It's a question that has concerned people with diabetes for years: Does long-term use of insulin cause heart disease?

An estimated 26 million children and adults in the United States have diabetes. It's a chronic condition in which the body can't produce insulin or can't properly use the insulin it does manage to produce.

In a new study published in the New England Journal of Medicine, researchers followed more than 12,000 people in 40 countries for 6 years. Some were pre-diabetic, others were already diagnosed with Type 2 diabetes. Half of the patients were treated with insulin and the rest were not.

The results: There was no difference between the two groups when it came to cardiovascular health, including heart attacks and strokes or in the development of any type of cancer. The study did confirm two previously known side effects of insulin use: low blood sugar and modest weight gain.