Diabetes and Sudden Cardiac Death

A comprehensive Danish nationwide study has revealed the substantial burden of sudden cardiac death (SCD) amongst individuals with diabetes, demonstrating significantly elevated incidence rates and considerable reductions in life expectancy attributable to cardiac events.

The study examined the entire Danish population of 5.5 million people throughout 2010, identifying 6,862 SCD cases. Amongst these, 97 individuals had Type 1 diabetes (T1D), and 1,149 had Type 2 diabetes (T2D). The research team manually reviewed all deaths using death certificates, discharge summaries, and autopsy reports to accurately classify sudden cardiac deaths, defined as sudden, natural, and unexpected deaths with underlying cardiac causes.

The study revealed significant disparities in SCD rates. Incidence rates of SCD were 3.7 times higher for T1D and 6.5 times higher for T2D compared with the general population. The overall incidence rates per 100,000 person-years were 394 for T1D and 681 for T2D, compared with just 105 in the background population.

The greatest risk difference was observed in younger individuals with diabetes. For those under 50 years, the hazard ratios were approximately seven-fold higher for both diabetes types. This relative risk decreased with age, falling to roughly 1.5-fold in those over 75 years. The higher ratios in younger individuals reflect the low background risk of SCD in this age group, making the relative impact of diabetes more pronounced.

The study also quantified the impact on life expectancy. Life-years lost were on average 14.2 and 7.9 years shorter for patients with T1D and T2D, respectively. A reduced life expectancy of 3.4 and 2.7 years was found to be attributed to SCD for T1D and T2D, respectively. These findings demonstrate that SCD represents a major contributor to premature mortality in diabetes.

Individuals with diabetes who experienced SCD differed markedly from the general population. T1D patients averaged 45 years of age, while T2D patients averaged 64 years, both significantly older than the general population average of 37 years. Male sex was more prevalent amongst diabetes patients. The SCD cases with diabetes were younger than non-diabetic SCD cases, with an average age difference of 14.2 years for T1D patients.

Comorbidities were more common in diabetic populations, including higher rates of heart failure, ischaemic heart disease, atrial fibrillation, and chronic kidney disease. Amongst SCD cases with diabetes, 37% of T1D patients and 7.2% of T2D patients had previous hospital contact for hypoglycaemia, suggesting this complication may play an important role in SCD risk.

The researchers identified several potential pathways linking diabetes to SCD. Beyond the connection through ischaemic heart disease, they highlighted cardiac autonomic neuropathy. Hypoglycaemia was also a concerning factor.

The study found that SCD incidence rates were highest amongst individuals treated with insulin, intermediate amongst those using combined insulin and oral medications, and lowest amongst those on oral medications alone. This pattern suggests a possible link between hypoglycaemic risk and SCD vulnerability.

These findings highlight the need for improved SCD prevention strategies in diabetic populations. Current prevention focuses primarily on high-risk patients with known cardiovascular disease, potentially overlooking vulnerable diabetic individuals. The researchers suggest that newer cardioprotective medications, such as sodium-glucose cotransporter-2 inhibitors and glucagon-like peptide-1 agonists, may offer promise, though their specific effects on ventricular arrhythmias require further investigation.

Overall, diabetes substantially increases SCD risk across all age groups, with the greatest relative impact in younger individuals. The considerable proportion of reduced life expectancy attributable to SCD in both T1D and T2D populations highlights the importance of understanding diabetes-specific mechanisms contributing to ventricular arrhythmias and developing targeted prevention strategies for this high-risk population.

Source: European Heart Journal

Image Credit: European Heart Journal