Study links diabetes and colorectal cancer

06/04/04

Researchers attribute increased risk to elevated glycated hemoglobin concentrations, finding a continuous, predictive relationship independent of other risk factors

Diabetics are three times more likely to develop colorectal cancer than people with normal blood sugar levels, according to a team of scientists at the University of Cambridge, U.K., reporting in this month's edition of the journal Cancer Epidemiology, Biomarkers and Prevention.

The researchers found a continuous relationship between glycated hemoglobin (HbA1c) concentrations and colorectal cancer risk, even in individuals not known to have diabetes.

"When both glycated hemoglobin levels and diabetes status were included as variables in the same model, glycated hemoglobin remained a significant predictor of colorectal cancer risk, while the effect of diabetes was not significant," said Kay-Tee Khaw, M.D., FRCP, professor in the clinical gerontology unit of the university's School of Clinical Medicine, and principal investigator for the study. "The significantly increased risk of diabetes with colorectal cancer appeared to be mediated largely through the level of glycated hemoglobin."

Khaw noted further that glycated HbA1c could predict colorectal cancer independently of diabetes and such other risk factors as obesity and cigarette smoking – and do so at concentrations below those commonly accepted as the standard for a diagnosis of diabetes.

For every one percent increase in glycated hemoglobin there was a corresponding 33 percent increase in risk across the population.

The results are based on data derived from the European Investigation into Cancer–Norfolk Study, a prospective population study of the connection between diet and cancer. Participants, more than 30,000 men and women, ages 45 to 79, who live in Norfolk, U.K., completed health and lifestyle questionnaires and received medical examinations. Non-fasting blood samples were drawn. Khaw and her colleagues measured glycated hemoglobin levels in the blood of the nearly 10,000 people for whom the information was available, and who did not report having cancer at the time of the survey. The lowest concentrations of HbA1c averaged about 5.2 percent. Individuals with blood glycated hemoglobin levels there and below had the lowest risk of developing colorectal cancer.

"Our work augments the increasing evidence of a link between abnormal glucose metabolism and increased colorectal cancer risk," Khaw said. "Earlier research posited a relationship between insulin resistance, glucose and colon cancer, on the basis of the fact that insulin promotes the growth of colon cells and colon tumors. Both diabetes and colorectal cancer may share common predisposing factors. For example, a high-fiber diet and regular exercise may protect against both diseases."

Previous research was prompted by scientific interest in the relationship between two, seemingly disparate conditions. Researchers had noted the prevalence of overweight and obesity in the U.S. and much of the Western world – leading contributors to the development of type-2 diabetes – was commensurate with the high incidence of colon cancer in these parts of the world.

Source: Eurekalert & others

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