The global diabetes burden has been increasing due to the higher prevalence and incidence of diabetes over the past 28 years.¹ However, the severity in diabetes burden differs by country, region, ethnicity, and diabetes type.^1,2 Thus, there is an inconsistency in the studied trends in diabetes incidence, as some populations have had a decrease in incidence since 2006.³ In Trends in the incidence of diagnosed diabetes: a multicountry analysis of aggregate data from 22 million diagnoses in high-income and middle-income settings, the authors addressed this gap by acquiring diabetes incidence data from 21 countries. They incorporated nationally representative data sources on diagnosed diabetes, using both a standardized data collection tool and a prespecified protocol.⁴

Magliano et al. used incidence as a basis for analyzing diagnosed diabetes rather than prevalence. The authors gathered aggregate data from administrative sources, health insurance records, registries, and health surveys across 21 countries. Nineteen of the countries were classified as high-income countries and the other two were middle-income countries. The time period of analysis was from 1995 to 2018. Diabetes was defined differently among the data sources: ten of the data sources used clinical diagnosis, another ten used an algorithm, three used diabetes medication, and one used self-report of a health-care provider. Nineteen countries had a declining incidence trend from 2010 with a yearly rate change of -1.1% to -10.8%, while four countries (Israel [Maccabi Healthcare Services], Lithuania, Singapore, and the United States [US] [Kaiser Permanente Northwest]) had an increasing incidence trend from 2010 with a yearly rate change of 0.9% to 5.6%.⁴ Magliano et al. attribute the declining diabetes incidence to global preventive strategies of type 2 diabetes, including educational campaigns, lifestyle changes for those at high risk of type 2 diabetes, promotion of physical activity, and increased taxes on certain foods and drinks.⁴ However, the source they included focused only on the decrease in purchases of unhealthy food and beverages in the US, not globally. Next, the authors analyzed the implementation of HbA1c, a more sensitive diagnostic tool for diabetes, and changes in population screening for diabetes to account for the trends in incidence they found. However, there was no correlation between utilization of HbA1c in clinical practice or population screening, and changes in diabetes incidence. Lastly, they considered the threshold of fasting plasma glucose being lowered to 7.0 mmol/L in 1997 as an explanation for their results. Yet, the authors dismissed this reason because the decline in incidence was observed 15 years after this threshold was lowered.

This paper was innovative since the authors looked at trends across multiple countries and used nationally representative data sources. However, the authors did not discuss how they categorized countries into high-income and middle-income categories. Low-income countries were also not studied, which would have provided a more robust view of diabetes trends worldwide. Furthermore, rates of diagnosed versus undiagnosed diabetes vary among countries. Based on results from the International Diabetes Federation Diabetes Atlas, of the 463 million people living with diabetes worldwide, half (50.1%) are unaware of their condition.⁵ Additionally, higher proportions of undiagnosed diabetes were found in low- and middle-income countries, accounting for 84.3% of all undiagnosed people with diabetes worldwide.⁵ Therefore, the data taken from middle-income countries was not as representative of the true diabetes burden, compared to high-income countries where the numbers of diagnosed diabetes are more representative of the population as a whole.

Moreover, different types of data were analyzed for the countries that were studied. For example, Australia had a registry, whereas Canada had administrative data, and South Korea had health insurance data. Other countries, such as the US, had two or more types of the above-stated data that were analyzed. Therefore, the trends for some countries might be more scientifically-sound compared to others, especially since the definition of diabetes also varied among countries. The types of diabetes studied also differed by country, with most databases looking at all types of diabetes, and some countries solely looking at type 2. The authors then analyzed this data together, without differentiating between type 1 and type 2 diabetes trends. Later in the paper, the authors explained that one of the reasons there has been a decline in diabetes incidence might be due to preventive strategies, such as physical exercise, and reduction in drinking sugar-sweetened beverages. However, these preventive strategies specifically target type 2 diabetes, so it would have been more beneficial to distinguish diabetes trends between the two types. The authors also discussed findings from the US, which included reductions in drinking sugar-sweetened beverages and decreases in unhealthy food purchases. They then stated that these findings may have led to behavioral and environmental changes that affected the incidence of diagnosed diabetes globally. While this might be the case in the US, the authors did not provide additional evidence that supports this finding in the rest of the countries studied.

Although the results from this study are promising for many countries, there needs to be more exploration of the reasons behind the observed trends in diabetes incidence and why there may be increases in some countries and decreases in others. Furthermore, risk factors, such as BMI and abdominal obesity, are important considerations when discussing the epidemiology of diabetes.⁶ Most importantly, diabetes is increasing most rapidly in many low-income and middle-income countries, which carry approximately 75% of the global diabetes burden.⁷ Thus, these countries need to be included in future studies to establish high-quality, sustainable preventive strategies and care for diabetes.

References

1. Lin X, Xu Y, Pan X, et al. Global, regional, and national burden and trend of diabetes in 195 countries and territories: an analysis from 1990 to 2025. Sci Rep 2020;10:14790.
2. Liu J, Ren ZH, Qiang H, et al. Trends in the incidence of diabetes mellitus: results from the Global Burden of Disease Study 2017 and implications for diabetes mellitus prevention. BMC Public Health 2020;20:1415.
3. Magliano DJ, Islam RM, Barr ELM, et al. Trends in incidence of total or type 2 diabetes: systematic review. BMJ 2019;366:15003.
4. Magliano DJ, Chen L, Islam RM, et al. Trends in the incidence of diagnosed diabetes: a multicountry analysis of aggregate data from 22 million diagnoses in high-income and middle-income settings. Lancet Diabetes Endocrinol 2021;9:203-11.
5. Saeedi P, Petersohn I, Salpea P, et al. Global and regional diabetes prevalence estimates for 2019 and projections for 2030 and 2045: results from the International Diabetes Federation Diabetes Atlas, 9th edition. Diabetes Res Clin Pract 2019;157:107843.
6. Haghighatdoost F, Amini M, Feizi A, Iraj B. Are body mass index and waist circumference significant predictors of diabetes and prediabetes risk: results from a population-based cohort study. World J Diabetes 2017;8:365-73.
7. Manne-Goehler J, Geldsetzer P, Agoudavi K, et al. Health system performance for people with diabetes in 28 low- and middle-income countries: a cross-sectional study of nationally representative surveys. PLoS Med 2019;16:e1002751.

Clinical Topics: Cardiovascular Care Team, Diabetes and Cardiometabolic Disease, Prevention, Exercise

Keywords: Blood Glucose, Glycated Hemoglobin A, Self Report, Incidence, Diabetes Mellitus, Type 2, Prevalence, Obesity, Abdominal, Ethnic Groups, Developed Countries, Body Mass Index, Exercise, Risk Factors, Insurance, Health, Registries, Delivery of Health Care, Health Surveys, Life Style

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