Cognitive Impairment in Diabetes

When I was in medical school, back in the mid-80's, there was
a bit of a controversy about whether "tight" glucose regulation was a
good idea. Most people thought it was, but there was some concern that
attempts to control the glucose too tightly could lead to increased
risk of complications from getting the glucose too low.

If I recall correctly, the biggest concern was in patients who
had insulin-requiring diabetes, meaning that they either had type-I
diabetes, or that they had severe type-II diabetes.

I'm not an endocrinologist, so someone jump in and tell me if
I'm wrong, but my impression is that there is a consensus now, that
tight regulation is good. 

Now, we see a study that shows a potential neurological risk
to letting the blood sugar vary too much.  That is, the study
shows a higher risk of cognitive impairment, in patients who have
greater fluctuations in blood glucose after meals.

This is from a summary in Medscape (free registration
required):

href="http://www.medscape.com/viewarticle/542385">Postprandial
Glucose Fluctuations Impair Cognitive Functioning



NEW YORK (Reuters Health) Aug 04 - Wide fluctuations in postprandial
glucose are associated with impaired cognitive functioning in older
persons with type 2 diabetes, according to a report in the July issue
of Neurology.



Previous studies have shown that older patients with type 2 diabetes
are more likely than their nondiabetic counterparts to experience
cognitive decline, the authors explain, but the mechanisms remain
unclear.



Dr. A. M. Abbatecola and colleagues from Second University of Naples,
Italy investigated whether postprandial glucose instability was
associated with cognitive functioning in 156 older patients (60 to 78
years old) with type 2 diabetes treated with repaglinide or
glibenclamide (glyburide).



Mini-Mental Status Examination (MMSE) scores correlated with variations
in fasting plasma glucose and postprandial plasma glucose, the authors
report, as did the cognition composite score. The correlations for both
were stronger with increased variability of postprandial plasma glucose.



These associations between greater fluctuations in plasma glucose level
and worse cognitive functioning persisted after adjusting for age,
years of formal education, physical activity, depression, blood
pressure, insulin sensitivity, and body mass index...

I would like to see this replicated in a larger study to feel
more confident in the results, and I certainly would not recommend that
anyone rush out and change their treatment as a result of this one
study.  In general, it is good to be extremely cautious about
changing clinical practice in response to a single study.
 Each study has to be understood in the context of the entire
body of work pertaining to a given topic.



Furthermore, as a psychiatrist, it would be foolish for me to go around
recommending something about a patient's treatment for diabetes.
 I don't claim to have a mastery of the literature on
diabetes.  But, it is important for patients to at least be
aware of findings that could have an impact on the recommendations for
the way their disease is managed.