The study skfinkel is talking about is the ACCORD study which is going to be published in the NEJM in a few days. There’s a press release about it at http://www.nih.gov/news/health/jun2008/nhlbi-06.htm. The participants were Type II diabetics, 40 to 79 years old, with “pre-existing heart disease or at least two cardiovascular disease risk factors”, and tight control was not found to decrease the risk of heart attack or stroke. There is a lot of hullabaloo about this finding in the press because it is very unexpected (although the evidence for a connection between macrovascular disease [e.g. heart attacks] and prolonged high blood sugar in Type II diabetics has never been as strong as it is for microvascular disease [kidney, retina, etc.]).
However, I think there is a major problem with the conclusion, namely the pre-existing risk factors. By the time most Type II diabetics are diagnosed, they have often had elevated blood sugar for years; if they also have other cardiovascular risk factors or frank heart disease, it may be too late for tight blood sugar control to have much effect on the subsequent risk of a heart attack or stroke, especially if they are not doing anything to modify other risk factors (cholesterol, obesity, etc.).
In other words, we don’t know what the results would be if tight control were introduced as soon as blood sugar levels began to rise in these patients, or at least before the development of other cardiovascular risk factors. In Type I diabetes, tight control HAS been shown to significantly reduce heart attacks, strokes, and deaths from cardiovascular disease (article is free at http://content.nejm.org/cgi/content/full/353/25/2643). The patients in this study were 13 to 40 when the study began and did not start out with heart disease or years of totally untreated elevated blood sugar. So, I think this suggests what might happen if an early intervention of Type IIs were attempted.
And very importantly (this, I think is not being emphasized nearly enough in the news), tight control DOES lower the risk of all the terrible microvascular complications of diabetes: retinopathy (leading to blindness), nephropathy (leading to kidney failure), peripheral vascular disease (leading to pain, terrible wounds, amputation), etc.
Just my two cents – and I realize this wasn’t what the original questions was – as to that, Type I diabetics, who don’t have any insulin insensitivity, can eat as much sugar as they want as long as they take enough insulin, although it requires a lot of blood sugar checking.