ADA: Diabetes doubles risk of heart attack, stroke

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Having diabetes approximately doubles the risk of developing a range of blood vessel disease states, including heart attacks and strokes, according to a study published June 24 in Lancet, and presented at the American Diabetes Association (ADA) conference in Orlando, Fla. Diabetes is estimated to be responsible for one in every 10 deaths from cardiovascular disease, or about 325,000 cardiovascular deaths annually in all industrialized countries combined.

The study results come from an analysis of 700,000 people, each of whom was monitored for about a decade in 102 surveys conducted in 25 countries, as part of an international consortium led by Nadeem Sarwar, PhD, and John Danesh, DPhil, from the University of Cambridge in England.

Cardiovascular disease is the leading cause of death globally, responsible for about 17 million deaths annually. Diabetes has long been long recognized as a risk factor for cardiovascular disease, but, according to the authors, the extent of its effect on different blood vessel diseases has been debated, along with how much of the effect of diabetes on blood vessel diseases is due to higher levels of blood fats, blood pressure and obesity.

The researchers said that “surprisingly,” only a small part of the effects of diabetes was explained by blood fats, blood pressure and obesity. This finding suggests that diabetes may exert its harms through additional routes.

"Our findings highlight the need for better prevention of diabetes coupled with greater investigation of the mechanisms by which diabetes increases the risk of cardiovascular disease," Sarwar said.

The study also found that in people without diabetes, higher-than-average fasting blood glucose levels were only weakly related to subsequent development of heart attack or strokes. This finding argues against using information on blood glucose levels to help identify people at higher risk of heart attack or stroke, Sarwar, Danesh and colleagues reported.

"Information on age, sex, smoking habits, blood pressure and blood fats is routinely collected to assess risk of developing cardiovascular disease,” Sarwar said. “Our findings indicate that adding information on fasting blood glucose levels in people without diabetes does not provide significant extra help in assessing cardiovascular risk."

In an accompanying commentary, Hertzel C. Gerstein, MD, from the McMaster University and Hamilton Health Sciences in Hamilton, Ontario, wrote that the progressive relationship between blood sugar levels above the normal range and vascular outcomes could be linked to and/or magnified by a wide range of other factors, including lipid metabolism, fat deposition into tissue and liver function among others.

"Any or all of these factors (and others) might promote cardiovascular disease through various known and unknown mechanisms. Large long-term clinical trials of insulin-replacement therapy, incretins and other approaches targeting one or more of these abnormalities that are either underway or about to start are certain to shed more light on the link between dysglycemia and serious outcomes," Gerstein wrote.