Nocturnal hypos linked to heart rhythm problems in Type 2 diabetes

Night-time hypos may increase the risk of abnormal and potentially dangerous heartbeat rhythms in people with Type 2 diabetes on insulin therapy, according to a new study.

The research, published in the journal Diabetes, suggests the increased risk of abnormal rates and/or rhythms of heartbeat (arrhythmias) – particularly at night – may be a contributing factor for sudden cardiac death in those with Type 2 diabetes who are also at high cardiovascular risk. The findings may also shed light on sudden deaths in Type 1 diabetes patients, who often experience high rates of nocturnal hypoglycaemia.

The study authors concluded that hypoglycaemia is common and frequently unrecognised in people with advanced Type 2 diabetes. They warn that hypoglycaemia should be minimised in those with high cardiovascular risk, as arrhythmias may contribute to increased cardiovascular mortality in this susceptible patient population.

Senior author of the study, Dr Simon Heller, of the University of Sheffield, said: “What we’ve found is potentially important in explaining a possible mechanism by which hypoglycaemia can lead to prolonged, slow heart rates that disturb blood flow to the heart and can result in a lethal cardiovascular event.

“Hypoglycaemia is not widely reported in patients with type 2 diabetes,” he added, noting that older patients with Type 2 diabetes in his study did not report symptoms of hypoglycaemia or arrhythmias – they were only detected because they were being monitored.

He concluded: “In the older group with a known history of cardiovascular disease, this might turn out to be something to be very concerned about.”

The study involved 25 older people with Type 2 diabetes who had a history of cardiovascular disease and had been on insulin therapy for at least four years. The investigating team used continuous glucose monitoring and ECGs to track blood glucose levels and heart rates over the course of a week. They were surprised how frequently hypoglycaemia occurred overnight and the fact that it sometimes lasted several hours. When this occurred, people also registered prolonged periods of very slow heart rate rhythms.

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