In a broad review of scientific literature, the US’s top doctor has concluded that cigarette smoking — long known to cause lung cancer and heart disease — also causes diabetes, colorectal and liver cancers, erectile dysfunction and ectopic pregnancy.
In a report, the acting surgeon general, Dr Boris D Lushniak, significantly expanded the list of illnesses that cigarette smoking has been scientifically proved to cause.
The other health problems the report names are vision loss, tuberculosis, rheumatoid arthritis, impaired immune function and cleft palates in children of women who smoke.
Smoking has been known to be associated with these illnesses, but the report was the first time the federal government concluded that smoking causes them.
The finding does not mean that smoking causes all cases of the health problems and diseases listed in the report, but that some of the cases would not have happened without smoking. The surgeon general has added to the list of smoking-related diseases before. Bladder cancer was added in 1990 and cervical cancer in 2004.
The report is not legally binding, but is broadly held as a standard for scientific evidence among researchers and policy makers.
“I thought the science was very well done and up to date,” said Dr Robert Wallace, a professor of epidemiology and internal medicine at the University of Iowa, who helped review the report.
The report comes 50 years after the pivotal 1964 surgeon general’s report in which the government concluded for the first time that smoking caused lung cancer. That report was credited with starting to change public attitudes toward smoking, which has declined sharply. In 1965, about 43 per cent of adults were smokers; in 2012, about 18 per cent were.
But that decline has slowed in recent years, and the new report calls for stronger action in combating smoking. The report concluded that the evidence was insufficient to say that smoking caused prostate cancer. The evidence was suggestive, but not definite, that smoking causes breast cancer.
While smoking causes most cases of lung cancer, it causes only a small fraction of liver and colorectal cancers. A current smoker is 25 times as likely to develop lung cancer as someone who has never smoked, but only about 1.5 times as likely to develop liver cancer.
“It is a fairly modest association, but because so many people smoke, it’s still an important cause of these cancers,” said Neal Freedman, an epidemiologist at the National Cancer Institute.
He pointed out that the surgeon general last looked at the effect of smoking on liver cancer in 2004, and found the evidence only suggestive. Since then, 90 new studies have been published allowing the surgeon general to conclude smoking is a cause.
The report also finds that the risks of lung cancer are far higher today than in past decades, even though smokers today consume fewer cigarettes. In 1959, women who smoked were 2.7 times as likely as women who never smoked to develop lung cancer, and by 2010, the additional risk had jumped nearly tenfold. For men, the risk doubled over the same period. The report said changes in cigarettes’ design, namely to the filter, contributed to the increased deadliness.