Incidence rates for diabetes and cancer are increasing globally. Previous epidemiologic studies have observed increased risk between diabetes and several cancers, including breast, colorectal, liver, and pancreatic. Yet, the association between diabetes and other cancers remains unclear. Thus, researchers from the USA National Health Institute (NIH) evaluated the association between diabetes and cancer incidence and mortality in the prospective study.
According to Gabriel Lai, PhD, a cancer prevention fellow at the USA National Cancer Institute, study results provide further evidence that abnormal insulin and glucose signalling may contribute to cancer initiation and development. There are myriad benefits from avoiding diabetes through exercise, diet and maintaining a healthy body weight.
Lai and colleagues conducted a study using data from more than 500,000 predominantly white, non-Hispanic men and women aged 50 to 71 years. From 1995 to 1996, the participants completed questionnaires about age, education, body mass index, smoking status, self-reported health status, whether or not they had diabetes, physical activity, vitamin supplement use, intake of alcohol, fruits, vegetables and meat, family history of cancer, and among women, menopausal hormonal therapy. Researchers followed the patients for 11 years.
Results showed that diabetes was associated with an 8% increased risk for cancer among women and a 4% decreased risk for men. In previous research, a decreased risk for prostate cancer was associated with diabetes, which researchers believe might be due to the lower testosterone levels associated with diabetes. After excluding prostate cancer from their evaluation, Lai and colleagues found that diabetes was associated with a 9% increased risk for cancer in men. As for mortality, diabetes was associated with an 11% increased risk in women and a 17% increased risk in men. These risks appeared independent from other cancer risk factors, such as obesity and cigarette smoking.
After evaluating by cancer site, the researchers found diabetes was associated with a significant increase in risk for colon, rectal and liver cancers among men and women. In men, diabetes was associated with an increased risk for pancreatic and kidney cancers; in women, it was associated with an increased risk for stomach, anal and endometrial cancers. No association was found between diabetes and lung, skin or other cancers.
According to the authors, these results suggest that preventing or controlling diabetes may contribute to decreased cancer incidence and mortality. Follow-up studies to identify the biologic mechanisms involved are needed.