December 7th, 2009
“As you know I think tight control is a good idea. The clinical study that is going to prove that tight control prevents vascular disease is about halfway done and is looking promising. So let’s stick with your tight control. I don’t want your kidneys to fail.” This was the first I heard of the DCCT study, from Dr. Andrew Drexler, when I lived in New York City and was his patient. They were going to prove tight control is good. It seems obvious to us now, and tight control is the keystone of diabetes therapy in the early 21st century. But it was not always obvious.
We must remember that kids died of type 1 diabetes before insulin was available. They wasted away. So when the Canadians Banting and Best announced that they had found the anti-diabetic hormone there was celebration: when administered to diabetics they seemed to come back to life. They gained weight. They lived.
As therapy developed opinion was divided on on the dosing needed to manage the disease. My grandfather’s diabetes management book from the 1940′s shows that therapy was counting calories and injecting insulin on a predetermined schedule. The only way to determine that the insulin dose was right was to measure urine sugar (which required multiple test tubes and hot water on the stove). Clearly the average blood sugar would have been high by tight control standards.
When I was diagnosed in the 1970′s we were still in the same era: only urine sugars were available at home. (But it no longer required a chemistry set but rather a convenient strip.) I would get a blood sugar measurement every three months — when I visited my doctor! Then home blood glucose testing sets were launched and the new era of management began.
Once it was possible to self-measure blood sugars, interest in the relationship between blood sugar and vascular disease grew. Many thought that blood sugar abnormalities were the cause of diabetic vascular disease which meant that better control would reduce vascular disease. I remember that at the time the most compelling anecdotal evidence came from some of longest lived diabetics. When long acting insulin was introduced some diabetics did not switch but continued to inject pure insulin (what we now call regular insulin). These old-timers tended to have less vascular disease than the more up-to-date diabetics taking long acting insulin. Could it be that a bolus of insulin at meals was better than steady insulin all the time?
The DCCT study was designed to answer that question, and it did in spades. It is rare that a major study in a major disease has such a dramatic outcome. Look at figures 2 through 4. Vascular complications drop dramatically with improved hemoglobin A1c, a measure of average blood sugar. It was clear to all that tight control works. And tight control has been the quest for type 1 diabetics ever since.