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We estimated the number of people worldwide with diabetes for the years 2010 and 2030.
Methods
Studies from 91 countries were used to calculate age- and sex-specific diabetes prevalences, which were applied to national population estimates, to determine national diabetes prevalences for all 216 countries for 2010 and 2030. Studies were identified using Medline, and contact with all national and regional International Diabetes Federation offices. Studies were included if diabetes prevalence was assessed using a population-based methodology, and was based on World Health Organization or American Diabetes Association diagnostic criteria for at least three separate age-groups within the 20–79 year range. Self-report or registry data were used if blood glucose assessment was not available.
Results
The world prevalence of diabetes among adults (aged 20–79 years) will be 6.4%, affecting 285 million adults, in 2010, and will increase to 7.7%, and 439 million adults by 2030. Between 2010 and 2030, there will be a 69% increase in numbers of adults with diabetes in developing countries and a 20% increase in developed countries.
Conclusion
These predictions, based on a larger number of studies than previous estimates, indicate a growing burden of diabetes, particularly in developing countries.
Diabetes mellitus is one of the most common chronic diseases in nearly all countries, and continues to increase in numbers and significance, as changing lifestyles lead to reduced physical activity, and increased obesity. Estimates of the current and future burden of diabetes are important in order to allocate community and health resources, and to emphasise the role of lifestyle, and encourage measures to counteract trends for increasing prevalence.
There have been several previous estimates of the number of persons with diabetes [
]. The World Health Organization (WHO) published estimates for the years 2000 and 2030, using data from 40 countries but extrapolated to the 191 WHO member states [
]. The estimates produced here update the previous IDF estimates, and include all 216 countries of the United Nations.
2. Materials and methods
2.1 Study selection
The Medline database was searched for publications between January 1989 and March 2009, using the following search term “Diabetes Mellitus/epidemiology” MeSH AND “Prevalence” MeSH. Studies were identified that reported on the prevalence of diabetes for at least three adult age-groups from a population-based sample. A number of other avenues were explored in the search for relevant data. Relevant citations from each article were obtained, and diabetes researchers in each major IDF geographical region, and IDF member associations in each member country were asked about relevant data. Studies were included if they assessed diabetes prevalence for a defined adult population-based sample, using WHO or American Diabetes Association (ADA) diagnostic criteria [
World Health Organization, Definition, diagnosis and classification of diabetes mellitus and its complications. Part 1: diagnosis and classification of diabetes mellitus. Department of Noncommunicable Disease Surveillance, Geneva, 1999. Report No.: WHO/NCD/NCS/99.2.
], with age-specific prevalences indicated for at least three distinct age-groups within the 20–79 year range. Self-report data, or registry data were used if blood glucose assessment was not available. The final selection of a study or studies for each country was determined by the study size, response rate, diagnostic criteria used (with preference for the oral glucose tolerance test) and by assessing the degree to which studies reflected the national population. The final selection included 133 studies from 91 countries. For those countries that did not have their own suitable study, a study (or studies) from another country were used, with selection of that study on the basis of the ethnic and socio-economic similarity of the population, as well as geographical proximity. National member associations of the IDF assisted with choice of which other country to use. Estimates were based on the total diabetes population, including those newly diagnosed on blood glucose testing by surveys, and those with type 1 diabetes.
2.2 Statistical methods
Prevalence estimates were derived for adults aged 20–79 years. Smoothed age-specific (5 year intervals) and sex-specific prevalence estimates were generated by applying logistic regression models using SPSS Version 15.0 (SPSS, Chicago, IL) to the available data, including a quadratic term to allow flattening for older ages. The age-specific data were centred on the mid-point of each age-group, and weighted by the number of cases with and without diabetes. Open-ended age-groups (such as 65+) were treated as if the open age-group were of the same size as the highest inclusive group (e.g. 55–64).
