Some people with type 2 diabetes might want to rethink how they manage their disease, based on a trio of new studies showing that tightly controlling blood glucose levels doesn't reduce cardiovascular disease in people at high risk, perhaps because they have high blood pressure or are overweight. Reaching blood pressure and cholesterol goals rather than blood glucose targets may be more important in preventing heart attack and stroke in these people, say experts. In those who are newly diagnosed with diabetes and are not already in the high-risk category, intensively managing blood sugar may be effective at reducing heart risk.
Cardiovascular problems account for about two-thirds of deaths in people with type 2 diabetes, and it has long been thought that if patients' A1C levels—a measure of average blood sugar over the preceding two to three months—could be reduced to about 6 percent, the high end of normal for nondiabetics, many cardiovascular complications could be reduced or avoided. Current treatment guidelines call for people with type 2 diabetes to maintain A1C levels of 7 percent or lower, but in the United States the actual average is closer to 7.8 percent, according to Ann Albright, president of healthcare and education for the American Diabetes Association.
The latest studies—of more than 23,000 people with type 2 diabetes—all tried to determine whether using oral drugs and insulin to bring A1C levels down to the 6 percent range reduced cardiovascular events such as heart attack, stroke, and death. Subjects were generally in their 60s, had had diabetes for several years, and had A1C levels above 7 percent. About a third had already had a cardio event like a heart attack or stroke, and many were at high risk for cardiovascular problems because they had high blood pressure or cholesterol, smoked, or were obese.
Subjects were divided into two groups. One received intensive treatment aimed at reducing A1C to as low as 6 percent; a control group received standard treatment. The studies tracked participants for at least five years, although one study, sponsored by the National Heart, Lung, and Blood Institute, halted the intensive treatment portion of the study in February after just 3.5 years when it was found that this group had a 22 percent increased risk of death compared to the standard group. Researchers presented the findings of the three trials—the NHLBI's ACCORD study, the ADVANCE study conducted by researchers for the George Institute for International Health in Australia, and the VA Diabetes Trial—at the American Diabetes Association's 68th annual scientific sessions in San Francisco this week.
The studies' results should not be interpreted as a license to ignore blood glucose levels, researchers warn. Although tight glycemic control didn't reduce cardiovascular problems in high-risk individuals, maintaining healthy blood sugar levels remains important for preventing microvascular complications, including kidney, eye, and nerve damage. In fact, the ADVANCE trial found a 21 percent reduction in kidney disease risk among those whose blood sugar was managed intensively.
Moreover, many Americans with type 2 diabetes have a long way to go to reach the 7 percent target—never mind aiming lower. "My fear is that the typical diabetes person with type 2 and an A1C of 8.5 will say, 'I don't need to focus on my A1C,'" says Tom Boyer, executive director of the Diabetes Care Coalition, an educational organization sponsored by the ADA and other diabetes groups. "What these studies say is that A1C needs to be kept at near normal levels but not go too low."
It's unclear why participants in the NHLBI's intensive group with stricter A1C controls faced a higher risk of death. The two other studies did not report a similar increased mortality risk.
Rather than demonstrating that one type of treatment is more useful than another, these studies show that there's no one-size-fits-all solution, experts say. "You have to individualize your treatment goals," says Martin Abrahamson, medical director of the Joslin Diabetes Center in Boston. "You have to take into account who the patient is, and what other co-morbidities they have, and their projected life span, and so on."