Older overweight women have another compelling reason to shed excess pounds. A new study shows that older overweight women significantly increase their risk of acute leukemia.

Acute myelogenous leukemia (search) (AML) is the most common form of leukemia in adults and the rates of this cancer are growing among older adults. It is not an inherited disease but the result of genetic damage to developing cells in the bone marrow.

Epidemiologist Julie Ross, PhD, and colleagues at the University of Minnesota observed more than 37,000 women for a period of approximately 14 years. At the start of the study the women were free of cancer. However 200 of them developed leukemia during the observational period.

Women diagnosed with leukemia are more likely to be overweight or obese compared with those without the disease. These women also reported less physical and leisure time activity compared with women not diagnosed with leukemia.

Of the women diagnosed with leukemia, 74 women were specifically diagnosed with acute myelogenous leukemia. An increased risk of acute myelogenous leukemia was seen with increasing BMI, an indirect measure of body fat. This association was not seen for other types of leukemia.

"We found that the risk for getting AML was 90 percent higher in overweight women aged 55 and older who had a body mass index of 25-29 (overweight)," says Ross, one of the study’s researchers. In participants with a BMI of 30 or more (defined as obese), the risk of leukemia escalated to nearly 140 percent above those women who had reported normal weight.

Measures to reduce obesity may help prevent the incidence of adult AML, researchers say.

“The fact that survival rates for AML are extremely poor for older individuals makes identifying people who are at increased risk for this cancer of public health importance,” Ross notes. "Given that fact that 65 percent of adults in the U.S. are overweight or obese, the projection that we can make from our study is that about 30 percent of AML in older adult women could be due to being overweight or obese."

Obesity has long been linked to a number of malignancies, including colon and breast cancer, but few prospective studies have explored the potential link with leukemia. Scientists are not sure why a higher BMI increases the risk of AML in older adult women, but theorize that an impaired immune system, common in obese individuals, may play a role. Changes in metabolism associated with obesity, and hormonal changes seen in overweight and obese individuals, might also contribute to this risk.

The findings are published in the November issue of Cancer Epidemiology, Biomarkers & Prevention.

By Kelli Miller, reviewed by Brunilda Nazario, MD

SOURCES: American Cancer Society. News release, University of Minnesota. Cancer Epidemiology, Biomarkers & Prevention, November 2004; vol 13: pp 11.