According to lead author Joseph C. Anderson, MD of Stony Brook University in New York, among 1,252 women who underwent screening for colorectal cancer, obesity was the strongest risk factor for developing the disease.
For the study, Anderson and colleagues examined the records of 1,252 women who underwent colonoscopy, classifying patients by age, smoking history, family history of colorectal cancer, and body mass index or BMI. Obesity was defined as having a BMI of 30 or higher.
For smoking, patients were divided into three groups: heavy exposure, low exposure, and no exposure. Patients who were in the heavy exposure group included women who had smoked more than 10 "pack years" and who were currently smoking or had quit in the past 10 years.
Then they looked to see who had the most polyps, and who was more likely to have them at all.
Results showed that although smoking posed a significant increased risk for colorectal neoplasia, obesity was the highest attributable risk factor for developing the disease.
BMI accounted for one-fifth of all significant polyps detected during colonoscopy. Of those patients who had colorectal neoplasia, 20 percent were obese and 14 percent were smokers.
"BMI was a huge risk factor. And it's a risk factor that's increasing," Anderson said. BMI was not linked to the risk of colon cancer for men, Anderson and colleagues found.
"We need to counsel people on things like losing weight and staying thin. Given the increasing number of obese patients in the United States, identifying them as high risk may have important screening implications," he said.