Can An Insulin Pump Protect Diabetics from Heart Disease?
With commentary by lead study researcher Isabelle Steineck, MD, an endocrinologist at Denmark’s Aarhus University Hospital
People with type 1 diabetes who used an insulin pump to control their blood sugar were 58% less likely to have a fatal heart attack, stroke or other deadly cardiovascular disease than those who gave themselves daily insulin injections in a recent, 6.8-year study published in the British Medical Journal. Insulin “pumpers” were also 73% less likely to die from any cause.
Lead researcher Isabelle Steineck, MD, an endocrinologist at Denmark’s Aarhus University Hospital and colleagues tracked the health of 18,168 people with type 1 diabetes from the Swedish National Diabetes Register; 2,441 used insulin pump therapy and the rest had multiple daily insulin injections. While blood glucose levels in the two groups were the same – with an average A1c of 8% — Dr. Steineck says that the insulin-pump group likely had fewer periods of extremely low glucose levels (hypoglycemia) and high glucose levels (hyperglycemia) that affect the heart and arteries in dangerous, though very different, ways.
“I believe hypoglycemia is one of the most important mediating factors for our results,” she told EndocrineWeb in an email interview. Low blood sugar can trigger off-beat heart rhythms (cardiac arrhythmias) and the rupture of plaque packed into the walls of arteries in the heart, recent research shows. In a 2014 study, by researchers from Sweden’s University of Gothenburg who also worked on this new insulin-pump study, people with type 1 diabetes and a history of severe hypoglycemia were 79% more likely to die in the month after a heart attack or stroke than those whose blood sugar stayed on a more even keel.
Dr. Steineck notes that insulin pump therapy may also have reduced risk for episodes of high blood sugar – hyperglycemia – that over time contribute to the build-up of plaque in artery walls. In addition, the insulin pump group may also have enjoyed a lower mortality risk because they had received extensive training in order to use one – including education on the importance of performing regular blood-glucose monitoring and interpreting the results.
People with type 1 diabetes face a two- to five-fold higher risk for heart disease and up to a 7-fold higher risk for stroke than those without this condition, according to a 2014 report from the American Diabetes Association and American Heart Association. Nerve damage caused by the disease can interfere with healthy heart function, while high blood sugar can boost levels of body wide inflammation in ways that make arteries less flexible, add plaque to artery walls and even promote the formation of heart- and brain-threatening blood clots, the groups say. Keeping blood sugar within a healthy range along with maintaining a healthy weight, following a healthy diet, getting exercise, not smoking and controlling blood pressure and cholesterol are important for reducing risk, the report notes.
An insulin pump is a small, computerized device worn on the body, with a flexible tube and needle-like catheter inserted into the fatty tissue below the surface of your skin, usually at the abdomen. The pump delivers a small, continuous “basal” dose of insulin as well as larger “bolus” doses before meals to cover the rise in blood sugar after eating. Users have to do frequent blood-sugar checks, count carbohydrates and adjust their insulin doses to match changing glucose levels, the amount of carbohydrates you plan to eat and the amount of physical activity you’re getting. A 2010 review of 23 studies comparing pumps with insulin injections in people with type 1 diabetes concluded that pumping can lead to better blood-sugar control and may reduce episodes of low blood sugar.
Right now, an estimated 350,000 to 500,000 Americans with type 1 diabetes (less than one-third of the 1.8 million with type 1 use a pump, according to a 2014 report from the American Academy of Clinical Endocrinologists and the American College of Endocrinology. You may be a good candidate for “pumping”, the groups say, if you have type 1 diabetes, receive four or more insulin injections and four or more blood glucose checks daily and feel ready and able to learn how to use and maintain the device.
Insulin Pump vs. Injections
Should people with type 1 also use an insulin pump, instead of injections, for heart protection? “Available evidence certainly strongly indicate all persons with type 1 diabetes should consider the cons and pros with a pump instead of daily injections,” Dr. Steineck says. “Personally I think that more persons with type 1 diabetes could benefit from using insulin pump as long as they get all the right education about the pump and are able to understand how to use it.”
But endocrinologist Grazia Aleppo MD, FACE, FACP, associate professor of medicine at Northwestern University in Chicago, IL, and a member of the EndocrineWeb Editorial Board, cautions that the study is observational and doesn’t prove that using an insulin pump prevents cardiovascular disease deaths. The results, she told EndocrineWeb, likely reflect differences between the two groups rather than the effects of using an insulin pump versus multiple daily insulin injections.
“The cohort on insulin pump was younger, had shorter duration of diabetes and developed diabetes at a later age. Fewer were taking blood pressure medication, there was a smaller percentage of smokers, they were more physically active, and had higher level of education. In addition, the insulin pump cohort had fewer subjects with microalbuminuria (which detects the presence of protein in the urine), which is a predisposing risk to heart disease and is correlated with increased mortality in these subjects. The insulin pump users also had smaller percentage of pre-existing heart disease and congestive heart failure. So, overall, one could say that the population on an insulin pump was healthier,” Dr. Aleppo notes. The insulin-pump group may also have been more motivated to monitor and control their glucose levels, she adds.