The smoothed age- and sex-specific prevalences were then applied to each national population distribution for the years 2010 and 2030 (United Nations Population estimates [
]) to estimate national prevalence and numbers of adults with diabetes. The age-specific prevalences of each country were also applied to the world population distribution to determine age- and sex-adjusted prevalences for each country. For countries designated as developing, by the UN classification [
] (i.e. all countries outside Europe, except Australia, Canada, Japan, New Zealand, USA, Singapore, Hong Kong and Taiwan), for which separate urban and rural prevalences were available, these were applied to the urban and rural components of the national adult population. For cases in which only urban or only rural data were available, urban prevalences were assumed to be twice those of rural, in keeping with previous assessments [
]. For the countries with multiple studies, data were combined. The same age- and sex-specific prevalence data were applied to 2010 and 2030, so that changes in national estimates were only affected by demographic (i.e. age, sex and urbanization) changes for each country.
Countries were assigned to regions based on the IDF membership regions (Africa; Eastern Mediterranean and Middle-East (EMME); Europe; North America; South and Central America (SACA); South Asia; Western Pacific).
For several of the studies (Canada, France, Italy, Netherlands, Norway, Slovenia, United Kingdom) data were only available on self-reported diabetes. To account for undiagnosed diabetes, the prevalences of diabetes for the United Kingdom and Canada were multiplied by a factor of 1.5, in accordance with local recommendation (UK) and data from the USA (Canada), and for the other countries doubled, based on data from a number of nearby countries.
3. Results
There were 133 studies identified from 91 countries. The data sources and the results for the 80 most populous countries (those with 2010 adult population of greater than 6.307 million, with a combined 2010 population of 95% of the world adult population) are shown in Table 1, Table 2. There were 47 of the 80 countries that had their own data (85 separate studies). Details of prevalence and case numbers for all 216 countries can be found in the online Appendix.
Table 1Studies identified for the largest 80 countries.
Country
Data used (country, year of publication, reference)
Prevalence of diabetes and impaired fasting glucose in the Chinese adult population: International Collaborative Study of Cardiovascular Disease in Asia (InterASIA).
Ministry of Health, Republic of Indonesia, National Basic Health Research 2007, Official Report (translated from RISKESDAS 2007, Sidartawan Soegondo), Jakarta, 2008.
Ministry of Health, Vietnam, Follow-up study on diabetic complications in patients since their first presentation at National Hospital of Endocrinology, TaVan Binh (Ed.), Ha Noi, 2006.
Ministry of Health, Vietnam, Follow-up study on diabetic complications in patients since their first presentation at National Hospital of Endocrinology, TaVan Binh (Ed.), Ha Noi, 2006.
Prevalence of undiagnosed type-2-diabetes mellitus and impaired fasting glucose in German primary care: data from the German Metabolic and Cardiovascular Risk Project (GEMCAS).
L. Gardete-Correia, J. Boavida, J. Raposo, S. Massano-Cardoso, C. Mesquita, C. Fona, et al., Diabetes Prevalence Study in Portugal. National Diabetes Program (unpublished data, personal communication) (2009).
Estimation of the prevalence of diagnosed diabetes from primary care and secondary care source data: comparison of record linkage with capture–recapture analysis.
b L. Gardete-Correia, J. Boavida, J. Raposo, S. Massano-Cardoso, C. Mesquita, C. Fona, et al., Diabetes Prevalence Study in Portugal. National Diabetes Program (unpublished data, personal communication) (2009).
c S. Wild, personal communication, on behalf of the Scottish Diabetes Research Network, Diabetes prevalence estimates for Scotland (2009).
d Organizacion Panamericana de Salud (E. Medina, personal communciation), Prevalence of diabetes in Nicaragua. Managua, 2007.
The highest regional prevalence (Table 3) for 2010 (after age-standardization to the world population) was for North America, followed by the EMME and South Asia. The African region is expected to have the largest proportional increase in adult diabetes numbers by 2030, followed by the EMME, though North America will continue to have the world's highest prevalence. Every region will have an increase in numbers well in excess of adult population growth, and total numbers with diabetes are likely to increase by 50% over the 20 years.
