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Smoking ups colon cancer risk, more so for women


Smoking increases the risk for developing colon cancer, and female smokers appear to have a greater risk than male smokers, according to a Norwegian study.

“Globally, during the last 50 years, the number of new colon cancer cases per year has exploded for both men and women,” one of the study authors, Inger Torhild Gram, MD, PhD, a professor at the University of Tromsø in Norway, said in a news release. “Our study is the first that shows women who smoke less than men still get more colon cancer.”

As reported April 30 on the website of Cancer Epidemiology, Biomarkers and Prevention, a journal of the American Association for Cancer Research, Gram and her colleagues examined the association between cigarette smoking and colon cancer, by tumor location, in a Norwegian cohort of more than 600,000 men and women.

The participants had a short health exam and completed questionnaires about smoking habits, physical activity and other lifestyle factors. They were followed by linkage to the Cancer Registry of Norway and the Central Population Register. During an average 14 years of follow-up, close to 4,000 new colon cancer cases were diagnosed.

Gram and colleagues found that female smokers had a 19% increased risk compared with women who never had smoked, while male smokers had an 8% increased risk compared with never-smokers.

In addition, women who started smoking when they were 16 or younger and women who had smoked for 40 years or more had a substantially increased risk of about 50%. The dose-response association between the number of cigarettes smoked per day, number of years smoked and number of pack-years smoked and colon cancer risk was stronger for women than it was for men.

“The finding that women who smoke even a moderate number of cigarettes daily have an increased risk for colon cancer will account for a substantial number of new cases because colon cancer is such a common disease,” Gram said.

The International Agency for Research on Cancer, a branch of the World Health Organization, recently has established a causal relationship between smoking and colorectal cancer, Gram noted, “but unfortunately, this is not yet common knowledge, neither among health personnel nor the public.”

Read the study abstract:


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