Three decades ago, the landmark Diabetes Control and Complications Study was just beginning. To mark the anniversary of the most important advancement in diabetes care in most of our lifetimes, I’ve been recalling how the study came about and what it revealed. In short, the DCCT proved the tight control of type 1 diabetes not only was an achievable goal, but that it prevented or delayed complications.
But there are questions left. For example, what did the study actually prove? The journal Diabetes Care paid tribute to the anniversary in its January issue, and it summarized the central findings in six points, which are quoted (with commentary) below.
1. Hyperglycemia is the primary modifiable mediator of the long-term complications of T1D.
In other words, high blood sugars are the most important factor in treating diabetes. If you can get them down, you can reduce those long-term issues.
2. Intensive diabetes therapy (INT) with the goal of achieving glucose control as close to normal as safely possible will reduce both the development and progression of diabetic retinopathy, nephropathy, and neuropathy.
The three complications listed there are all microvascular complications of the disease, meaning they start when tiny blood vessels throughout the body are damaged. The exact mechanism of the damage is unclear, but high blood sugars clearly play a role.
3. INT reduces cardiovascular disease in T1D.
The follow-up to the DCCT, an observational study called the Epidemiology of Diabetes Interventions and Complications, is still going on and following some 95 percent of the original patients in the study. The EDIC has shown that tight control seems to reduce the number of cardiovascular problems in patients as they age.
4. The benefits of INT versus conventional therapy persist even after the differences in glycemia achieved have disappeared, so-called metabolic memory.
Keeping your blood sugars down for an extended period of time can keep you healthier years in the future, even if your control worsens. There seems to be some mechanism by which the benefits of tight control keep rolling on through the years.
5. To be most effective, INT should be initiated early in the course of T1D.
A self-explanatory point, for a few reasons. Tight control is easier early on, as patients may still be producing some insulin. For another, it means they establish healthy habits at the very outset of their disease, and are more likely to return to them through the years. It also means that patients are exposed to fewer high blood sugars from the very beginning.
6. Given the current methods of implementing INT, weight gain and an increased risk of severe hypoglycemia are undesirable outcomes.
And here’s the downside. Few health advances come without a couple of unwelcome side effects, and such is the case with tight control. Aggressively monitoring your blood sugar and using insulin does make you more likely to go low, and possibly put on some pounds. But the benefits are certainly worth it.
Finally, a note about average A1c’s. Participants in the DCCT tight-control group managed 7% overall for their years in the study. In the years after it ended, they have averaged 8%. So despite the education they had and the work they did, these groundbreaking patients have found it difficult to sustain optimal A1c levels (many doctors today would even say that average of 7% was too high).
It’s not impossible to achieve great A1c’s on a regular basis, of course. But it is important to recognize that, even with the value of low levels firmly established, many people find treating and handling this disease a continuing challenge. The revolution started by the DCCT isn’t over. It’s still going on, and we’re all part of it.