A Large Danish Study Finds Diabetes Significantly Raises the Risk of Sudden Cardiac Death
Cardiology > Diabetes
— The risk is especially pronounced among younger adults, researchers note
December 5, 2025 - 5 min read
A nationwide Danish analysis shows that the chance of sudden cardiac death is markedly higher for people with diabetes, with the elevation most evident in younger individuals and those who require insulin.
In a comprehensive review of every death recorded in Denmark in 2010, researchers found that sudden cardiac death occurred at 3.7 times the rate in people with type 1 diabetes and 6.5 times the rate in people with type 2 diabetes, compared with the general population without diabetes.
Per 100,000 person-years, the incidence stood at 394 for type 1 diabetes, 681 for type 2 diabetes, and 105 for the general population. The study was led by Tobias Skjelbred, MD, of Copenhagen University Hospital in Denmark and published in the European Heart Journal.
“The increased risk was most striking in young individuals with diabetes,” the authors wrote. Their analysis identified 6,862 total cases of sudden cardiac death. Among those with type 1 diabetes, the highest risk occurred in ages 30–40, where the risk reached 22.7 times higher than the general population (95% CI 19.3–26.5). For those with type 2 diabetes, the highest relative risk appeared in the 40–50 age group (IRR 6.0, 95% CI 5.2–7.0).
For an average 30-year-old living with either type of diabetes, life expectancy was shortened by 14.2 years (type 1) and 7.9 years (type 2) compared with peers without diabetes, with sudden cardiac death accounting for about 3.4 and 2.7 of those lost years, respectively.
“Sudden cardiac death is challenging to predict and prevent, but these findings underscore the importance of reducing cardiovascular risk with diabetes management,” Skjelbred said in a statement. He added that multiple factors likely drive the link, which may vary by age. Diabetes increases the risk of ischemic heart disease, a key mechanism, while diabetes-specific factors such as hypoglycemia and autonomic neuropathy may raise the likelihood of arrhythmias and sudden death.
In younger adults under 30, incidence rates per 100,000 person-years were 19 for type 1 diabetes, versus 2.2 in non-diabetic individuals. In the 40–50 age bracket, rates were 186 (type 1), 178 (type 2), and 30 (general population) per 100,000 person-years.
The higher relative risks in younger people likely reflect the relatively low baseline risk of sudden cardiac death in that group, which makes the impact of diabetes appear larger. In older adults, other age-related risk factors lessen the relative effect of diabetes.
By age 90 and older, annual incidence reached 4,098 per 100,000 person-years for type 1 diabetes, 2,784 for type 2 diabetes, and 2,548 for the general population.
An accompanying editorial by Yaxuan Gao and Hanno L. Tan, MD, PhD (University of Amsterdam), notes that preventing sudden cardiac death remains a major challenge despite advances in cardiovascular care, due to its unpredictability and high fatality rate. The study helps quantify how diabetes shortens life expectancy and how much sudden cardiac death contributes to that loss.
The editorial also suggests that hypoglycemia and insulin therapy may act as independent risk factors for sudden cardiac death. Within the SCD group, 37% of those with type 1 diabetes and 7.2% with type 2 diabetes had a history of hospital contacts for severe hypoglycemia, highlighting a potential link between insulin-related hypoglycemia and fatal outcomes.
Skjelbred and colleagues explain that while tighter glycemic control reduces cardiovascular events, it can increase the risk of hypoglycemia when using insulin or sulfonylureas. Acute hypoglycemia triggers sympathetic activation, raises cardiac workload, and is associated with QT prolongation and low potassium—factors that can promote dangerous heart rhythms. Hypoglycemia also provokes prolonged inflammatory and prothrombotic responses that might contribute to sudden death.
Determining whether hypoglycemia caused death in post-mortem cases is difficult, because glucose levels change rapidly after death. Therefore, it cannot be ruled out that hypoglycemia contributed to some autopsy-negative sudden cardiac deaths. The SCD cases also showed a high rate of prior hospitalization for severe hypoglycemia, and among type 2 diabetes patients with SCD, insulin use was common, suggesting a greater hypoglycemic burden in these cases.
The Danish cohort included all residents alive in 2010: 5.4 million without diabetes, 25,020 with type 1 diabetes, and 172,669 with type 2 diabetes. Sudden cardiac death cases were identified through death certificates, hospital records, and autopsy reports from the 54,028 deaths recorded in Denmark in 2010.
Of the 6,862 SCD cases, 97 were in people with type 1 diabetes, 1,149 in those with type 2 diabetes, and 5,616 in people without diabetes.
Those with diabetes tended to be older and more often male than the general population. They also had higher rates of cardiovascular conditions such as heart failure, ischemic heart disease, prior myocardial infarction, high cholesterol, hypertension, and peripheral artery disease, along with more non-cardiovascular comorbidities like chronic kidney disease, COPD, neurological disease, liver disease, and psychiatric illness.
A key limitation is that the study focused on deaths from 2010, before the widespread adoption of newer glucose-lowering therapies like SGLT2 inhibitors and GLP-1 receptor agonists. Consequently, it cannot assess how these newer treatments may have influenced sudden cardiac death in more recent years.
