HbA1c-defined prediabetes and progression to type 2 diabetes in Denmark: A population-based study based on routine clinical care laboratory data

Aims: To estimate the prevalence, incidence, mortality, and risk of progression to type 2 diabetes for individuals with HbA1c-defined prediabetes based on Danish nationwide population-based laboratory databases.Methods: We included all HbA1c measurements from general practice and hospitals during 2012 to 2018. We estimated the cumulative incidence of having at least one HbA1c measurement. The prevalence and incidence rates of prediabetes (HbA1c 42-47 mmol/mol) were examined in the adult Danish population. The 5-year cumulative incidence of progression to type 2 diabetes was estimated with death as competing event.Results: Among 4,979,590 adult Danes, 70.8% (95% CI 70.8-70.9) had at least one HbA1c measurement during 2012 to 2018. The prevalence of prediabetes was 7.1% (95% CI 7.1-7.1) in 2018. The incidence rate was 14.2 (95% CI 14.1-14.3) per 1,000 person-years, with median age 66.9 years (IQR 56.7-75.7) and median HbA1c 43 mmol/mol (IQR 42-44) at prediabetes diagnosis. Within five years, 17.5% (95% CI 17.3-17.7) died and the 5 year cumulative incidence of type 2 diabetes was 21.3% (95% CI 21.1-21.5).Conclusions: Out of 100 Danish adults, 1.4 develop prediabetes each year and they can be identified at an early stage in laboratory databases. Within five years, one in five individuals with prediabetes progresses to diabetes and one in six dies.