This document summarizes a study estimating the global prevalence of prediabetes in 2021 and projecting it to 2045. The study found that in 2021, 9.1% of adults worldwide had impaired glucose tolerance (IGT) and 5.8% had impaired fasting glucose (IFG). By 2045, these numbers are projected to rise to 10.0% and 6.5%, respectively. The burden is expected to increase most sharply in low-income countries. The results underscore the need for effective diabetes prevention strategies, especially in resource-limited settings. However, the study was limited by differences in how prediabetes was defined and measured across locations.

1. Journal Club
DR. PRODIPTA CHOWDHURY
PHASE B RESIDENT
DEPARTMENT OF ENDOCRINOLOGY

2. Global Prevalence of Prediabetes
Rooney, M.R., Fang, M., Ogurtsova, K.,Ozkan, B., Echouffo-Tcheugui, J.B., Boyko, E.J., Magliano, D.J.
and Selvin, E., 2023. Global Prevalence of Prediabetes. Diabetes Care, p.dc222376

3. Objective
To estimate prevalence of prediabetes
Defined by
◦ Impaired glucose tolerance (IGT)
◦ or Impaired fasting glucose (IFG)
on
◦ global, regional, and national basis

4. Introduction
Prediabetes:
oCondition characterized by elevated blood glucose levels
oBelow the threshold for a diagnosis of diabetes
oBut associated with a higher risk of developing diabetes
Condition WHO ADA
Impaired glucose tolerance
(IGT)
2-h glucose 7.8–11.0 mol/L
[140–199 mg/dL]
Same
Impaired fasting glucose
(IFG)
Fasting glucose 6.1–6.9
mmol/L [110–125 mg/dL]
5.5–6.9 mmol/L or [100–
125 mg/dL]
HbA1C 42–46 mmol/mol
(6.0–6.4%)
39–46mmol/mol
(5.7–6.4%)

5. IGT : Insulin resistance in muscle and decreased glucose uptake
IFG : Insulin resistance in the liver and excess hepatic glucose production
Limited overlap between IGT and IFG
20–25% of people with IGT have IFG
30–45% of individuals with IFG have IGT
High risk for developing diabetes, with up to 50% progressing to diabetes within 5 years

6. Pre-diabetic people are elevated risk of
◦ Chronic kidney disease
◦ Cardiovascular disease
◦ Mortality
To reduce the risk of progression to diabetes
◦ Intensive lifestyle intervention (e.g. dietary modification and increased physical activity)
◦ Pharmacological intervention (e.g. metformin)

7. Research design & Method
Literature Search
IDF methods to systematically select and analyze studies from the peer-reviewed and gray
literature
PubMed, Medline, and Google Scholar in November 2020 for publications
Use them to generate the 2021 prevalence estimates for IGT and IFG in IDF Diabetes Atlas,
10th edition

8. In addition to peer reviewed publications
National estimates from the gray literature
WHO STEP wise approach for NCD
Contacted ministries of health and all IDF regional partners for unpublished data related to IFG
and IGT
Only prediabetes prevalence after 2005 were included in the estimation, except for countries
whose only data predated 2005.

9. First screened by two
independent reviewers
for potential relevance
The full text was
reviewed by two
independent reviewers
Conflicts were resolved
by a third reviewer

10. Inclusion Criteria Exclusion Criteria
• Prediabetes - prevalence and/or number of
people
• Population based studies in adults (national
or regional)
• Registries and insurance-based data
• English language studies & non-English
language studies via the IDF network
• Impaired glucose tolerance (IGT)
• Impaired fasting glucose (IFG)
• Hemoglobin A1C (HbA1C)
• Diabetes prevalence only (i.e. no prediabetes)
• Prediabetes in specific populations
(occupational) e.g. nurses, taxi drivers
• Prediabetes in specific diseases, e.g. in people
with cardiovascular disease, kidney disease
• Prediabetes in specific age groups, e.g.
children, adolescents, elderly, 65+ years
• Hospital- or clinic-based studies or general
practice studies
• Studies in children and adolescents
• Type 1 diabetes
• Family studies, birth cohorts

