Introduction
Population-based surveillance is essential for quantifying the burden of diabetes and monitoring temporal changes. In Denmark, nationwide health registers enable long-term surveillance of type 1 diabetes (T1D) and type 2 diabetes (T2D). We aimed to estimate trends in prevalence, incidence, mortality and years of life lost to diabetes in Denmark from 1996 to 2024.
Research design and methods
We conducted a nationwide register-based cohort study from 1996 to 2024. We used an updated national diabetes register integrating hospital, prescription, clinical, and laboratory data to identify diabetes type and date of onset. Prevalence was estimated annually using a binomial model. Incidence, mortality and standardized mortality ratios (SMR) were analyzed using age-period-cohort models. Analyses were stratified by sex and diabetes type. A multistate model was used to assess the lifetime risk and years of life lost to diabetes.
Results
As of January 1, 2025, a total of 366 174 individuals (6.1% of the population) had diabetes identified through national healthcare registers; of these, 8.2% had T1D and 91.8% had T2D. Since 1996, diabetes prevalence more than tripled, largely driven by an overall annual increase in T2D of ~4.1%. T1D prevalence remained stable, with increases in individuals aged <40 years and decreases in older age groups. From 1996 to 2024, a total of 567 510 incident diabetes cases were recorded, of which 4.6% were T1D. T1D incidence declined on average by 1.1% annually, with increasing rates at younger ages and declining rates at older ages. T2D incidence showed a non-linear pattern, with a decline from 2010 to 2015 followed by an increase in recent years, resulting in an overall upward trend from 1996 to 2024. Men had higher T2D incidence than women across age and calendar years. Mortality declined for T1D after 2008 and for T2D until 2012, then stabilized. SMRs decreased for T1D after 2008 but increased for T2D, converging by 2025.
Conclusions
In Denmark, diabetes prevalence and incidence increased markedly since 1996, largely driven by T2D. Although mortality declined, particularly for T1D, excess mortality remains, emphasizing the need for continued surveillance and prevention efforts.
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