ADA 2010: Diabetes an independent risk factor for vascular disease

New data suggest that although diabetes doubles the risk of vascular disease, elevated fasting glucose has little effect on the risk of coronary heart disease (CHD) or major ischemic events. The results of a meta-analysis of 1.2 million patients in 120 randomized, controlled trials were presented Saturday morning at a special symposium cosponsored by ADA and The Lancet, which published the study in their June 26 issue.

"We've known for decades that diabetes is a risk for vascular disease," said lead author Nadeem Sarwar, PhD, University of Cambridge, United Kingdom. "But how the risk varies by age, sex, and levels of other risk factors remains unknown."

Sarwar represented the Emerging Risk Factors Collaboration, which designed and conducted the study. The collaboration represents more than 12 million person-years of risk, he said, with a mean follow-up of 10 years.

Analysis of contributed studies showed that diabetes roughly doubles the risk of cardiovascular events regardless of other factors. Having diabetes increases the risk of coronary death by 2.31 times and increases the risk of a nonfatal myocardial infarction (MI) by 1.82 times.

The presence of diabetes also increases the risk for ischemic stroke by 2.27 times, for hemorrhagic stroke by 1.56 times, and for other vascular deaths by 1.73 times.

Overall, the hazard ratios (HRs) for CHD were higher for women than for men and higher in younger (40-59 years) patients than in those 70 years old and older. The HRs were also higher for fatal events compared with nonfatal MIs.

Why diabetes produces a greater risk in groups that would be expected to be at lower risk is not clear, Sarwar said. Diabetes may be associated with more severe vascular lesions, but further study is needed.

"We did not see a linear relationship between fasting glucose and cardiovascular disease," Sarwar continued. "The risk is essentially flat for serum glucose between 3.9% and 5.6%, then increases sharply."

The analysis suggests that diabetes is responsible for about 10% of all vascular deaths, roughly 325,000 people annually in the developed world.

"Diabetes doubles the risk for vascular diseases independent of other factors," Sarwar concluded. "In people who do not have diabetes, fasting glucose is not a useful predictor of vascular disease."