11. Scoring the Quality of the Data
Scored for quality using the Analytical Hierarchy Process
According to national representativeness, diagnostic criteria, sample size, year of data source,
etc
Studies that met the 0.29 threshold for high-quality data were included
When more than one study met the threshold, study estimates were weighted for sample size

12. Estimating the Prevalence of IGT & IFG in
2021 & 2045
Based on WHO definitions of IFG and IGT
Separate logistic regression models to produce smoothed prevalence estimates of IGT and IFG
Models included adjustment for age, using age distribution for each country in 2021 from the
United Nations criteria
Models were run stratified by sex (male or female), setting (urban or rural), and age (adults
aged 20–79 years, 5-year increments) category–specific estimates

13. Countries without high-quality in-country data
◦ Methods used that were established by the IDF to extrapolate prevalence estimates
◦ From countries deemed to be similar based on geography, IDF region, ethnicity, language, and World
Bank income classification
Studies that did not report results stratified by urbanization, urban and rural ratios were
calculated according to the weighted average of the ratios reported in various data sources from
the seven IDF regions and the four World Bank income classifications.

14. Confidence interval for each IGT and IFG prevalence estimate separately for each country using
a process that included
1) A simulation analysis to estimate uncertainty for each study &
2) A jackknife analysis to estimate uncertainty due to study inclusion

15. Future projections were calculated using the United Nations population predictions
Projections of IGT and IFG prevalence estimates in 2045 using data from the United Nations on
midyear population projections
Analyses were performed using R software version 4.0.3
Graphics were generated using Microsoft Excel

16. Results
Literature review : 7,014 articles
Of the 215 world countries and territories
43 countries (20.0%) had high-quality data sources for estimating IGT
40 countries (18.6%) had high-quality data sources for estimating IFG
11 countries (4.8%) had estimates for both IGT and IFG
40% of the world population was represented in IGT data sources
18% was represented in studies of IFG

17. Countries with data sources for IGT
and/or for IFG

18. Prevalence for IGT and IFG in adults globally
and by IDF region

19. Prevalence for IGT in adults globally and
by IDF region
Rank 2021 2045
IGT IDF region Prevalence, % No. of people
with condition,
millions
Prevalence, % No. of people
with condition,
millions
World 9.1 464 10.0 638
1 North America & Caribbean 13.1 47 13.8 57
2 South and Central America 11.6 40 12.8 53
3 Western Pacific 11.1 193 11.8 213
4 Middle East and North Africa 10.6 48 11.5 81
5 Africa 9.7 51 11.1 117
6 Europe 5.9 39 6.2 41
7 Southeast Asia 4.5 47 5.7 77

20. Prevalence for IFG in adults globally and
by IDF region
Rank 2021 2045
IGT IDF region Prevalence, % No. of people
with condition,
millions
Prevalence, % No. of people
with condition,
millions
World 5.8 298 6.5 414
1 Southeast Asia 9.4 97 9.6 128
2 Middle East and North Africa 7.9 35 8.5 60
3 North America & Caribbean 7.6 28 8 33
4 Africa 5.7 30 6.3 67
5 South and Central America 5 17 5.6 23
6 Europe 4.8 32 5.2 34
7 Western Pacific 3.4 60 3.8 69

21. Prevalence of IGT and IFG in adults aged
20–79 years globally and by World Bank
income classification

22. Projected 130% increase in the number of people in low-income countries with IGT from 2021
to 2045 versus
• 38% in middle-income and
• 8% in high-income countries
For IFG, there will be a projected 122% increase in the number of people with IFG from 2021 to
2045 versus
• 41% in middle-income countries and
• 6% in high-income countries

