A Danish nationwide study shows that people with type 1 and type 2 diabetes face much higher rates of sudden cardiac death and lose years of life as a result, highlighting the urgent need to identify and protect those at greatest cardiac risk.
Study: Diabetes and sudden cardiac death: a Danish nationwide study. Image Credit: Yurchanka Siarhei / Shutterstock
A recent study published in the journal European Heart Journal estimated the incidence of sudden cardiac death (SCD) in people with Type 1 (T1D) and Type 2 diabetes (T2D), and quantified the life expectancy lost due to SCD.
Elevated Sudden Cardiac Death Risk in Diabetes
SCD is the unexpected death of a person caused by the sudden loss of heart function, which could be due to a cardiac electrical imbalance. Previous studies have shown that individuals without known cardiac disease represent the largest subgroup of SCD cases.
Current strategies to prevent SCD primarily target patients with existing cardiovascular disease, often overlooking vulnerable groups like those with diabetes. While people with diabetes are at increased risk for SCD, the true impact in this population is still unclear.
Individuals with diabetes live significantly shorter lives than the general population, with 30-year-olds losing about 14.2 years for T1D and 7.9 years for T2D. They also face fatal and nonfatal cardiovascular events earlier in life. Most of this reduced life expectancy is linked to cardiovascular disease, with SCD specifically accounting for 3.4 years lost in T1D and 2.7 years in T2D.
Nationwide Cohort to Measure SCD Burden
The current nationwide cohort study included all living people in Denmark from January 1 to December 31, 2010. For those who died, detailed information was collected from death certificates, discharge summaries, and, when available, autopsy reports. All potential sudden deaths underwent independent review by two physicians, with consensus resolution for disagreements. One physician manually reviewed all deaths to exclude cases that were clearly non-sudden or unnatural.
Population data were obtained from the Civil Registration Register using January 1, 2010, as the reference date. Individuals with diabetes were identified by cross-linking the Civil Registration Register with the Danish National Patient Register and the Register of Pharmaceutical Sales. For T1D, the identification method had a sensitivity of 0.70 and a specificity of 0.99. For T2D, the sensitivity was 0.91, and the specificity was 0.99.
As of January 1, 2010, Denmark had a population of 5.5 million. Throughout that year, there were 54,028 deaths in the country. Of these, 14.1% were classified as sudden death (SD), and 12.7% as SCD. A total of 25,020 individuals with T1D and 172,669 with T2D, with 97 and 1,149 SCD cases in each group, respectively. Patients with T1D and T2D were significantly older than the general population, with median ages of 45 and 64 years, respectively, compared with 37 years in the general population. Additionally, the proportion of males was higher among both T1D and T2D patients compared to the background population.
Diabetes Strongly Linked to Higher SCD Rates
Clinical data showed that SCD cases with diabetes were younger than non diabetic SCD cases and more often male. People with T1D and T2D had more cardiovascular comorbidities than those without diabetes. They had higher rates of ischaemic heart disease, heart failure, arrhythmia, and cardiomyopathy. In addition, these patients were also more likely to have kidney, lung, nerve, liver, and mental health issues. The researchers noted that these higher comorbidity rates may partly reflect more frequent healthcare contact among people with diabetes, thereby increasing the likelihood of detection. People with T2D exhibited a higher prevalence of ischaemic heart disease and myocardial infarction compared with those with T1D. SCD cases with T1D or T2D exhibited higher rates of cardiovascular as well as non-cardiovascular comorbidities. Many SCD cases with diabetes had a history of hospital admission due to diabetes related issues, with 37% of T1D-SCD and 7.2% of T2D-SCD cases having prior hypoglycemia hospitalizations.
The overall incidence rates (IRs) of SCD per 100,000 person-years are 394 for people with T1D and 681 for those with T2D. In comparison, the IR of SCD in the general population is 105. The difference in SCD rates between people with diabetes and those without is greatest in younger age groups. While absolute rates were higher in T2D, the relative risk was greatest in young T1D patients (22.7× higher in 30–40-year-olds). It must be noted that the incidence rate ratios (IRRs) decreased with increasing age.
From age 30 onwards, the probabilities of survival and death from SCD, non-SCD, and other causes were measured for people with T1D, T2D, and the general population. A 30-year-old with T1D was expected to live 14.2 years less than someone in the general population, with 3.4 of those years attributed to SCD. Similarly, a 30-year-old with T2D had a life expectancy 7.9 years shorter, with 2.7 years lost to SCD. The gap in life expectancy shrinks as people get older.
Researchers used Cox proportional hazards models to examine the association between diabetes and SCD, controlling for age as the underlying time scale. To assess whether the results were reliable, they divided ages into three groups: 0–50, 50–75, and 75+. Three Cox proportional hazards models were fitted with varying levels of adjustment, showing that diabetes remained an independent risk factor even after accounting for comorbidities such as heart disease and kidney failure.
Study Confirms Major Life Years Lost From SCD
The current nationwide study found that people with T1D and T2D are at a higher risk of SCD than the general population, i.e., 3.7 times higher for T1D and 6.5 times higher for T2D. This increased risk is especially noticeable in younger age groups, with the highest relative risk in young T1D patients.
Furthermore, people with diabetes also have a shorter life expectancy, with SCD accounting for a quantifiable portion (3.4 years in T1D, 2.7 years in T2D) of the years lost. The study also notes hypoglycemia as a potential contributor to SCD risk. In the future, more research is required to investigate why people with diabetes are at greater risk of SCD.
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