Introduction (original) (raw)

A proud history of information dissemination and advocacy

Since its first edition, published in 2000, the IDF Diabetes Atlas has provided robust estimates of the prevalence of diabetes by country, IDF Region and globally. Since its second edition, published in 2003, it has also projected these estimates into the future. In doing so, it has served as an advocacy tool, not only for the quantification of the impact of diabetes worldwide, but also for reducing that impact through measures aimed at improving the long-term consequences of all types of diabetes, as well as the primary prevention of type 2 diabetes.

In 2000, the global estimate of diabetes prevalence in the 20–79 year-old age group was 151 million, close to the WHO estimate at the time (150 million).1 The most recent WHO estimate (2014) of 422 million people with diabetes was also very close to the IDF estimate of 415 million people with diabetes in 2015. Since then, IDF estimates have indicated alarming increases in the number of people living with diabetes (see Figure 1), more than tripling the 2000 figure to the current (2021) estimate of 537 million.

Figure 1

Estimates and projections of the global prevalence of diabetes in the 20–79 year age group in millions (IDF Diabetes Atlas editions 1st to 10th).

For the first time, we are able to present the impact of type 1 and type 2 diabetes in different stages of life

Our vision for the IDF Diabetes Atlas 10th edition

The 10th edition of the IDF Diabetes Atlas has two inter-related objectives:

• ■ Advocacy for the continued and more effective use of the IDF Diabetes Atlas and its further improvement.
• ■ Innovation and continued development for the 10th edition including the utilisation of new methods and incorporation of new data sources.

Multiple changes have been made to the epidemiological methods used in preparing the 10th edition of the IDF Diabetes Atlas. These are summarised in Chapter 2 and are described in detail in a separate publication by Sun et al.2 New data have been accessed and some topics have been introduced for the first time (see ‘What’s new in the 10th edition?’ below). However, the basis on which estimates and projections have been calculated in this edition remain essentially the same as those used in the previous edition. Thus, continuity has been maintained and, with certain caveats, conclusions about time trends in the global progress of diabetes can be made with reasonable confidence.

What’s new in the 10th edition?

This year we have included a chapter on COVID-19 infection and diabetes which examines how diabetes influences not only the risk of contracting COVID-19 infection, but also what effects diabetes has on the clinical course of infection, including the need for hospitalisation, ICU care, and mortality (Chapter 4).

For the first time, we are able to present type 1 and type 2 diabetes prevalence in different stages of life. The worrying emergence of type 2 diabetes in children and adolescents has been recognised and is included alongside type 1 diabetes in these age groups (Chapter 3). The number of adults over 20 living with type 1 diabetes has also been presented (Chapter 3).

In each edition of the Atlas, we estimate diabetes prevalence based on the best quality data available at the time of analysis

Increased recognition of pre-diabetes has allowed us to report recent data on its prevalence (Chapter 3).

Estimates of the incidence of diabetes are included, recognising that, given many people with diabetes are living longer, influences on prevalence are complex and the global impact of diabetes is best assessed using incidence as well as prevalence (Chapter 3).

The importance of the advocacy objective of the IDF Diabetes Atlas and related materials is given attention. For that purpose, a separate 10 Steps to Data-driven advocacy is also available, serving as a stimulus to the use of the IDF Diabetes Atlas data for advocacy purposes to a broader audience.

How to read this edition of the IDF Diabetes Atlas

Although it might be tempting to focus solely on the figures for a given country or IDF Region, other factors should be considered when interpreting the IDF Diabetes Atlas estimates and any differences from those given in the previous edition. Possible reasons to account for significant differences between the 9th (2019) and 10th edition (2021) figures are:

• ■ The inclusion of new studies for some countries with in-country data sources in the previous edition.†
• ■ The inclusion of national diabetes registry data with modification. Data on diagnosed diabetes from these sources were adjusted to include both diagnosed and an estimate of undiagnosed diabetes.
• ■ The exclusion of specific WHO STEPS surveys included in the previous edition, as a result of concerns about their validity (see Chapter 2).
• ■ While we may include several studies for one country which all met inclusion criteria, in cases where multiple serial surveys were available, only the latest survey was included.
• ■ The exclusion of studies conducted before 2005, with the exception of cases when no other data source is available. Since older studies probably report a lower prevalence, the exclusion of these studies may result in an estimate of prevalence being higher than previous editions.
• ■ Likewise, updating data sources with better quality studies may result in a lower prevalence than reports from previous years with less robust methodology. Any change in prevalence within individual countries could be due, in part, to these methodological changes.

It must be stressed that any differences between the 9th and 10th edition estimates may be due to updating of studies, rather than to real changes in diabetes prevalence since the 9th edition in 2019. For example, the 2019 estimate for a country might have been based on a study conducted in 2005, but the 2021 estimate was able to include a study published in 2020.

In each edition of the IDF Diabetes Atlas, we estimate diabetes prevalence based on the best quality data available at the time of analysis. It is important to highlight that the diabetes figures presented in this document are therefore estimates and thus changes in the magnitude of prevalence of individual countries from edition to edition should be treated with caution.

Limitations

• ■ The definition of diabetes used in the IDF Diabetes Atlas is based on an epidemiological definition which requires abnormal blood glucose levels to be detected on only one test compared to a clinical diagnosis of diabetes which requires abnormal blood glucose levels to be detected on two separate tests.
• ■ While we attempted to include only population-based representative studies, all studies have limitations and biases which require careful interpretation. In some countries/territories where territory-wide or population-based registers were included, the estimate of prevalence was adjusted, taking into consideration the proportion of people with undiagnosed diabetes in that country/territory.
• ■ When a country lacked any internal data, diabetes prevalence was extrapolated from a country with similar economy, language and demography. Such extrapolations may represent a source of error.
• ■ The urban and rural classifications are based on how the individual data sources defined urban and rural, rather than defined by the IDF analysis team.