Considering only the 91 countries in which prevalence studies have been undertaken, 5 of the 10 world's highest national prevalences occur in the Middle-East (Table 4), although only Saudi Arabia (18.7%) is among the 80 most populous. The Gulf States have prevalences similar to that of Saudi Arabia, and 20 of the EMME Region's 22 countries have prevalences above the world 2010 prevalence of 6.4%.
Table 4Top 10 countries for diabetes prevalence in 2010 and 2030.
2010
2030
Country
Prevalence (%)
Country
Prevalence (%)
1
Nauru
30.9
Nauru
33.4
2
United Arab Emirates
18.7
United Arab Emirates
21.4
3
Saudi Arabia
16.8
Mauritius
19.8
4
Mauritius
16.2
Saudi Arabia
18.9
5
Bahrain
15.4
Reunion
18.1
6
Reunion
15.3
Bahrain
17.3
7
Kuwait
14.6
Kuwait
16.9
8
Oman
13.4
Tonga
15.7
9
Tonga
13.4
Oman
14.9
10
Malaysia
11.6
Malaysia
13.8
Only includes countries where surveys with blood glucose testing were undertaken for that country.
Table 5 shows the 10 countries with the largest numbers of people with diabetes. As might be expected, the countries with the largest populations have the highest number of persons with diabetes. Only Bangladesh and Nigeria of the world's 10 most populous countries are not among the 10 countries with the highest diabetes numbers (replaced by Germany and Mexico) for 2010.
Table 5Top 10 countries for numbers of people aged 20–79 years with diabetes in 2010 and 2030.
There are marked differences between developed and developing countries. Fig. 1 shows current estimated numbers of people with diabetes by age-group for 2010 and 2030. For developing countries, adult diabetes numbers are likely to increase by 69% from 2010 to 2030, compared to 20% for developed countries, whereas total adult populations are expected to increase by 36% and 2% respectively. For the developing countries, increases in diabetes numbers are expected for each age-group, with a doubling for the over 60-year age-group. For developed countries, an increase (38%) is only expected amongst the over 60s, with slight decreases predicted for the younger age-groups. Currently, the greatest number of people worldwide with diabetes is in the 40–59 year-old age-group, but by 2030, there will be slightly more people with diabetes in the 60–79 year-old age-group.
Fig. 1Numbers of adults with diabetes in developed and developing countries in 2010 and 2030, according to age-group.
The overall total predicted increase in numbers with diabetes from 2010 to 2030 is 54%, at an annual growth of 2.2%, which is nearly twice the annual growth of the total world adult population. Thirty-six percent of the anticipated absolute global increase of 154 million people with diabetes is projected to occur in India and China alone.
4. Discussion
These estimates suggest that in 2010 there will be 285 million people worldwide with diabetes, with considerable disparity between populations and regions. The pattern of diabetes varies considerably according to countries’ economic status. For developed countries, the majority with diabetes are aged over 60 years, whereas for developing countries most people with diabetes are of working age, between 40 and 60 years. This difference is likely to still be present in 2030, although less marked, as the average age of developing countries’ populations will increase slightly more than in the developed countries. Population growth, ageing of populations, and urbanization with associated lifestyle change is likely to lead to a 54% increase in worldwide numbers with diabetes by 2030.
These projections are somewhat higher than predictions made only a few years ago [
], but doubt that this is the cause for the increase in prevalence, as prevalences tended to be similar for those countries based on the same original studies, but differed when based on different reports (which applied for the majority of cases). We believe that the increases reported in the current estimates are likely to relate to the use of more recent studies, most of which reported higher prevalences than earlier studies; this was the case for a number of the largest countries, with newer reports showing higher prevalences for India [
Prevalence of diabetes and impaired fasting glucose in the Chinese adult population: International Collaborative Study of Cardiovascular Disease in Asia (InterASIA).
