April 18, 2024
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April 18, 2024
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Tobacco and Cancer: Part I

We are all aware of the profound effect that cigarette smoking has had on the incidence and mortality of cancer. The best estimates are that tobacco is responsible for about one third of cancer—not just lung cancer, but other cancers of the upper aerodigestive tract (oral cavity, larynx, head and neck, esophagus), bladder, kidney, pancreas and even colon. And aside from cancer, tobacco is a major contributor to coronary artery disease, strokes, and chronic obstructive pulmonary disease.

Tobacco was a native plant of the New World and became a major cash crop of the British colonies; it has thus been available for centuries. Nonetheless, these diseases were present but uncommon until the beginning of the 20th century, when their incidence skyrocketed.

What changed then? Basically, two things—the tobacco companies began mass-producing cigarettes in their current form and in packs. Prior to 1900, if you wanted to smoke a cigarette, you needed to have tobacco paper and a tobacco pouch, and roll your own. This change made cigarettes cheap and easily consumable in large quantities.

A second major event was the onset of World War I, during which the Red Cross and other agencies, out of benevolence, distributed cigarettes to the young fighting men and thereby addicted a generation of males; this phenomenon was repeated a generation later during World War II. The end result was that by 1950, 80-85% of U.S. men were smokers. (Women only started to catch up during the 1960s with the advent of the feminist revolution.)

Clearly, the most salient increase was in lung cancer, which rose dramatically over the first half of the 20 century. This increase did not go unnoticed by the medical profession—it was profound. And yet except for a random paper here and there by lonely voices, with little or no direct evidence to back them up, the idea that cigarette smoking, which was rising in tandem with the lung cancer epidemic, might be related or responsible, was almost totally missed. Of course, the late 1930s and 1940s had a lot going on and the major scientists and thinkers were surely occupied with other concerns.

Nonetheless, if you were a cancer researcher in 1949, what exactly might you have thought was responsible for the rise in lung cancer? I can only speculate, but the possibilities seem as follows:

1. Probably the leading theory was that some yet-unidentified microorganism was responsible. We must remember that the 19th and early 20th centuries had been extraordinarily successful in addressing many important diseases with this approach, and it was reasonable to assume that some microorganism might be at the heart of lung cancer as well.

2. Another strong possibility was that increasing air pollution was causing the lung cancer increase. Again, not a ridiculous idea. In fact, air pollution does increase the risk for lung cancer, though not at the rates that were being experienced.

3. Occupational exposures were also put forward as contributors—that would have explained the male-female differences, though this would not have explained the very wide distribution of the disease.

4. Finally, what I would call decreasing competing causes of mortality. Basically, a man born in 1900 had a life expectancy of about 46, mostly due to infectious diseases that we no longer think about because of vaccinations, a clean water supply, improved maternal and child health, and sterile surgical practices. By the time FDR instituted Social Security in the early 1930s, life expectancy had risen to 62, and it is now hovering around 80. Researchers in that time period might have seen the rise of these chronic diseases—lung cancer and other cancers of middle and older ages, heart disease, stroke—as just part of the aging process without recognizing the need to attribute them to some other factor.

Remember, we were still in the era of infectious disease epidemiology. Chronic disease epidemiology in which we began to investigate the genetic, environmental and lifestyle causes of these chronic diseases had not yet made its appearance. Jim Watson and Francis Crick’s discovery of DNA was in the early 1950s. It was not obvious to the routine or casual observer that diseases like heart disease or cancer had “causes” as we know them.

If you think this is odd, consider for a moment how we think about the elderly and dementia. We consider its organic cause—multi-infarct, Alzheimer’s, Parkinson’s, etc.—but we accept it as a natural part of aging. Perhaps 50 years from now or much sooner we will also be understanding what common factor(s) lead to this problem that we are currently unaware of.

Amazingly enough, 1950 was the year that chronic disease epidemiology had its true birth, and while many scientists played a major role in this, most notably statisticians and epidemiologists in the U.K. and the Commonwealth, the true landmark event that took place in early 1950 was the work of a Jewish refugee from Nazi Germany. Come back next week to “Thoughts on Cancer.”

Alfred I. Neugut, MD, PhD, is a medical oncologist and cancer epidemiologist at Columbia University Irving Medical Center/New York Presbyterian and Mailman School of Public Health in New York.

This article is for educational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment, and does not constitute medical or other professional advice. Always seek the advice of your qualified health provider with any questions you may have regarding a medical condition or treatment.

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