A recent study asked a large group of individuals in Norway about their smoking habits and checked the records of each person against the Norwegian cancer registry.
The results of the study showed that both men and women had an increased risk for colon cancer if they had been smokers. The risk for colon cancer in women smokers was higher than in men.
"Ask your doctor for help quitting smoking."
Ranjan Parajuli, PhD student, and Inger T. Gram, MD, PhD, from the Department of Community Medicine at the University of Tromsø in Norway, led an investigation into the gender differences in smoking risks for developing colon cancer.
In Norway, from 1972 to 2003, a total of 602,242 people were enrolled into a national population registry when they were between the ages of 19 and 67. In 2007, the researchers followed up with the participants.
Each of the participants in the study filled out survey information about his or her smoking habits. Questions in the survey asked the following:
- How old were you when you started smoking?
- How many cigarettes per day do/did you smoke?
- How many years have/had you smoked?
Pack-years were calculated for each smoker by multiplying the number of packs a person smoked per day by the number of years that person has smoked. For example, if a person smoked one pack per day for 20 years, they had 20 pack-years. Or, if a person smoked two packs per day for 10 years, they still had 20 pack-years.
The national registry was linked to the Cancer Registry of Norway.
The results of the study found that during the 14-year follow-up period, 3,998 people were diagnosed with colon cancer. Of the 3,998 people, 54 percent were men and 46 percent were women.
The researchers found that women who had been smokers had a 19 percent higher risk for colon cancer compared to women who had never smoked.
Men who had been smokers had an 8 percent higher risk for colon cancer compared to men who had never smoked.
Women who had started smoking before 16 years of age had a 48 percent higher risk for developing colon cancer compared to women who had never smoked.
Women who smoked 20 cigarettes or more per day had a 28 percent higher risk for developing colon cancer than women who were never smokers.
Women who had smoked for 40 years had a 47 percent increased risk for colon cancer compared to women who never smoked. Men who had smoked for 40 years had a 30 percent increased risk for colon cancer compared to men who had never smoked.
Women with a smoking history of 20 or more pack years had a 33 percent higher risk for colon cancer compared to women who had never smoked.
Overall, the researchers said that the women in these high-risk, heavy smoker categories had “a significantly increased risk (for colon cancer) of more than 20 percent compared with never smokers.”
The colon is shaped a bit like a square. The right side, where waste enters the colon, and the topside, where waste moves across the colon, is called the proximal area of the colon. Female smokers had a 40 percent greater likelihood to have colon cancer in the proximal area of the colon compared to women who had never smoked.
The study authors concluded that smoking increases the risk for developing colon cancer in both men and women, but that women who smoked had an even higher risk for developing colon cancer compared to men.
This study was published in April in Cancer Epidemiology, Biomarkers & Prevention.
The Norwegian Cancer Society provided funding for this project. No conflicts of interest were declared.