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Joshua Hawkins of BGR.com has stated that 80 to 90 percent of lifelong smokers never develop lung cancer.

To quote the article:

Scientists may have discovered why lifelong smokers never get lung cancer. That sentence probably seems silly, especially given that cigarettes are the number one risk factor for lung cancer. Despite tobacco products being the cause of 90 percent of deaths, lifelong smokers somehow tend to avoid getting lung cancer. […]

However, based on the findings of this study, it could play a large part in why 80 to 90 percent of lifelong smokers never develop lung cancer.

There doesn't seem to be any source for the claim, although a study in Nature Genetics was linked in the article and that is behind a paywall.

As pointed out in the accepted answer to Skeptics.SE question, Does smoking cigarettes cause lung cancer?, smoking definitely causes cancer, but do 80 to 90 percent of lifelong smokers actually never develop lung cancer?

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  • Comments are not for extended discussion; this conversation has been moved to chat.
    – Oddthinking
    Jun 4 at 13:31

3 Answers 3

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This study from 2018 has a table (Fig.3) for lifetime risk of lung cancer, with that being ~12-14% for current smoker, and less than 2% for never-smoker.

So, it is true that 80-90 percent of smokers never develop lung cancer.

At the same time, smoking massively increases the risk of lung cancer.

Citation in case the link to the study goes bad:

Christina Bruder, Jean-Luc Bulliard, Simon Germann, Isabelle Konzelmann, Murielle Bochud, Magali Leyvraz, Arnaud Chiolero, Estimating lifetime and 10-year risk of lung cancer, Preventive Medicine Reports, Volume 11, 2018, Pages 125-130, ISSN 2211-3355, https://doi.org/10.1016/j.pmedr.2018.06.010. (https://www.sciencedirect.com/science/article/pii/S2211335518301062)

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  • 5
    That 2% lifetime incidence of lung cancer in non-smokers sounds too high. Typical estimates tend to say that the risk of lung cancer is 20-25 time higher for smokers than non-smokers.
    – matt_black
    Jun 1 at 13:06
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    the opposite of current smoker would include former smokers, that might explain the difference.
    – Christian
    Jun 1 at 13:21
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    @Christian No, former smoker is a separate category in that statistic that I just left out in my answer. I'd say the discrepancy is due to me eyeballing a bar chart. I didn't find the numbers relating to the chart that I based this answer on (it's figure 3). I think that is cited from somewhere.
    – kutschkem
    Jun 1 at 13:46
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    @matt_black I wonder what the risk is for never smoker who at the same time are exposed to second hand smoke...
    – Michael
    Jun 1 at 19:10
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    I suppose smokers also inhale more second hand smoke, either their own, of from being around other smokers more frequently
    – Christian
    Jun 2 at 8:18
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Note that the claim was specifically made about lung cancer. Smoking can cause many different types of cancer. Someone who dies from smoking-related throat, oral, stomach, etc. cancer wouldn't be included in those numbers, even if they would have developed lung cancer otherwise.

According to Cancer Council NSW, 1 in 8 cancer cases (all types) are caused by smoking, as are 1 in 5 cancer deaths. In Australia, 81% of all lung cancer cases are attributable to smoking. The CDC says that nearly 90% of lung cancer deaths are caused by smoking, and smoking increases your risk of lung cancer by 2500%. They also note that smoking can cause cancer "almost anywhere in your body". Smoking also makes it harder for your body to fight cancer and can lower your odds of surviving a non-smoking-related cancer.

So do 80%+ of smokers never develop (specifically) lung cancer? Perhaps, but that's a really limited and naïve way of looking at it. When nearly 1 in 5 deaths (all causes) in the US are caused by smoking and when smoking lowers your average lifespan by a decade, you've got a lot more to worry about than just lung cancer. The original article talks about smokers never developing lung cancer due to "DNA repair genes" that protect them. It doesn't mention, however, what percentage of those smokers actually have those genes. Based on all the statistics we have, it's more likely that they never developed lung cancer because smoking found some other way to kill them first.

