People with diabetes are at higher risk for certain cancers than those without the blood sugar disease, suggests a new study.
Based on data from a telephone survey of nearly 400,000 adults, researchers found 16 out of every 100 diabetic men and 17 out of every 100 diabetic women said they had cancer.
That compares to just seven per 100 men and 10 per 100 women without diabetes.
Cancer and diabetes
"The significant association between cancer and diabetes does not surprise us," said Dr Chaoyang Li, an epidemiologist at the Centres for Disease Control and Prevention in Atlanta, Georgia, whose findings appear in the journal Diabetes Care.
According to the CDC, nine % of US adults have diabetes.
After taking into account things like age, race, smoking and drinking habits, the researchers concluded that diabetic men and women were 10 % more likely to have had a cancer diagnosis of any kind.
Li said other studies have also found a link between the two diseases, although there is no proof that one causes the other.
The researchers found that the types of cancers that were more likely among diabetics differed between men and women.
Diabetic men and prostate cancer
Compared to people without diabetes, diabetic men were more likely to report having colon, pancreas, rectum, urinary bladder, kidney or prostate cancer (the latter only occurs in men). Diabetic women had more cases of breast cancer, leukaemia or cancer of the womb.
For men, the greatest increase in risk was for pancreatic cancer, with 16 per 10,000 cases among diabetics and just two per 10,000 among non-diabetics.
That corresponds to a four-fold difference after taking other factors into account.
Women's risk of leukaemia also varied greatly between the two groups. One per 1,000 women without diabetes said they had been diagnosed with the blood cancer, compared to three per 1,000 women with diabetes.
This new study is just a snapshot of people's medical history, and does not follow them over time.
Dr Fred Brancati, a professor at Johns Hopkins University in Baltimore, said he was struck by the findings, because some of the cancers kill people fast, meaning they wouldn't show up in the study.
"It shows there's a substantial pool of American adults who have diabetes and cancer," said Brancati, who was not involved in the study. "The authors rightly point out that these two conditions go together beyond chance alone, so it pays to think about them together."
Brancati's own research has shown that the risk of death from cancer among people with diabetes is about 40 % higher than among non-diabetics.
Li said it's still unclear why diabetes is tied to cancer. High blood sugar levels or excess blood insulin - a hormone that helps ferry sugar into the cells - might increase the risk, but that has not been proven.
Certain lifestyle choices reduce the risk of both diabetes and cancer, such as maintaining a healthy weight and not smoking.
Li said the findings are an important reminder for people with diabetes and their doctors to meet regular cancer screening guidelines and to discuss any possible cancer risk from anti-diabetic therapy. (Reuters Health/ May 2011)