(Published in Stroke. 2006;37:1413.)
Patients with impaired glucose tolerance have moderate elevations of blood glucose, but the elevations are not severe enough for them to be diagnosed with diabetes mellitus. Dr. Vermeer et al. studied 3,127 TIA or minor stroke patients who participated in the Dutch TIA Trial. Baseline non-fasting glucose levels were obtained in all patients. After a 2.6 year follow-up, 9% of the patients experienced a stroke and 6% a heart attack or cardiac death. Those whose blood sugars diagnosed them with diabetes had a nearly tripled risk of stroke, compared with those with normal blood sugars. Patients with moderate levels of glucose elevation (impaired glucose tolerance) had nearly double the risk of stroke as those with normal glucose levels. Interestingly, patients with lower than normal blood glucose levels had about a 50% increased risk of stroke compared to those with normal glucose levels. There was no increased risk of heart attack or cardiac death related to glucose levels.
Diabetes has been a well-established risk factor for ischemic stroke for many years, and it was surely suspected that lesser degrees of glucose elevation would confer some increased risk. This study demonstrates that the risk of impaired glucose tolerance is significant and deserves to be evaluated in patients who have suffered from an ischemic stroke or TIA. For my part, I will begin to routinely test my non-diabetic stroke patients for impaired glucose tolerance.
This situation is similar to what has occurred regarding glucose levels and peripheral neuropathy. Patients with diabetes are known to suffer from nerve damage, often causing numbness of the feet and sometimes associated pain. It was later noted that even lesser glucose elevations (impaired glucose tolerance) could cause this nerve damage. Now neurologists routinely screen for impaired glucose tolerance in those patients with otherwise unexplained neuropathy.
How should impaired glucose tolerance be treated? Some endocrinologists would recommend adding an oral hypoglycemic agent, typically used to treat diabetes, to keep a patient's blood sugars at a lower overall level. The risk, though, is that at some points in the day, blood sugar levels may go very low, which can be dangerous. Another approach is simply to have patients follow a diabetic diet, low in carbohydrates, to avoid peaks in blood sugar. Certainly, in the long-term, patients need to be advised to achieve their ideal weight, since impaired glucose tolerance might be reversible by this means.