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    "they never developed lung cancer because smoking found some other way to kill them first" Yes the issue of 'survivor bias' is is a really important point. My understanding is that smoking is also linked to heart disease which is a major killer. There are also other issues like emphysema which might not kill you very fast but make life much less pleasant.
    – JimmyJames
    Jun 1 at 16:16
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    There are also the "lifetime smokers" who die in auto accidents in their 20's. That doesn't mean those folks were somehow immune, just that something else got them first.
    – T.E.D.
    Jun 1 at 18:44
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    It's more than just cancer, heart disease is another big one. A heavy smokers (>20 per day) on average have a 13 year shorter lifespan, while light smokers have a reduced lifespan of 5 years. Being "lifelong" smoker doesn't really mean much, as with many other things we enjoy, it's about moderation.
    – rtaft
    Jun 1 at 18:50
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    @T.E.D.: Bonus, they're actually more likely to get in car accidents, use hard drugs, etc. than non-smokers (the same people who begin smoking young tend to engage in other high-risk behaviors too). So they're more likely to die young of non-smoking causes too, which means they never get a chance for cancer to develop. Jun 2 at 14:48
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    @JimmyJames And emphysema, which is even more common for smokers and typically shortens their life expectancy to about 5 years after diagnosis. Jun 3 at 11:19
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It is an oversimplification to assume that even the majority of lifelong smokers 'must' develop lung cancer and die from it. There are other causes of death, and lung cancer is a leading cause among older smokers.

The Nature article gives:

Epidemiological studies have estimated the risk of lung cancer with total lifetime smoking dose, duration, intensity and timing of cessation. It has been reported that 70% of smoking-related mortality occurs among those of advanced age, with 80–90% of life-long smokers never developing lung cancers.

— Zhenqiu Huang, Shixiang Sun et al.: "Single-cell analysis of somatic mutations in human bronchial epithelial cells in relation to aging and smoking", Nature Genetics volume 54, pages 492–498 (2022). doi

They reference these sources for this:

— Burns, D. M.: "Cigarette smoking among the elderly: disease consequences and the benefits of cessation", Am. J. Health Promot. 14, 357–361 (2000). doi

— Crispo, A. et al.: "The cumulative risk of lung cancer among current, ex- and never-smokers in European men", Br. J. Cancer 91, 1280–1286 (2004). doi

The Crispo et al. paper then has this informative graphic, that at the same time shows that the simple equation 'smoking=certain lung cancer' is an untruthful and massive oversimplification, as well that lifelong non-smokers certainly develop not as much cancer compared to smokers (very similar graphics/results for Italy, Germany, Sweden):

enter image description here

Effects of stopping smoking at various ages on the cumulative risk (%) of death from lung cancer up to age 75 at incidence rate for men in Europe.

Note that in this paper the cumulative risk was calculated as between the highest in Germany with 25.7 (24.3–27.0) and the lowest in Sweden with 12.6 (11.3–13.9), each for the highest category of smoking 25+ cigarettes a day. But Sweden also had a lower risk for non-smokers with 0.4 compared with Germany at 0.6.

The age-standardised mortality rate for lung cancer among Swedish males is substantially lower than in other European countries, at 22.6 per 100000 for the year 2000, while current mortality rates in the UK (48.6), Germany (46.2) and Italy (52.6) are more typical of other European countries (Ferlay et al, 2001). The difference between Sweden and the other countries cannot be explained by differences in consumption.

— Crispo

The Burns paper highlights:

The distribution of excess mortality with age is not uniform across the three major causes of excess smoking-induced mortality. Coronary heart disease mortality is by far the largest cause of smoking-induced ex- cess mortality under age 50. By age 55, lung cancer has increased to equal and then to exceed coronary heart disease as a cause of death.

Lung cancer is believed to result from a series of inheritable changes in cells exposed to carcinogens.

These changes may occur sequentially or simultaneously, but they occur relatively slowly, and a substantial change in cell morphology, structure, and replicative machinery is necessary prior to transformation of a cell into a cancer. This is a process where the future rate of cancer incidence is built on a foundation of prior extensive molecular and genetic change that grows steadily with duration of smoking exposure. In contrast to coronary artery disease, where a single lesion in an otherwise normal heart can cause infarction and death, the long lag time required to produce carcinogenic transformation in the smoker precludes high rates of cancer early in life.

— Burns

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