The message to diabetics has been remarkably consistent for years: Lower your blood sugar to near-normal levels to protect yourself from deadly and disabling complications.
But the findings of a national study, released last week, suggest that the advice may need to be tempered slightly for diabetics who have heart disease or are at high risk for it because of high blood pressure, high cholesterol, a history of smoking or obesity. In the study, long-term diabetics with those conditions who reduced their blood sugar very close to normal were slightly more likely to die than those who settled for a bit higher level. The leaders of the study, surprised by the findings, cannot explain the increased deaths.
As diabetes specialists search for explanations, they urge patients to consult their doctors before making any adjustments in their treatments. Most diabetics are unable to reduce their blood sugar to near-normal levels with their current treatment, anyway.
The following are more details about the study and its implications for diabetics.
Q: What was the goal of the study?
A: The 10,000-person study, sponsored by the federal government, was designed to examine how best to reduce severe heart disease among long-term Type 2 diabetics at high risk of this complication. It tested three treatment strategies: intensive lowering of blood sugar levels, intensive lowering of blood pressure, and reduction of fat levels in the blood. Type 2 diabetes is the most common form and typically affects adults. About 65 percent of diabetics die from heart disease or stroke.
Q: What happened?
A: Researchers halted the part of the study designed to intensively lower blood sugar after discovering that more of those patients were dying than in the control group. The target of this arm of the study was to get patients' blood sugar to normal levels - or below 6 percent on a measure called hemoglobin A1c - using an intensive regimen of diet, exercise, drugs, and insulin, if necessary.
About half of the participants in the intensive treatment group reduced their A1c levels below 6.4 percent, while a comparison group getting typical care had levels about 7.5 percent - or closer to the typical average for all diabetics. About 14 people per 1,000 in the intensive treatment group died over the four years of the study, compared with 11 per 1,000 in the comparison group. The death rate in both groups was lower than in the overall population of diabetics, which is about 50 per 1,000 per year.
Q: Why did this come as such a surprise?
A: It makes intuitive sense that lowering blood sugar to normal would be best, because the damage to blood vessels in diabetics is thought to be the result of the abnormal levels of sugar in their blood.
Previous studies had also found that reducing A1c to less than 7 percent cut the risk of damage to the eyes, kidney, and nervous system in both Type 2 and Type 1 diabetics. Among Type 1 diabetics, who typically develop the illness as children, reducing the A1c to about 7 percent also cut the risk of heart disease.
What are current treatment guidelines for lowering blood sugar, and will those now be reconsidered, at least for some patients?
The American Diabetes Association recommends that people with Type 2 diabetes keep their blood sugar below 7 percent, but that each patient should consult his or her doctor to set an appropriate goal. The association is standing by the recommendation. However, some leaders of the study said that patients with heart disease or with several risk factors should aim for no lower than 7 percent, rather than near-normal levels.
Q: What about Type 1 diabetics?
A: The study findings do not apply to Type 1 diabetics.
Q: Some of the patients in the study took Avandia, which previous studies suggested raises the risk of heart problems. Could this be why more patients died?
A: Researchers have found no link between Avandia and the higher death rate, or between any drug or combination of drugs and the death rate. They also ruled out a link between extremely low blood sugar, a condition called hypoglycemia, and the deaths.
Q: What other possible explanations are being explored?
A: Researchers are looking to see whether there were any specific characteristics of the participants , whose average age was 62, that could explain the higher rate of deaths. Previous studies were in patients who were younger, recently diagnosed and with no special risk for heart disease. Researchers also plan to reexamine the treatment regimen in more detail to see if they can find anything else that might explain the deaths.
Sources for this report include the National Heart, Lung and Blood Institute; Dr. Martin Abrahamson, medical director of the Joslin Diabetes Center; and leaders of the Action to Control Cardiovascular Risk in Diabetes study.
