Why do some people smoke a pack of cigarettes a day and live to be 90 without getting lung cancer?

November 17 is International Lung Cancer Day. Smoking is recognized as the most important risk factor for lung cancer. Tobacco produces a variety of carcinogenic chemicals during combustion, such as polycyclic aromatic hydrocarbons, aromatics and their amines, nitrosamines, etc. Tobacco itself contains inorganic carcinogens such as arsenic, nickel, and chromium.

In addition to increasing the risk of lung cancer, smoking also increases the risk of bladder cancer, esophageal cancer, oral cancer, breast cancer and many other cancers.

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But many people still can't figure out why many smokers don't get lung cancer? Some people even smoke a pack of cigarettes a day and live to 90 years old without getting lung cancer? But some people who never smoke still get lung cancer? What's going on?

Individual differences and genetic factors

Smoking does not necessarily lead to lung cancer. Non-smokers may get lung cancer. This is an undeniable fact.

It is precisely because of this that some people always say that it doesn’t matter whether you quit smoking or not. Smoking does not necessarily lead to lung cancer, and you can get lung cancer even if you don’t smoke.

On the surface, it sounds reasonable, but in fact, it is untenable from the perspective of medical science or basic logic. Smokers do not get lung cancer and even live longer. Analyzing the reasons, innate genes are a big factor.

Some people are born with good genes. There are always a few people who are "different" and carry specific genes that give them natural resilience. It's like there are always a few people who are really "geniuses" in some aspects, and under the same conditions, there is no way to compare with them, but obviously such people are not universal, and we can't draw universal conclusions based on this.

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According to a study in the United States, the reason why people who smoke live long may be because they have some kind of innate resilience. These people are biologically different and have some kind of innate genetic mutation that enhances cell maintenance and repair, making their response to smoking different from that of most other people.

That is to say, smoking does "harm" these people, but because they have strong innate repair abilities, the actual damage they suffer may be small. If they don't smoke, they may live longer and have fewer and better lives. Obviously, most people do not carry this gene mutation and do not have this innate recovery ability. Most of us do not have the qualifications to be willful, otherwise we would be "seeking death."

Cancer is not caused by a single factor

In terms of carcinogenesis itself, the occurrence of most cancers is not caused by a single factor, but is the result of the combined action of multiple factors.

Smoking is an important carcinogenic factor for lung cancer, but it is not the only factor. In other words, in addition to smoking, there are other risk factors. For example, family history (genetic factors), long-term living in air-polluted areas, long-term exposure of women to kitchen fumes, and long-term contact or exposure to certain harmful substances or harmful environments in certain occupations, such as contact with asbestos, coal smoke tar, arsenic, etc. The risk of lung cancer in such occupations is relatively high.

Smokers may do very well in other aspects except smoking. Lung cancer is the result of multiple factors. Just as grades are determined by multiple factors, we cannot simply draw conclusions about grades by focusing on a single factor.

Survivorship bias

In addition, we must also consider the factor of "survivor bias" and not generalize. People who smoke live to 90 years old, this kind of thing is easy to attract everyone's attention. When the information you get only comes from these few survivors, the results you see are actually screened invisibly. Generalizing from a few cases, using the individual to represent the whole, the conclusion drawn from this is obviously not objective.

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Many things in the world are probabilistic. People who smoke have a higher risk of getting lung cancer, but they are not certain to get lung cancer. This is just like people who study hard may not always get good grades, and those who don't seem to work hard may not always get bad grades.

But from a probability perspective, under the same conditions, people who work hard are more likely to achieve good results than those who don't. The harder you work, the luckier you are. Our choices are based on high probabilities and cannot be absolute. Smokers have a greater risk of cancer than non-smokers. The higher the smoking index, the greater the probability of cancer.

Summarize

To understand the complex relationship between smoking and lung cancer, we need to go beyond simple causal logic and recognize that health is the result of the combined effect of multiple factors.

While some smokers may live longer, it does not mean that smoking is harmless. Everyone's genes, lifestyle and environment are different, and these factors together determine individual health outcomes.

We cannot ignore the universal risks of smoking because of individual cases. In order to maximize the possibility of health, the best choice is not to smoke. Especially for non-smokers, stay away from tobacco and secondhand smoke, and for smokers, quitting smoking as soon as possible is the most responsible way for themselves and their families.

Planning and production

Author: Pan Zhanhe, Chief Physician, Master's Supervisor, Department of Oncology, Zhongshan Hospital, Xiamen University

Reviewer: Tang Qin, Director and Researcher of the Science Popularization Department of the Chinese Medical Association

Planning丨Fu Sijia

Editor: Fu Sijia

Proofread by Xu Lailinlin

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