Tight glycaemic control may prevent neuropathy in type 1 but not type 2

A foot with ants on it

There remains considerable uncertainty around the exact benefits and harms of tighter control of blood sugars.  This Cochrane systematic review looked at the evidence on neuropathy.

Clinical question:

In diabetes care, does tight glycaemic control prevent neuropathy?

“Tight control” was defined as any intervention to enhance glucose control compared with standard care.  The review’s primary outcome was the incidence of new cases of clinical neuropathy.

The evidence:

Two studies comprising 1,228 patients were found that reported the incidence of neuropathy in type 1 diabetes after five years.  The reviewers calculated a relative risk of 0.46 (95% CI: 0.33 to 0.63) to develop neuropathy in the tight control group compared with usual care.

The combined benefit across the four studies of type 2 diabetes was not statistically significant.

Secondary outcomes generally favoured tight control, but there were significantly more episodes of hypoglycaemia in the tight control patients.  The reviewers concluded:

“The beneficial effect has to be balanced against the significantly increased risk of dangerously low blood sugar levels that can occur in both types of diabetes and which can lead to brain injury amongst other issues.”

Appraisal hints:

  • There were only two studies in the review of type 1, one of which was much larger than the other.  This study had a significant drop-out rate.  It also reported separately on primary prevention and secondary prevention outcomes.  We would want to see more research to increase the confidence of the conclusion.
  • There was a significant increase in the rate of hypoglycaemia in these studies.
  • Several studies were excluded from the primary analysis because they did not report the dichotomous outcome.  Future research should carefully consider the reporting of outcomes.
  • There is important heterogeneity amongst the patient groups and intervention types. This should be considered when interpreting the applicability of this evidence.
  • The individual studies were of variable quality, so there is a risk of bias in the results.
  • There remains considerable uncertainty in this area, in spite of this review.
  • Consider the possible demerits of tight glycaemic control, including increased risk of hypoglycaemia, reduced quality of life, increased anxiety and greater resource use.
  • Future research should also take account of the potential differences between insulin delivery modes in the risk of hypoglycaemia.

Reference:

Callaghan BC, Little AA, Feldman EL, Hughes RAC. Enhanced glucose control for preventing and treating diabetic neuropathy. Cochrane Database of Systematic Reviews 2012, Issue 6. Art. No.: CD007543. DOI: 10.1002/14651858.CD007543.pub2

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Badenoch

Badenoch
I am an information scientist with an interest in making knowledge from systematic research more accessible to people who need it. This means you. I've been attempting this in the area of Evidence-Based Health Care since 1995. So far the results have been mixed. For some reason we expected busy clinicians to search databases and appraise papers instead of seeing patients. We also expected publishers to make the research freely available to the people who paid for it.. Ha! Hence The National Elf service.

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