Selvin E et al. (2005) Glycaemia (haemoglobin A1c) and incident ischaemic stroke: the Atherosclerosis Risk in Communities (ARIC) study. Lancet Neurol 4: 821–826

Increased levels of glycated hemoglobin (Hb A1c) are an indicator of long-term hyperglycemia, which has been implicated in the development of cardiovascular disease. Diabetics have an increased risk of experiencing stroke, but it is not clear whether hyperglycemia contributes to this risk. Selvin et al. examined the effect of Hb A1c levels on the relative risk of stroke in people with and without diabetes, and found that higher levels increased the risk in both groups.

The relationship between Hb A1c concentration and incident ischemic stroke was assessed for 10,886 nondiabetic and 1,635 diabetic participants in the Atherosclerosis Risk in Communities (ARIC) study, with an 8–10 year follow-up. Participants in both groups were analyzed in tertiles based on their Hb A1c concentration. Those found to be most at risk were diabetics with high Hb A1c levels, who were more than four times more likely to suffer stroke than nondiabetics with the lowest blood glucose levels. For nondiabetics, strokes were approximately 1.5 times more likely in participants with high Hb A1c levels than in those with low levels. No clear separation was found between risk for those in the lowest diabetic category and those in the highest nondiabetic category, suggesting that the risk relates more to blood glucose levels than to diabetes itself.

The authors conclude that hyperglycemia could be an independent risk factor for cerebrovascular events in both diabetics and nondiabetics, and that the relationship between Hb A1c and ischemic stroke is similar to that previously reported for cardiovascular disease.