Study Suggests Breast Cancer Survivors Have Slightly Higher Risk of Diabetes

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A large Canadian study found that postmenopausal women who’ve been diagnosed with breast cancer have a slightly higher risk of diabetes compared to similar women who haven’t been diagnosed with breast cancer.

The research was published online in December 2012 by Diabetologia. Read “Incidence of diabetes among postmenopausal breast cancer survivors.”

Health care in Canada is delivered through a national health system. This system makes it a little easier to track health outcomes and do research on links between health factors and disease risk.

From a database of patients in Ontario, the researchers identified nearly 25,000 postmenopausal women who had been treated for early-stage breast cancer from 1996 to 2008. The women were all age 55 or older. They also identified nearly 125,000 similar women who hadn’t been diagnosed with breast cancer. The researchers then compared how many women in each group were diagnosed with diabetes from 1996 to 2008.

The researchers found that diabetes risk started to go up a little in women who’d been diagnosed with breast cancer about 2 years after diagnosis and became statistically significant 10 years after diagnosis. This means that the increase in diabetes risk was real and not just due to chance.

Women who had received chemotherapy after breast cancer surgery had a different diabetes risk profile. For them, diabetes risk was highest in the first 2 years after diagnosis and then went down.

Earlier research has suggested a link between diabetes and cancer. Studies have found that women diagnosed with diabetes have a higher risk of breast cancer compared to women never diagnosed with diabetes. Doctors aren’t sure exactly what is linking diabetes and cancer. Higher insulin levels may be part of the reason. The hormone insulin helps our bodies regulate blood sugar. Insulin also helps cells grow. Many people who have diabetes tend to have higher-than-normal insulin levels (hyperinsulinemia). This is partially because their bodies no longer respond to normal insulin levels.

While this study adds more evidence to the link between cancer and diabetes, it’s not clear from the results if the slight increase in diabetes risk is because of the breast cancer, the chemotherapy treatment, or other factors that are risks for both cancer and diabetes, such as obesity and a lack of exercise. More research is needed to understand the link between cancer and diabetes and to figure out whether it might influence prevention strategies and treatment for both diseases.

While your genetics play a role in developing both diabetes and breast cancer, there are steps you can take to ensure that your risk of both diseases is as low as possible. One of the best ways to avoid diabetes AND help keep your breast cancer risk as low as it can be is to have a healthy diet and lifestyle:

  • eat a diet low in added sugar and other sweeteners and rich in fruits and vegetables
  • maintain a healthy weight
  • exercise regularly at a moderate intensity
  • avoid alcohol
  • don't smoke

Visit the Breastcancer.org Lower Your Risk section to learn more about breast cancer risk and other steps you can take to keep yours as low as it can be.

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