Thus, the likeliest explanation for the differences is that prevalence is genuinely increasing, as a consequence of increasing incidence (due to demographic changes such as ageing, and as the undesirable result of risk factors such as obesity and sedentary life becoming more common), and also a result of better health care improving longevity of people with diabetes.
We have not addressed the issues of changing incidence, nor whether medical care will increase lifespan with diabetes. We have based our projections for 2030 on predicted demographic changes: urbanization and ageing. Urbanization in developing countries is associated with a more sedentary lifestyle tending to increase diabetes prevalence [
], so to some extent is a proxy for lifestyle changes. The challenge is to minimize the detriments of urbanization, as the process is unlikely to be reversed. Specific lifestyle intervention programs have been shown to be efficacious [
The Indian Diabetes Prevention Programme shows that lifestyle modification and metformin prevent type 2 diabetes in Asian Indian subjects with impaired glucose tolerance (IDPP-1).
] in reducing diabetes incidence. Apart from the impact of urbanization, we have not attempted to account for the effects of changes in risk factors (e.g. obesity), as accurately assessing the relationship between risk factors and diabetes is difficult across the diverse global population. Thus, if the prevalence of obesity and other risk factors continue to rise, it is likely that the estimates presented here will be lower than the actual figures.
The principal issue of course is the accuracy of our estimates. The major limitations are paucity of data, which applies varyingly throughout the world, and the representativeness of studies chosen. Thus, only 37 out of the 133 studies were national studies, with only two of these (Iceland, Turkey [
]) in Europe. Studies were only available from 5 out of 50 sub-Saharan African countries, and data from Poland were used for 7 Eastern European countries. There is a clear need for more studies on the prevalence of diabetes. We can have most confidence in results from regions where repeated surveys have shown similar patterns. This particularly applies to the Middle-East, and small Pacific Island states, where a number of surveys has quantified the problem.
The worldwide pattern is dominated by large countries, and these data highlight the extent to which demographic changes in India, China and Brazil are likely to affect the total numbers with diabetes. Each of these countries has had relatively recent national surveys, so that the likelihood of unrepresentative data is reduced.
In summary, these results serve as another piece of evidence that diabetes is continuing to be an increasing international health burden. The estimates here are higher than those previously made [
], which supports the concern that they were conservative, and that the prevalence of diabetes continues to rise. Ageing and urbanization are increasingly adding to the burden of diabetes in developing countries, where resources for dealing with the associated clinical problems are most scarce.
Conflict of interest
There are no conflicts of interest.
Acknowledgements
The authors would like to thank the members of the IDF Diabetes Atlas Committee (JC Mbanya, D Gan, B Allgot, K Bakker, J Brown, A Ramachandran, M Silink, L Siminerio, G Soltesz, R Williams) for their advice in compiling these estimates. Funding was provided by the IDF.
World Health Organization, Definition, diagnosis and classification of diabetes mellitus and its complications. Part 1: diagnosis and classification of diabetes mellitus. Department of Noncommunicable Disease Surveillance, Geneva, 1999. Report No.: WHO/NCD/NCS/99.2.
Prevalence of diabetes and impaired fasting glucose in the Chinese adult population: International Collaborative Study of Cardiovascular Disease in Asia (InterASIA).
The Indian Diabetes Prevention Programme shows that lifestyle modification and metformin prevent type 2 diabetes in Asian Indian subjects with impaired glucose tolerance (IDPP-1).
Ministry of Health, Republic of Indonesia, National Basic Health Research 2007, Official Report (translated from RISKESDAS 2007, Sidartawan Soegondo), Jakarta, 2008.
Ministry of Health, Vietnam, Follow-up study on diabetic complications in patients since their first presentation at National Hospital of Endocrinology, TaVan Binh (Ed.), Ha Noi, 2006.
Prevalence of undiagnosed type-2-diabetes mellitus and impaired fasting glucose in German primary care: data from the German Metabolic and Cardiovascular Risk Project (GEMCAS).
Estimation of the prevalence of diagnosed diabetes from primary care and secondary care source data: comparison of record linkage with capture–recapture analysis.
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