Now, a review analyzing the data collected by 47 studies from across the globe — including the United States, United Kingdom, China, Australia, and Japan, to name but a few — confirms, beyond doubt, that diabetes heightens the risk for cancer.
The study authors note that women with diabetes are especially affected. They appear to be more exposed than men to the development of malign tumors.
The findings of this global review — which assessed the health-related data of almost 20 million people — are discussed in a paper now published in the journal Diabetologia.
Women at higher risk than men
The review was conducted by researchers led by Dr. Toshiaki Ohkuma, from the George Institute for Global Health at the University of New South Wales in Sydney, Australia.
His colleagues hailed from the University of Oxford in the U.K., and Johns Hopkins University in Baltimore, MD.
Dr. Ohkuma and his colleagues discovered not only that diabetes — both type 1 and type 2 — put people at risk of developing specific types of cancer, but also that this risk is much higher for women than it is for men.
Women with diabetes are 27 percent likelier to develop cancer, compared with healthy women. By contrast, men with diabetes are 19 percent more likely to develop cancer than healthy men.
And, women with diabetes are 6 percent likelier than men with the same diagnosis to develop a type of cancer.
Specifically, in contrast to men with a diagnosis of diabetes, women with this condition have an 11 percent higher risk of developing kidney cancer, a 13 percent higher risk for oral cancer, and a 14 percent higher chance of developing stomach cancer, as well as a 15 percent higher chance of being diagnosed with leukemia.
One exception was liver cancer, for which men with diabetes have a 12 percent higher risk than women with the same metabolic condition.
"The link between diabetes and the risk of developing cancer is now firmly established."
Dr. Toshiaki Ohkuma
"We have also demonstrated for the first time," he adds, "that women with diabetes are more likely to develop any form of cancer, and have a significantly higher chance of developing kidney, oral, and stomach cancers and leukemia."
'Women are often undertreated'
Why does diabetes raise vulnerability to cancer? The mechanisms that drive this predisposition are still poorly understood. Nevertheless, some researchers argue that overly high levels of blood sugar may damage a person's DNA, thereby heightening their risk of cancer.
And why are women, in particular, more at risk than men? Study co-author Dr. Sanne Peters thinks that this might be due to the fact that women live with prediabetes conditions for 2 years longer than men, on average, which may contribute to exacerbating their vulnerability to cancer.
But there are also other reasons. "Historically," says Dr. Peters, "we know that women are often undertreated when they first present with symptoms of diabetes, are less likely to receive intensive care, and are not taking the same levels of medications as men."
"All of these," she goes on to say, "could go some way into explaining why women are at greater risk of developing cancer. But, without more research we can't be certain." She calls for a more concerted effort to investigate the roots of these sex-specific differences.
"The differences we found are not insignificant and need addressing," Dr. Peters stresses.
"The more we look into gender-specific research the more we are discovering that women are not only undertreated, they also have very different risk factors for a whole host of diseases, including stroke, heart disease, and now diabetes."