Monitoring diabetes trends is crucial for disease management and health policy. At a global level, however, the burden of type 2 diabetes is mainly monitored by evaluating prevalence data, which alone is not sufficient, as the incidence must also be taken into account when estimating risk trends in the population. Based on results from Bavaria, the development of type 2 diabetes incidence in the years 2012 to 2021 has now been examined in a secondary data analysis.
Diabetes mellitus places a heavy burden on the population and healthcare systems. Approximately 11% of the world’s population (537 million people) aged 20 to 79 years were living with diabetes (type 1 or type 2) in 2021. This number is expected to rise to 783 million by 2045.
There are only 12 diabetes registries worldwide, mainly in the northern part of Europe, with varying levels of registry quality. However, not all of them report HbA1c measurements, one of the most important values for blood glucose control. The incidence rates of type 2 diabetes are rarely published, while evaluations of the prevalence of diabetes are a standard measure for both types of diabetes. However, monitoring prevalence alone is not sufficient to capture the burden of disease and the impact of prevention programs, as life expectancy and survival of those diagnosed with diabetes determine prevalence alongside the incidence of new cases. Although the increasing prevalence of type 2 diabetes in Germany suggests an increase in the burden of disease, the incidence data should also be taken into account.
A team led by Prof. Dr. Stefanie Klug and first author Carolin T. Lehner from the Department of Epidemiology at the Faculty of Medicine and Health at the Technical University of Munich (D) investigated the temporal development of type 2 diabetes incidence in the largest German state of Bavaria from 2012 to 2021 [1]. Using routinely collected data on the health insurance claims of all those with statutory health insurance there, they compared the incidence rates in the pandemic period (2020-2021) with the period before the pandemic (2012-2019). The data from the Association of Statutory Health Insurance Physicians in Bavaria (KVB) covers outpatient care for the entire 11 million people with statutory health insurance, which corresponds to 85% of the regional population there.
Newly diagnosed cases of type 2 diabetes in adults (≥20 years) coded according to ICD-10, German modification (ICD-10-GM), as E11 (diabetes mellitus type 2) or E14 (unspecified diabetes mellitus) for the study period were included. Annual and quarterly age-standardized incidence rates (ASIR), stratified by sex, age and region, were calculated using the European standard population. Sex-specific crude incidence rates (CIR) were calculated using 10-year age groups. Regression analyses adjusted for time trends, seasonal effects and pandemic effects were used to analyze incidence trends and assess the impact of the pandemic.
Age-standardized incidence rates are declining
A total of 745,861 new cases of type 2 diabetes were diagnosed between 2012 and 2021; 50.4% (376,193 cases) in women and 49.6% (369,668 cases) in men. The average age at diagnosis throughout the study period was 62.66 years, with the age at diagnosis being higher for women (65.46 years) than for men (61.09 years). The ratio of men to women with type 2 diabetes remained stable during the observation period, while the mean age at diagnosis fell from 61.3 to 58.3 years (-3.0 years) for men and from 65.9 to 61.1 years (-4.8 years) for women.
The overall ASIR for type 2 diabetes was 1009 per 100,000 person-years from 2012 to 2021, with rates consistently higher in men than in women and the gender difference remaining stable during the study period (2012: 18% vs. 2021: 20%). Overall, a downward trend in ASIR was observed, with a sharp decline from 2012 to 2017, followed by a less pronounced decline from 2018 to 2021 (Fig. 1). For men, the ASIR decreased by 32.4% in the pre-pandemic period and by 34.3% over the entire study period; for women, these values were 34.9% and 35.7% respectively. This corresponds to an average annual decrease for men and women of 5.4% and 5.9% in the pre-pandemic period and 4.6% and 4.8% for the entire study period. The age-stratified incidence rates show the same downward trend for those over 50 years of age, while the younger age groups 20-29, 30-39 and 40-49 are stable for both genders. The CIR increased with age, with the highest CIR observed in the age group 60-69 years for men and 70-79 years for women. Regression analyses showed no significant change in incidence rates during the pandemic period (2020 and 2021) compared to the period before.
COVID-19 pandemic with no discernible impact
Type 2 diabetes usually affects slightly more men than women, but as the authors note, their study found an almost equal number of cases in men and women. While recent prevalence data shows that more men (41.3%) are overweight than women (27.6%), there is no gender difference in obesity prevalence in Germany.
The researchers highlight that the incidence rate has not changed during the COVID-19 pandemic period (2020-2021) compared to the pre-pandemic period. According to them, this suggests that the incidence of type 2 diabetes was not affected in the first two years of the pandemic.
According to their conclusions, the results would therefore indicate that patients continue to see their GPs (and to a lesser extent their specialists). However, type 2 diabetes often develops slowly over several years, so the direct impact of the pandemic on incidence may be reflected with a delay. For this reason, future monitoring is needed to assess the long-term impact of the pandemic on diabetes incidence.
Forecasts for Germany indicate that the prevalence of type 2 diabetes will increase by 54% to 77% (in people aged 18 and over) by 2040, with the trend in incidence being the most important factor in this increase. Rising prevalence can go hand in hand with falling incidence, the authors point out. By monitoring and evaluating both prevalence and incidence, a better understanding of the burden of type 2 diabetes can be achieved.
Take-Home-Messages
- The incidence of type 2 diabetes has decreased from 2012 to 2021, with a sharp decline from 2012 to 2017, followed by a less pronounced decline from 2018 to 2021.
- In the same overall period, the median age at diagnosis fell by 3.0 years for men and 4.8 years for women.
- The incidence rates of type 2 diabetes have not changed in the 2020-2021 pandemic period compared to the pre-pandemic period (2012-2019).
- By means of monitoring and reporting, both prevalence and incidence should be taken into account in diabetes management and health policy.
Literature:
- Lehner CT, Eberl M, Donnachie E, et al.: Incidence trend of type 2 diabetes from 2012 to 2021 in Germany: an analysis of health claims data of 11 million statutorily insured people. Diabetologia 2024; 67: 1040–1050; doi: 10.1007/s00125-024-06113-8.
InFo DIABETOLOGIE ENDOKRINOLOGIE 2024; 1(3): 38–39
