Thursday, December 22, 2005
DCCT/EDIC : Glycemic control may decrease cardiovascular risk
For a number of years I have told type 2 diabetics that it is important to control the blood sugar to decrease the risk of damage to the eye, kidneys and nerves but that we needed a different approach to decrease their risk of heart disease. Now the follow up part of the landmark DCCT give us evidence that at least in type 1 diabetics that glycemic control decreases the risk of cardiovascular disease. The decrease in cv disease risk is impressive,in part, because the treatment group enjoyed lowered blood sugar values for only 6.5 years. After that, during the followup period (from 1993 until Feb. 2005) there was little difference in glycemic control.Yet apparently that 6.5 years of better control translated into an impressive 57 % decrease in non fatal MI,stroke and cv disease death. We do not know if this benefit will accrue to type2 diabetics when and if they achieve control such as that seen in the treatment group of the DCCT (glycosylated hemoglobin of 7.4 versus 9.1 in the usual treatment group) but my bet is that it would. You have to wonder what results would have been seen if the Hb A1c values were closer to current treatment goals. I like to poke fun at the RCT religious zealots but a well designed and executed RCT-such as the DCCT- is a thing of beauty.
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2 comments:
[As I posted on MedRants....]
As best as I can tell, the article includes no data about survival rates in each group, and no data about possible adverse effects of tight control (e.g., hypoglycemic events and their consequences) at all.
If one assumes that the decreasing numbers in the groups from the start of the trial to year 11 found in Table 1 represent losses due to mortality, there appears to be no survival advantage from tight control. Given that there were fewer cardiac events in the tight control group, lack of survival advantage may be due to fatal hypoglycemic events in that group.
As I recall, the original DCCT trial showed a marked increase in hypoglycemic events in the tight control group, and thus it was not clear that the trade-off of less microvascular events due to tight control for more hypoglycemic events was favorable to patients.
In the absence of data about total mortality or about hypoglycemic events, this study does not convincingly argue for tight control as the best alternative for patients.
Your points are well taken.There appeared to be no difference in the hemoglobin a1c values in the 11 year follow-up between the two groups suggesting any serious hypoglycemic episodes should have been about the same in each group but the absence of data to that point is a weakness of the study. There were significantly more hypoglycemic episodes in the intensive treatment group during the 6.5 years of the actual trial and part of the cost of decrease in microvascular complications was more hypoglycemia.I agree we should know about total mortality.
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