TUESDAY, June 29 (HealthDay News) -- Scientists report that smoking may boost the risk of colon cancer in older women by causing certain genetic mutations.

The study appears online June 29 in the Journal of the National Cancer Institute..

Previous research has indicated that current and former smokers are 18 percent more likely to develop colorectal cancer than those who never smoked, according to a news release from the journal's publisher. It's not clear, however, how smoking and tumors are connected, especially at the molecular level.

In the new study, the Mayo Clinic's Dr. Paul J. Limburg and colleagues examined statistics from the Iowa Women's Health Study, focusing specifically on almost 42,000 women aged 55 to 69 who responded to a questionnaire.

The researchers didn't discover much of connection between smoking and a higher risk of colorectal cancer overall. But they did find a strong link between smoking and a specific type of colorectal cancer that's connected to genetic mutations and variations.

The researchers caution that older women are especially susceptible to this subtype of colorectal cancer, so the link with smoking may not hold true for all people.

Even so, the researchers wrote in the news release that new colorectal screening tests, such as those that look for genetic changes, could offer especially useful information to longtime smokers.

More information

For more about colorectal cancer, try the U.S. National Library of Medicine.