The figure of 7.8mmol/ml is the same as the 140mg/dl in the American College of Endocrinology 2002 guidelines.
Interestingly the American Diabetes association don't have a post prandial figure on their website anymore (it used to be high at 10mmol/l) They now say
" Postprandial glucose may be targeted if A1C goals are not met despite reaching preprandial glucose goal"
http://www.diabetes.org/living-with-dia ... ucose.html
So the emphasis is on HbA1c not post prandial spikes.
Whether spikes cause damage over and above that associated with high average levels is a matter of huge debate and there is very little hard data
.In vitro (ie cells in test tubes) studies do show damage caused by short term glucose exposure
Summarizing, in vitro studies do show a relationship between glycemic variability and oxidative stress-induced apoptosis and renal cell proliferation in cultured human or rat cells. These findings are confirmed in an animal study, but this relation could not be consistently reproduced in human studies. Differences in duration and frequency of the periods with alternating glycemia as well as differences in methods used for oxidative stress quantification are possible explanations for these discrepant findings
Results from long and medium term trials don't show much association between the day to day ups and downs and diabetic complications. To be honest there are few medium term trials and only two very long term ones DCCT ;T1 and the UKPDS ;T2 . The first one had seven point glucose profiles measured once every three months over 20+ years , the second one didn't look at daily glucose only HbA1c. So we don't really have much evidence . The limited evidence from the DCCT found that day to day variability didn't make a difference. It was overall glucose patterns that mattered.
We can draw a few conclusions from these studies. First, a relation between short-term glucose variability and microvascular or neurological complications has not been proven in type 1 diabetes patients and has not been investigated in type 2 diabetes. Second, no studies have been performed investigating the influence of glucose variability on macrovascular complications and death in either type 1 or type 2 diabetes patients, but the HEART2D trial suggests that lowering glucose variability does not improve cardiovascular outcome in type 2 diabetes patients after acute myocardial infarction. In contrast, glucose variability is clearly related to mortality in critically ill patients without diabetes, but intervention trials are still lacking
One complication which is definitely affected by glucose variability is hypoglycemia in insulin treated diabetics.
From the above, it can be concluded that glucose variability is larger in patients with diabetes who suffer from hypoglycemia, in particular severe hypoglycemia. Also, glucose variability seems a predictor of severe hypoglycemia, but it is more difficult to answer the question whether it is an independent predictor of future hypoglycemia
http://edrv.endojournals.org/content/31/2/171.full
What has been shown to matter is the HbA1c, the average glucose (subtly different) and whether that is high or varies considerably (ie high HbA1c followed by low followed by high over the years.
There are several studies that show that this up and down over time seems affect outcomes.
Here is a 2012 summary from a British researcher (the earlier paper was a 2009 one) I was trying to find a later paper that might have given some more recent evidence. It is a short communication in response to another paper so isn't in depth.
....The distinction between these definitions is of relevance because definitively showing an association between increasing short-term glycaemic variability and an additional risk of micro-or macrovascular complications has so far proved to be elusive. Retrospective data analyses of the Diabetes Control and Complications Trial (DCCT) have shown little signal that within-day variability is important in the development of microvascular complications [2–4]. However, this study was not originally designed to address this question.
Although postprandial hyperglycaemia (a subset of glucose variability) is generally regarded as a risk marker for cardiovascular disease [5], the only prospective study to specifically assess whether reducing within-day glycaemia might influence cardiovascular events has been unable show any benefit [6].
E. S. Kilpatrick (*)
Department of Clinical Biochemistry, Hull Royal Infirmary,
Diabetologia (2012) 55:2089–2091
DOI 10.1007/s00125-012-2610-5
Pragmatically, I doubt anyone can achieve lowish HbA1cs without relatively good control of post prandial spikes. However so far there isn't a lot of evidence to suggest that some interday variability is a risk factor (except perhaps in the case of pregnant women and critically ill patients in ICU which are very specific cases.)
This may change as more studies use continuous monitoring but I can't see anyone funding a long term trial with large numbers of subjects using it .
