The research was led by a team from the University of Pittsburgh Graduate School of Public Health and was published online on 7 June in the New England Journal of Medicine, NEJM. It was also presented at the American Diabetes Association 69th Scientific Sessions.
The researchers also found that the risk of a further major cardiac event was lowered when diabetes patients with more severe heart disease had prompt bypass surgery.
Many of the 20 million Americans with type 2 diabetes also have heart disease said lead investigator Dr Sheryl F. Kelsey, professor of epidemiology at the University of Pittsburgh Graduate School of Public Health, explaining that:
"We began this study because we don't know how best to treat this deadly duo that is affecting more and more people at increasingly younger ages."
Kelsey said their findings will provide much needed guidance on how to treat patients with both diseases.
Called BARI 2D (short for Bypass Angioplasty Revascularization Investigation 2 Diabetes), the study started in 2001 when it signed up 2,368 patients who had both type 2 diabetes and stable heart disease and who were being treated by their doctor for cholesterol and blood pressure.
The researchers randomly assigned each participant to one of two groups. One group received drugs and underwent prompt surgery to restore blood flow: this comprised either angioplasty (where a balloon is inflated inside a blocked blood vessel) or bypass surgery (where the blood vessels are cut away and re-connected to bypass the blocked artery). The other group just received drugs.
Across the two groups there was also another split: there were two types of drug therapy, one where the patient received insulin and the other where the patient's resistance to insulin was lowered (using metformin or rosiglitazone) and the researchers analysed which of these treatments led to better outcomes.
They did not however compare angioplasty and bypass surgery, the point of the study was to compare prompt surgery and drugs on their own.
The results showed that:
- 5-year survival rates did not differ significantly between the surgery with drugs group (88.3 per cent) and the drugs only group (87.8 per cent).
- There was also no significant difference in survival between those who received insulin (87.9 per cent) and those who had drugs to reduce insulin resistance (88.2 per cent).
- But the group that had bypass surgery had fewer patients experiencing major cardiovascular events such as heart attacks, stroke and deaths (22.4 per cent) than the drugs only group (30.5 per cent).
- And the lower risk of further cardiovascular events appeared to be more likely among those who had bypass surgery and the drugs that reduced insulin resistance.
"We observed that patients with more severe heart disease did better over time when they received bypass early compared to those who received drug therapy alone."
"Those who underwent bypass surgery seemed to do particularly well on insulin-sensitizing drugs," he added.
But he cautioned that this result should be treated as "preliminary because we did not set out to answer this question with our study design".
Dr Saul Genuth, director of the BARI 2D diabetes management center and professor of medicine at Case Western Reserve University said that overall the study is reassuring in that it confirms the current drug therapies for treating diabetes are appropriate and it also suggests that:
"When a patient with type 2 diabetes has more severe heart disease it may be better to do bypass surgery early than to wait and simply treat with medication."
"For patients with milder disease who are candidates for angioplasty, it is appropriate to treat with drug therapy first," he added.
"A Randomized Trial of Therapies for Type 2 Diabetes and Coronary Artery Disease.
The BARI 2D Study Group.
Source: University of Pittsburgh Schools of the Health Sciences.
Written by: Catharine Paddock, PhD