New study results have strengthened the evidence that people who smoke cigarettes over a long period of time have an increased risk for developing colorectal cancer.
Researchers tested the association between long-term cigarette smoking and colorectal cancer after adjusting for multiple other factors that are generally associated with risk. From 1992 through 2005, the researchers followed almost 185,000 participants aged 50 to 74 years old.
Participants who smoked cigarettes for 40 or more years, or who did not quit before age 40, had a 30 percent to 50 percent increased risk of developing colon or rectal cancer, even in analyses that adjusted for 13 other potential risk factors.