Temporal changes in the prevalence of diagnosed diabetes, undiagnosed diabetes and prediabetes: findings from the German Health Interview and Examination Surveys in 1997-1999 and 2008-2011

Aims Nationally representative data on temporal changes in the prevalence of diagnosed diabetes, as well as undiagnosed diabetes and prediabetes, have been lacking in Germany as in most other European countries. We aimed to fill this gap using data from nationwide examination surveys of German adults. Methods The study population comprised 18–79‐year‐old participants from the German Health Interview and Examination Surveys in 1997–1999 (GNHIES98, n = 6655) and 2008–2011 (DEGS1, n = 7017). Participants were classified as having diagnosed diabetes based on self‐reported physician‐diagnosed diabetes or the use of anti‐diabetes agents. Among those without diagnosed diabetes, HbA1c measures were used to define undiagnosed diabetes [≥ 48 mmol/mol (≥ 6.5%)] or prediabetes [39–47 mmol/mol (5.7–6.4%)]. Results Although the age‐ and sex‐standardized prevalence of total diabetes remained stable between 1997–1999 at 9.3% (95% CI 8.3–10.5%) and 2008–2011 at 9.2% (8.3–10.3%), the prevalence of diagnosed diabetes increased from 5.6% (4.9–6.3%) to 7.2% (6.5–8.0%), whereas the prevalence of undiagnosed diabetes decreased from 3.8% (3.1–4.6%) to 2.0% (1.5–2.7%), resulting in a decreased proportion of undiagnosed diabetes (40.9% vs. 21.7%). Over the same period, the prevalence of prediabetes decreased from 27.7% (25.6–29.8%) to 20.8% (18.2–23.7%). Observed temporal changes were not explained by changes in BMI, sport activity and educational level. Conclusions The two nationwide surveys indicate a shift from undiagnosed to diagnosed diabetes. However, the unchanged prevalence of total diabetes and the considerably high proportion of prediabetes strongly call for a continued and concerted effort in diabetes prevention among German adults. What's new? For the first time, this study provides recent, nationally representative prevalence estimates and temporal changes for diagnosed diabetes, as well as for undiagnosed diabetes and prediabetes in Germany by combining interview, medication and laboratory data from health surveys. We observed opposing prevalence changes for diagnosed diabetes (that increased) and undiagnosed diabetes and prediabetes (that decreased) independent of changes in age structure, BMI, sport activity or education level over the last decade. The decreased proportion of diabetes that is undiagnosed suggests a better health system responsiveness regarding diabetes diagnosis and care. However, Germany continues to have one of the largest burdens of diabetes with