There is a threshold blood glucose range beyond which the risk of future stroke or heart attack is increased in people with diabetes who have had a stroke, suggests a new study from Korea, published in the journal Neurology. This optimal range, as estimated by HbA1c, was below 6.8%–7.0%.

The study population included 18,567 individuals with diabetes, who had been hospitalized with a transient ischemic attack or an acute ischemic stroke within a week of onset of symptoms. The retrospective study sourced data from the stroke registry of the Clinical Research Center for Stroke in Korea.

HbA1c was tested for each participant at the time of study entry and the average A1c was found to be 7.5%. The association between admission HbA1c and subsequent risk of vascular events, including stroke, myocardial infarction (MI), and vascular death was evaluated during one-year follow-up.

Results showed that 1437 (8%) diabetic individuals suffered a heart attack or died from vascular disease within a year, while 954 (5%) had a second stroke. Baseline A1c level higher than the 6.8% to 7.0% threshold was associated with a higher risk of an acute cardiovascular event (myocardial infarction) and developing another stroke. The influence of admission HbA1c level on the risk of composite vascular events was particularly seen among those in whom fasting glucose at admission was ≤130 mg/dL. This association persisted even after adjusting for factors like age and sex. The participants had a 27% higher risk for a heart attack and 28% higher risk for having another stroke with baseline A1c more than 7.0% compared to those who had been hospitalized with A1c levels below 6.5%.

The baseline A1c also varied according to the subtype of the ischemic stroke. A1c for the small vessel occlusion subtype was the lowest at 6.6, while it was 7.3 for the large artery atherosclerosis and 7.4 for the cardioembolic subtype of the ischemic stroke.

Diabetes is a known risk factor for stroke. This study has demonstrated an association of admission A1c with the risk of vascular events and the A1c level differed according to the subtype of the ischemic stroke.

Although this study measured only the baseline blood glucose levels with no follow up levels assessed, it adds to the evidence and reiterates the importance of keeping blood glucose under control, particularly if the patient has already had a stroke.

Reference

1. Chang JY, et al. Association of prestroke glycemic control with vascular events during 1-year follow-up. Neurology. 2021 Sep 29;10.1212/WNL.0000000000012729. doi: 10.1212/WNL.0000000000012729.