In the 1950s, about 1 in 5 people died within 20 years after being diagnosed with type 1 diabetes, formerly known as juvenile diabetes. Almost all of them developed diabetic retinopathy, which accounted for about 12% of new cases of blindness between the ages of 45 and 74. People with diabetes relied on inaccurate urine tests to track their blood sugar. They used crude animal-derived insulins to control it.
In 1983, NIH began the Diabetes Control and Complications Trial, which enrolled 1,441 people with type 1 diabetes. This landmark study was stopped early because the results so clearly showed that careful control of blood sugar reduced eye, kidney, and nerve complications by 50% to 75%. In a follow-up study 10 years later, researchers learned that rates of heart disease and stroke had declined by half.
Today, people with type 1 diabetes are living longer and healthier lives. New technologies help them keep tight control of their blood sugar using continuous glucose monitors and insulin pumps that deliver rapid-acting, bioengineered human insulin.
We also know a lot more about type 2 diabetes. We know that family history, obesity, and physical inactivity are risk factors for this condition, formerly known as adult-onset diabetes. NIH-funded research has shown that type 2 diabetes can be delayed or prevented. Basic lifestyle interventions—modest weight loss and regular exercise—slash type 2 diabetes risk by 58% over 3 years in people with pre-diabetes. Despite this good news, type 2 diabetes still accounts for 90% of diabetes cases nationwide and has been increasing at an alarming rate due to the rise in obesity in the United States.
Adults with type 2 diabetes are over twice as likely to die from heart disease as those without diabetes. But studies about how tightly to manage blood pressure and lipid levels have been inconclusive. Two related clinical trials will now help guide doctors.
The landmark Action to Control Cardiovascular Risk in Diabetes (ACCORD) clinical trial is one of the largest studies ever conducted in adults with type 2 diabetes who are at especially high risk of cardiovascular events, such as heart attacks, stroke or death from cardiovascular disease. The multicenter clinical trial tested 3 strategies to lower the risk of major cardiovascular events: intensive control of blood sugar, intensive control of blood pressure and treatment of multiple blood lipids.
ACCORD researchers from 77 medical centers in the United States and Canada studied over 10,000 participants between the ages of 40 and 79 who had type 2 diabetes for an average of 10 years. The participants had pre-existing cardiovascular disease, evidence of subclinical cardiovascular disease, or at least 2 cardiovascular disease risk factors in addition to diabetes. All the participants were enrolled in the ACCORD blood sugar treatment clinical trial and maintained good control of blood sugar levels during the study. In addition, participants were enrolled in either the blood pressure trial or the lipid trial and were treated and followed for an average of about 5 years. The study was sponsored primarily by NIH’s National Heart, Lung and Blood Institute (NHLBI).
Results of the ACCORD blood sugar clinical trial were reported in 2008. That trial found that intensively lowering blood sugar to near-normal levels brought a higher risk of death for participants than standard blood sugar control.
The latest results appeared online in 2 reports on March 14, 2010, in the New England Journal of Medicine. In the blood pressure trial, researchers randomly assigned over 4,700 participants with elevated blood pressure to a target systolic blood pressure of either less than 140 mmHg (the standard group) or a normal level of less than 120 mmHg (the intensive group). A variety of medications was used to reach blood pressure goals. The study found that lowering blood pressure to normal levels doesn’t significantly reduce the risk of cardiovascular events overall, although it may reduce the risk of stroke.
In the lipid trial, researchers compared the cardiovascular effects of a statin (simvastatin) to combination therapy of a statin and a fibrate (fenofibrate) in over 5,500 participants. Both statins and fibrates are used to treat abnormal levels of blood lipids. Statins lower LDL, or “bad” cholesterol, and are proven to lower cardiovascular disease risk in people with diabetes. Fibrates primarily lower fats in the blood known as triglycerides and raise HDL, or “good,” cholesterol.
Combination therapy appeared to be safe, but didn’t lower the risk of heart attack, stroke or death from cardiovascular disease more than statins alone. “Although our analysis suggests that certain patients may benefit from combination therapy, this study provides important information that should spare many people with diabetes unneeded therapy with fibrates,” says Dr. Henry Ginsberg of Columbia University, lead author of the lipid trial.
“ACCORD provides important evidence to help guide treatment recommendations for adults with type 2 diabetes who have had a heart attack or stroke or who are otherwise at especially high risk for cardiovascular disease,” says acting NHLBI director Dr. Susan B. Shurin.
It’s important to note that the treatments used in the standard control groups have previously been shown to be effective. The findings don’t detract from the fact that controlling blood pressure and LDL cholesterol levels can reduce cardiovascular risk—not only for people with diabetes, but for everyone.
For more information, visit the National Institutes of Health (NIH) at www.nih.gov.
