Smoking causes many types of illnesses — including some that people may not immediately associate with cigarettes, such as colon cancer. Smokers not only have a higher risk of developing colon cancer, they also have a higher risk of dying from the disease.

Colon Cancer: The Smoking Connection

“Cigarette smoke contains many carcinogens [cancer-causing agents], benzopyrenes being the most well-known,” says Thomas Imperiale, MD, professor of medicine and associate director for research for the Division of Gastroenterology at the Indiana University School of Medicine. “It’s believed that these carcinogens cause damage to the DNA and, over time, the body’s ability to repair that damage decreases.”

Colon Cancer: Does Quitting Reduce Risk?

Breaking your smoking habit is always a good idea in terms of cancer prevention. But, while quitting can help reduce your risk of developing colon cancer, there is a long lag time before the risk drops, says Dr. Imperiale. “There’s an ‘induction’ period, too,” he explains. “What’s been strongly linked with [colon] cancer is smoking in your teens and 20s, because there’s about a 30-year lag between the onset of smoking and the onset of adenocarcinomas" — pre- or early cancer. So, just as it takes a long period for the cancer to show up, it can take an equally long time for the body to return to the average level of risk.

Colon Cancer: Screening for Smokers

At present, there’s no set guideline for when smokers should be screened for colon cancer if they have no other apparent risk factors. The American Cancer Society (ACS) guidelines suggest that seemingly healthy people who are at low risk for developing colon cancer should be screened starting around age 50; how often after that you would have your next colonoscopy screening depends on results of that first test.

Imperiale says that the evidence is strong enough to indicate that the risk of colon cancer from smoking is as high as having a first-degree relative — parent, sibling, or child — with colon cancer. The ACS recommends that those people begin screening at age 40, but does not recommend the same for smokers or former smokers. Unfortunately, “for some reason, we’ve been skirting the issue of screening these people more aggressively,” he says.

As more research is done on the link between smoking and colon cancer, smoking may become recognized as a risk factor that should prompt earlier screening. Until that happens, if you are or were a smoker, talk to your doctor about whether you are a candidate for earlier testing.

Keep in mind that it’s never too late to quit smoking. According to Imperiale, “If a smoker does quit the habit, although it takes time for the body to return to its ability to repair damaged DNA, it does happen over time."