Blood Sugar Levels Linked to Cancer Rates

In large Korean study, higher levels meant higher incidence of disease

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HealthDay Reporter

TUESDAY, Jan. 11, 2005 (HealthDayNews) -- If Americans don't do something about their growing waistlines, cancer may soon join diabetes and heart disease as illnesses on the rise because of this country's obesity epidemic.

A study in the Jan. 12 issue of the Journal of the American Medical Association found that higher fasting blood glucose levels were associated with an increase in cancer incidence and cancer deaths.

"In the long run, the implication is that as the world becomes heavier and blood sugar rises, that could contribute to an increasing burden of cancer," said study co-author Dr. Jonathan Samet, chairman of epidemiology at the Johns Hopkins Bloomberg School of Public Health.

Fasting blood glucose levels are used to measure the amount of sugar in your blood after you haven't had anything to eat or drink for at least eight hours. A reading under 110 mg/dl is considered normal, 110-125 mg/dl is impaired, and a fasting blood glucose level over 126 mg/dl indicates diabetes.

More than 150 million people worldwide currently have diabetes, according to the study, and that number may double by 2025. Excess weight is a major risk factor for diabetes. In fact, according to the American Diabetes Association, nine out of 10 people newly diagnosed with type 2 diabetes are overweight.

The current study looked at 10 years of data from nearly 1.3 million Korean men and women. People in Korea tend to be thinner and have a lower incidence of diabetes than people in the United States, according to the study and an accompanying editorial.

There were 829,770 men and 468,615 women included in the research. All were between the ages of 30 and 95. The data came from the Korean Cancer Prevention Study, with information provided by the National Health Insurance Corp. During a biennial physical, each person was surveyed about their lifestyle habits, such as smoking and alcohol consumption. They also had their blood sugar levels measured.

The researchers controlled the data to account for smoking and alcohol use.

During the study period, almost 26,000 people died from cancer. Death rates were highest for those with higher levels of fasting glucose. Overall, those with fasting glucose levels above 140 mg/dl had a 29 percent higher risk of dying from cancer. For pancreatic cancer, the risk of dying was doubled for those with the highest fasting glucose levels. Only 848 of the cancer deaths occurred in people with fasting glucose levels of less than 90 mg/dl.

More than 56,000 people were diagnosed with cancer during the study. Cancer incidence rates also went up as glucose levels rose. Overall, the risk of developing cancer was 13 percent higher for someone with a fasting glucose level between 110 mg/dl and 125 mg/dl, compared to those who had readings under 90 mg/dl. For someone with fasting glucose above 140 mg/dl, the risk rose to 22 percent higher than someone under 90 mg/dl.

Once blood sugar levels rose over 110 mg/dl, cancer incidence rose for leukemia and cancers of the esophagus, larynx, stomach, colon, rectum, liver, bile duct, pancreas, lung, prostate, kidney, bladder and brain, the study found.

In the past, both obesity and diabetes have been linked to the development of cancer, but it was difficult to know which factor was truly responsible because most people with diabetes are also overweight.

"It's been difficult to disentangle whether it's diabetes or obesity [that's contributing to cancer]," said American Cancer Society epidemiologist Dr. Carmen Rodriguez, who added that's exactly why the new study is so useful, since it was done on a thinner population.

"The size of this study is impressive," said Rodriguez, "and it probably contains a lesson for the American people: Maintaining a healthy weight and a healthy lifestyle are important."

Samet echoed that sentiment: "There are many reasons to be concerned about the rising waistline of the U.S. population, and here is another untoward consequence of being overweight."

In the accompanying editorial, epidemiologists from the University of Michigan Medical School wrote, "Since the prevalence of diabetes is higher in the United States than in Korea, it is possible that preventing diabetes may have a more important effect in the United States." They added that preventing obesity and diabetes "may ultimately diminish the burden of cancer for future generations."

More information

To learn more about preventing diabetes and high glucose levels, visit the American Diabetes Association.

SOURCES: Jonathan Samet, M.D., M.S., professor and chairman, epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore; Carmen Rodriguez, M.D., M.P.H., epidemiologist, American Cancer Society, Atlanta; Jan. 12, 2005, Journal of the American Medical Association

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