Doll and Hill report the link between smoking and lung cancer

Historical milestone — this page describes an event dated 1950. It is not current breaking news.

The number that started it

Richard Doll and Austin Bradford Hill opened their 1950 paper with a count, not a theory.

In England and Wales, deaths recorded as cancer of the lung rose from 612 in 1922 to 9,287 in 1947. That is roughly fifteenfold in a quarter of a century, far beyond what population growth could explain.

Some argued the rise was an illusion of better diagnosis. Doll and Hill judged that improved diagnosis could not be the whole story. Their conclusion was that it was right and proper to look for another cause.

How they looked

Twenty London hospitals agreed to notify every patient admitted with cancer of the lung, stomach, colon or rectum.

Almoners then interviewed those patients about their smoking, their exposure to car and fuel fumes, and their work. Each was matched with a hospital patient of the same age and sex who did not have cancer.

The final set was 1,732 patients thought to have one of those cancers, plus 743 controls. Of the cancer patients, 709 had carcinoma of the lung.

They also checked their own method. Fifty control patients were interviewed a second time, six months or more after the first, to see whether people described their smoking the same way twice.

What they found

Far more of the lung cancer patients smoked, and the risk climbed with the amount.

Their estimate was that above the age of 45, the risk rose in proportion to how much a person smoked, and that it might be roughly 50 times as great among people smoking 25 or more cigarettes a day as among non-smokers. They called this figure admittedly speculative, and they were right to.

One line in the paper does the most work. "We therefore conclude that smoking is a factor, and an important factor, in the production of carcinoma of the lung."

There is a second detail, easy to miss. Among non-smokers, the expected sex split would have been about 1 man to 15 women. The observed split was 0 to 16. That fits the idea that lung cancer risk is the same in men and women once smoking is set aside.

What this study cannot tell you

• This was a case-control study. It compared people who already had the disease with people who did not. That design shows a strong association. It cannot, on its own, prove cause.
• The smoking histories came from what patients remembered and were willing to say. The authors knew that and tested it, but memory is still memory.
• The 50-fold figure rested on estimating how many Londoners smoked each amount, from the control group. The authors flagged it as tentative rather than measured.
• It took Doll and Hill's later study following British doctors forward in time, and much other work, before the causal case was settled. The U.S. Surgeon General's report came 14 years later, in 1964.
• This is a summary of a historical study, not advice about your own care.

What is settled now

NCI states that tobacco smoke contains more than 7,000 chemicals, of which at least 250 are known to be harmful. Hydrogen cyanide, carbon monoxide and ammonia are among them.

NCI also puts numbers on stopping. People who quit smoking between the ages of 25 and 34 live about 10 years longer than those who keep going. Quitting between 35 and 44 adds about 9 years, between 45 and 54 about 6, and between 55 and 64 about 4.

People who quit before age 40 reduce their chance of dying early from a smoking-related disease by about 90 percent. Even people who quit in their 60s had a lower risk of death during follow-up than those who continued. Our page on quitting smoking covers what helps, and our page on smoking, vaping and lung cancer risk covers the newer products.

When to get checked

NCI notes that lung cancer sometimes causes no symptoms at all and is found on a chest x-ray done for something else. When symptoms do appear, check with a doctor for:

• Chest discomfort or pain.
• A cough that does not go away or gets worse.
• Trouble breathing, or wheezing.
• Blood in sputum, the mucus coughed up from the lungs.
• Hoarseness, or trouble swallowing.
• Loss of appetite, or weight loss for no known reason.
• Fatigue.
• Swelling in the face, or in the veins of the neck.

That last one is not vague. Swelling of the face and neck veins can mean a tumor is pressing on the large vein returning blood to the heart, and it needs urgent assessment.

For people without symptoms, the U.S. Preventive Services Task Force recommends a yearly low-dose CT scan for adults aged 50 to 80 with a 20 pack-year smoking history who smoke now or quit within the past 15 years. Our guide to lung cancer screening explains what that involves.

The group picture

SEER figures describe the United States population, not any one person.

Five-year relative survival for lung and bronchus cancer is 29.5 percent for cases from 2016 to 2022. By stage it is 65.5 percent while confined to the lung, 38.2 percent at nearby lymph nodes, and 10.5 percent once it has spread further.

Only 24 percent are found at that first stage. Fifty-one percent are already distant. An estimated 229,410 new cases and 124,990 deaths are projected for 2026, and lung cancer causes 20.0 percent of all cancer deaths in the country, more than any other type. Our page on lung cancer covers the differences between the types.

Seventy-five years after Doll and Hill counted death certificates, that is what the count looks like.

Sources

• Richard Doll and A. Bradford Hill, Smoking and Carcinoma of the Lung: Preliminary Report, British Medical Journal, September 30, 1950 — https://csts.ua.edu/files/2019/01/1950-09-30-BMJ-Smoking-Carcinoma-of-the-Lung-Doll-Hill.pdf
• NCI, Harms of Cigarette Smoking and Health Benefits of Quitting — https://www.cancer.gov/about-cancer/causes-prevention/risk/tobacco/cessation-fact-sheet
• NCI PDQ, Non-Small Cell Lung Cancer Treatment (Patient Version) — https://www.cancer.gov/types/lung/patient/non-small-cell-lung-treatment-pdq
• NCI PDQ, Cardiopulmonary Syndromes (Health Professional Version) — https://www.cancer.gov/about-cancer/treatment/side-effects/cardiopulmonary-hp-pdq
• SEER Cancer Stat Facts, Lung and Bronchus Cancer — https://seer.cancer.gov/statfacts/html/lungb.html
• USPSTF, Lung Cancer: Screening — https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/lung-cancer-screening

How this article was prepared

An AI-assisted editorial system helped prepare this page. No named medical reviewer has reviewed it unless one is listed.

The National Cancer Information Foundation publishes Cancer Explained. This page is for learning. It is not medical advice and does not suggest a test or treatment.

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