Overweight and obesity in adolescence were associated with an increased risk for colon cancer later in life among both men and women, according to the results of a recent study. Obesity, but not overweight, was also linked to subsequent rectal cancer.
Researchers were extending previous work looking at the association between body mass index (BMI) measured at adolescence and risk for colorectal cancer (CRC) among men. The study was expanded to include women and by updating the cancer registry linkage data to increase the number of CRC cases. The results were published in Cancer.
“The association between adolescent BMI and CRC among men has been addressed in several studies, some reporting little or no association, a possible association, or a positive association,” wrote Zohar Levi, MD, of the Rabin Medical Center, Tikva, Israel, and colleagues.
The study included 2,967 cases of CRC diagnosed in a Jewish population, including 1,977 cases diagnosed in men and 990 diagnosed in women. Participants had undergone health examinations at ages 16 to 19 between 1967 and 2002 and were followed in the cancer registry.
Patients were followed for a median of 23.3 years, and the median age at follow-up was 40.6. Overweight and obesity as measured by BMI increased the risk for colon cancer in men (overweight hazard ratio [HR], 1.53; obesity HR, 1.54) and in women (overweight HR, 1.54; obesity HR, 1.51). For rectal cancer, obesity, but not overweight, was associated with increased risk for rectal cancer in men (HR, 1.71) and women (HR, 2.03).
“Several explanations have been suggested for the association of higher BMI with CRC,” the researchers wrote. “These include downregulation of adiponectin; upregulation of leptin, interleukin-6, and tumor necrosis factor alpha; increased insulin and insulin-like growth factor 1; the impact of nonalcoholic steatohepatitis; low-grade inflammation; and an altered immune response.”
The researchers categorized CDC BMI into seven groups and found that among men, compared with a low CDC healthy-range weight, obesity, overweight, and even a high CDC healthy-range weight had evidence of an increased risk for colon cancer (obesity HR, 1.63; overweight HR, 1.62; high healthy-range weight HR, 1.29).
“Our study is consistent with a graded increased risk of CRC with BMI category and is the first to show a significantly increased risk for colon cancer among those with a high CDC healthy-range weight in adolescence,” the authors wrote.
According to the researchers, few previous studies have reported on colon and rectal cancers separately.
“Our data indicate that the risk for rectal cancer may be increased only for obese adolescents, and this suggests possibly different mechanisms for colon cancer and rectal cancer,” the researchers wrote. “This might be supported by reports of a differential impact of obesity on the risk of adenomas and may provide some explanation for the inconsistencies concerning the association of BMI with rectal cancer in women reported in several studies.”