23. Prevalence of IGT in adults aged 20–79
years in 2021 and 2045 by age group

24. Prevalence of IFG in adults aged 20–79
years in 2021 and 2045 by age group

25. Prevalence of IGT in adults aged 20-79
years in 2021 and 2045, by sex

26. Prevalence of IFG in adults aged 20-79
years in 2021 and 2045, by sex

27. Prevalence of IGT in adults aged 20-79
years in 2021 and 2045, by setting

28. Prevalence of IFG in adults aged 20-79
years in 2021 and 2045, by setting

29. Conclusions
Atlas 9 estimated the age-adjusted global prevalence of pre-diabetes to be 8.6% , compared
with 9.1% in these analyses.
This difference indicates a small increase in the global prevalence of IGT from 2019 to 2021.
The growing burden of prediabetes underscores the importance of effectively implementing
diabetes prevention policies and interventions.
Diabetes Prevention Program was established in high and middle income countries in 2010 to
slow the progression from prediabetes to diabetes at the population level.

30. Lower-income countries are less likely to have the resources, personnel, and public health and
health care infrastructure needed to implement and maintain these efforts at a national level.
There is an urgent need for effective strategies that can prevent diabetes progression in low-
income settings, such as community-based and group-based lifestyle interventions.

31. Changes in public health policy (e.g. regulation of food marketing and taxation) and educational
campaigns (e.g. transparency in food labeling) can be initiated without adding extra burden to
the existing health care infrastructure.
This is particularly important because these countries are expected to have the largest relative
growth in prediabetes prevalence over the next 25 years.

32. Consistent with prior research, these analyses found that the prevalence of IGT was higher in
urban (vs. rural) settings.
The adoption of sedentary behaviors and “Western” dietary patterns may explain the link
between urbanization and worse cardiometabolic health.

33. Currently global data on prediabetes in the literature is poor
This study provided the first global estimates of IFG based on high-quality information for 40
countries.
Overall, only about one-third of all countries had high quality data for IFG or IGT.
This highlights the need for improvements in population surveillance for prediabetes, especially in
low-income settings, where few data were available.
Continuing and expanding global surveillance efforts, such as the WHO STEPS surveys, can help to
provide data to fill this gap.

34. Limitations
This systematic review reflect those of the existing literature on prediabetes.
First, the studies included in these analyses had considerable differences in population,
sampling methodology, and date or period of data collection.
This heterogenicity is sought to reduce by analyzing contemporary, high-quality studies.
Nonetheless, these methodological differences likely influenced the comparability of estimates
across countries.

35. Second, only two definitions of prediabetes (IGT and IFG based on the WHO criteria) were examined.
Currently, there is no consensus definition of prediabetes.
There are at least five different definitions endorsed by different professional organizations and
guidelines based on fasting glucose, 2-h glucose, or HbA1c
They also did not estimate the prevalence of prediabetes defined by HbA1c due to the limited
availability of HbA1c assay in low income settings & lack of prediabetes definition by HbA1c in the
international scientific literature.

36. Broadening the use of HbA1c testing may be useful for improving global surveillance efforts on
prediabetes,
As HbA1c is a non–fasting test (no participant preparation is required) and can be convenient for
large-scale surveys and thus population surveillance

37. Third, authors considered the prevalence of IGT and IFG separately, as studies rarely had both
measures available; however, the overlap between the IFG and IGT populations may be limited.
Fourth, projections to 2045 are based on projected demographic changes in age and sex
distribution and the urban-to-rural ratio and did not factor in changes in other important
determinants of prediabetes, e.g. changes in BMI.

38. Fifth, extrapolation approach for missing data was informed by expert consensus but has not
been formally validated.
Nonetheless, extensive extrapolation for sparse or missing data are required for generating
global estimates for any health condition.
Lastly, publications that were published after initial search for the IDF Diabetes Atlas, 10th
edition, were not considered.

39. Take Home Message
 This article determined the global prevalence of impaired glucose tolerance (IGT) or impaired
fasting glucose (IFG) in adults aged 20–79 years.
 In 2021, 9.1% (464 million) of adults worldwide had IGT and 5.8% (298 million) had IFG.
 The burden of IGT and IFG is projected to increase significantly over the next two decades.
 Effective diabetes prevention policies and interventions are urgently needed.

42. Thank You