Korean Study Suggests Diabetes-Cancer Link
January 12, 2005

A study of more than 1 million South Koreans suggests diabetes can raise the risk of developing and dying from several types of cancer, including digestive-tract tumors.

This is not the first study to suggest such a link, but it sheds more light on exactly how diabetes might contribute to cancer.

Diabetes is often linked to obesity, and obesity is known to increase the risk of cancer. Yet few of the study participants were overweight, so the researchers think high blood sugar levels - another hallmark of diabetes - might also be involved.

The highest risks for developing cancer and dying from it were found in people with the highest blood sugar levels, the South Korean researchers found.

The study appears in Wednesday's Journal of the American Medical Association.

Researchers analyzed data on 1.29 million South Korean men and women ages 30 to 95 who received health insurance from a group that covers government employees, teachers and their families. Participants were followed for up to 10 years starting in 1992.

About 5 percent of the participants had diabetes. A total of 26,473 participants died of cancer during the follow-up.

Participants with diabetes were roughly 30 percent more likely than those without to develop and die from cancer. The highest risks were for cancer of the pancreas, the organ that produces blood sugar-regulating insulin. Diabetes involves inadequate production or use of insulin.

Increased risks also were seen for cancers of the liver, esophagus and colon.

It is unclear how diabetes might lead to cancer, but lead author Sun Ha Jee, a public health researcher at Yonsei University in Seoul, said insulin may influence cell growth. Cancer is characterized by runaway cell growth.

A JAMA editorial said the data suggest in South Korea that an estimated 3.9 percent of cancer deaths in men and 0.8 percent of cancer deaths in women are attributable to diabetes - a modest portion partly attributable to the low prevalence of diabetes in South Korea.

It is unclear whether the findings would apply elsewhere. But since U.S. diabetes rates are high, with more than 18 million people affected, preventing the disease might have a greater effect on cancer rates and deaths in the United States, according to the editorial by Drs. Kathleen Cooney and Stephen Gruber at the University of Michigan.

Exercise and diet can help prevent the most common form of diabetes. The disease is strongly associated with obesity and older age but is being diagnosed in an increasing number of children and teenagers.