The study included 524,089 men and women, ages 20 to 70, who didn’t have cancer or diabetes at the start. By the time half the participants had been in the study for at least seven years, 15,130 people had developed cancer and 26,610 had developed diabetes.
Also, Cho said, “cancer is a highly stressful experience, associated with multiple high-stress episodes such as infections, bleeding episodes, and surgery, that may also increase the risk of diabetes.”
Worldwide, about one in 10 adults have diabetes.
Most have type 2 diabetes, which is associated with obesity and aging and happens when the pancreas can’t properly use or make enough of the hormone insulin to convert blood sugar into energy. Left untreated, diabetes can lead to nerve damage, amputations, blindness, heart disease and strokes.
Time also played a role, with a 47 per cent greater risk of diabetes in the first year or two after a cancer diagnosis. Six to ten years after the cancer diagnosis, the increased diabetes risk was 19 per cent.
The study wasn’t a controlled experiment designed to prove whether or how cancer itself or tumour treatments might directly cause diabetes. It’s also possible that some people in the study had undiagnosed diabetes before they developed cancer, researchers note in JAMA Oncology.
“A significant number of people are living with diabetes, but do not know about it as they have no symptoms,” said Tahseen Chowdhury, a researcher at Royal London Hospital in the U.K. who wasn’t involved in the study.
“A further important factor might be that many of these patients are being seen (by doctors) frequently and having lots of blood tests, which might mean their diabetes is picked up quicker than people who do not have lots of blood tests,” Chowdhury added.