Posted: Mar 2, 2011 11:30 PM
March 2, 2011 -- Diabetes roughly doubles the risk of having a heart attack or stroke, a reality that's put many doctors and patients on alert about the need to closely watch blood pressure, cholesterol, and other harbingers of an ailing cardiovascular system.
But less attention has been paid to other ways diabetes may cut life short.
Now an international team of researchers has produced one of the first comprehensive reports on the non-cardiovascular causes of death in people with diabetes, and it offers some sobering new findings.
Pooling data from 97 studies representing more than 820,000 people, researchers found that 40% of people with high blood sugar died from non-cardiovascular causes.
For example, compared to people who had not been diagnosed with diabetes, those with diabetes had triple the odds of dying of kidney disease and more than double the risk of dying of an infection (excluding pneumonia) or from liver cancer.
Risks of dying from other kinds of cancers, including ovarian, pancreatic, colorectal, breast, bladder, and lung, were also increased, though more modestly.
Diabetes also increases the risk of dying from Alzheimer's disease, chronic obstructive pulmonary disease (COPD), falls, nervous system disorders, digestive disorders, suicide, and liver disease, to name a few.
Those risks remained even after researchers accounted for the effects of other influences on the risk of death like body mass index (BMI), age, sex, and smoking.
The study is published in the New England Journal of Medicine.
"We've known that people with diabetes live shorter lives. That, I think, is not new," says Spyros Mezitis, MD, an endocrinologist at Lenox Hill Hospital in New York City.
"Cardiovascular [disease] is what we all are worried about with diabetes," says Mezitis, who was not involved in the study. "But [the researchers] go into cancer and non-cancer [causes], infectious diseases, and other causes and they say there's an increased association with those diseases."
Previous studies, going back to the 1960s, have noted that diabetes and cancer were found in the same person more often that would be expected by chance.
"We were in some way expecting this finding, but of course, this is quite a major advance in the science process to quantify many of these questions," says study researcher Emanuele Di Angelantonio, MD, a university lecturer in the department of public health and primary care at Cambridge University in the U.K.
Other experts agree.
"This result highlights the importance of continued work on why diabetes increases cancer risk," says Edward Giovannucci, MD, ScD, a professor in the departments of nutrition and epidemiology at Harvard School of Public Health in Boston.
"I think it is good that this area is receiving more attention because besides smoking, obesity, physical inactivity, related problems such as diabetes are likely to be close to importance as smoking for cancer risk," says Giovannucci, who was the lead author of a consensus statement jointly published by the American Cancer Society and the American Diabetes Association in 2010.
Though it's not clear exactly how diabetes may increase cancer risk, the consensus statement notes: "The relative risks imparted by diabetes are greatest (about twofold or higher) for cancers of the liver, pancreas, and endometrium, and lesser (about 1.2-1.5 fold) for cancers of the colon and rectum, breast, and bladder. Other cancers (e.g., lung) do not appear to be associated with an increased risk in diabetes, and the evidence for others (e.g., kidney, non-Hodgkin lymphoma) is inconclusive. Few studies have explored links with type 1 diabetes."
One common link may be insulin.
Often before people become diabetic, their bodies crank out ever higher levels of insulin because their cells stop responding to it, a condition called insulin resistance.
Insulin also contributes to inflammation, another process that can drive cancer.
"The main message for patients and doctors is probably we should think about non-vascular death," says Di Angelantonio. "We should consider appropriate screening for cancer in patients with diabetes."