium price for filtered cigarettes, even though the cost of filters was less than the tobacco they displaced. Moreover, most filters didn’t filter out tars and nicotine any better than the tobacco itself had, and to compensate for a perceived loss of taste, the manufacturers started using stronger tobacco. The upshot was that by the late 1950s the average smoker was taking in more tar and nicotine than he had before filters were invented. By this point, the average American adult was smoking four thousand cigarettes a year. Interestingly, quite a lot of valuable cancer research in the 1950s was done by scientists funded by the cigarette industry who were urgently searching for causes of cancer other than cigarettes. As long as tobacco wasn’t directly implicated, their research was often impeccable.