Diabetes Incidence and Historical Trends

The Summary

Diabetes Incidence and Historical Trends

In 2021, there were about 529 million people living with diabetes worldwide, according to the Global Burden of Disease Study (GBD 2021 Diabetes Collaborators, 2023).

The International Diabetes Federation Diabetes Atlas publishes diabetes prevalence numbers worldwide. 

Both the incidence  and prevalence of type 1, type 2, and gestational diabetes has increased over the past decades, worldwide. The The worldwide incidence of diabetes (type 1 and 2) increased by 102.9% between 1990-2017), from 11,303,084 new cases diagnosed in 1990 to 22,935,630 new cases in 2017 (which translates to almost 63,000 people who were newly diagnosed with diabetes per day in 2017!) (Liu et al. 2020). There is some evidence of recent plateaus in type 1 diabetes and type 2 diabetes incidence in some countries.

It is estimated that in 2021 there were 355,900 total new cases of type 1 diabetes globally among children and adolescents, of which 56% were diagnosed. This number is projected to increase to 476,700 in 2050 (Ward et al. 2022). 

This page looks at these trends in more detail, focusing on type 1 diabetes, and includes information on ethnicity, age, gender, seasonality, and geography, as well as type 1 diabetes clusters-- yes, clusters do exist.

None of the environmental factors linked to type 1 diabetes so far appear to be able to explain the increasing incidence trends (Norris et al. 2020), except, I would argue, environmental chemical exposures. 

The Details

Type 2 Diabetes Incidence and Prevalence

Worldwide

For the most current information on the number of people with type 2 diabetes around the world, see the International Diabetes Federation Diabetes Atlas. Here are some numbers:

• •  About 536 million, or 10.5% of adults in the world had diabetes in 2021 (Sun et al. 2021). Those numbers increased from  463 million, or 9.3% in 2019 (Saeedi et al. 2019), 451 million in 2017 (Cho et al. 2018), and 415 million in 2015 (Ogurtsova et al. 2017). Clearly different studies have different estimates, we don't know exactly how many people it is, but it's a lot.

  • ~80% of people with diabetes live in low- and middle-income countries.

  • About half of adults worldwide with diabetes did not know they had it (undiagnosed diabetes) (Ogurtsova et al. 2021).

However, since 2010 many countries show a levelling off or even decrease in type 2 diabetes incidence (at least in higher income countries) (Magliano et al. 2021). Unfortunately there is still rapid growth of type 2 diabetes in low and middle income countries (Liu et al. 2022). In China, nearly 50% of adults had diabetes or prediabetes in 2013 (Wang et al. 2017). In adolescents and young adults, type 2 diabetes incidence continues to rise globally, especially in low and middle income countries (Luo et al. 2024; Xie et al. 2022). In the UK, the number of people under 40 diagnosed with type 2 has increased by almost 40% in less than 5 years; globally the prevalence of type 2 in young adults increased from 2.9% to 3.8% of people from 2013 to 2021 (The Lancet Diab and Endo, 2024).

U.S.A.

Of U.S. adults, 12-14% have type 2 diabetes (in 2011-12). The numbers are higher for Blacks, Hispanics, and Asians than for whites. The prevalence of diabetes in the U.S. has increased over the past few decades (it was 9.8% in 1988-1994) (Menke et al. 2015). The good news, however, is that in U.S. adults since 2009, diabetes prevalence has flattened out, and incidence has actually decreased (especially in non-Hispanic whites). However, rates are still high, and obesity continues to increase (Benoit et al. 2019). In fact, in many developed countries, the increasing type 2 diabetes incidence may be leveling out. From 2006-14, increasing trends were found in only 33% of populations, whereas 30% and 36% had stable or declining incidence (these data are mostly from higher income countries) (Magliano et al. 2019). For more on this study, see article in Medpage Today, Is Diabetes Becoming Mainly a Third World Problem?— Incidence declines seen predominantly in high-income countries.

For current U.S. numbers, also see the CDC's National Diabetes Statistics Report.

In U.S. youth, the latest data show that the prevalence of type 2 diabetes increased by over 30% between 2001 and 2009 (Dabelea et al. 2014). In addition, nearly 1 in every 5 U.S. teenagers has abnormally high blood glucose levels (Menke et al. 2016). Between 2015 and 2018, 28% of U.S. adolescents had prediabetes, up from 12% between 1999 and 2002 (Liu et al. 2022). In fact, in the U.S., the rates of type 2 diabetes in children are now increasing faster than type 1 diabetes: between 2002 and 2012, the incidence of type 2 diabetes in children increased by 4.8% per year, and was especially high in minority groups (Mayer-Davis et al. 2017). As of 2016, about 1 of 5 adolescents and 1 of 4 young adults had prediabetes (Andes et al. 2019). Additional evidence shows that in U.S. children and adolescents, the prevalence of type 2 diabetes nearly doubled from 2001 to 2017, especially in Black and Hispanic youth (Lawrence et al. 2021). In U.S. youth, between 2002 to 2018, type 2 diabetes incidence increased at 5.3% per year. Minority groups had higher rates of increase (Wagenknecht et al. 2023). In 2020, about 3% of children and 5% of adolescents worldwide had metabolic syndrome, a cluster of conditions related to type 2 diabetes and obesity (Noubiap et al. 2022).

In the U.S., racial minority groups tend to have the highest incidence of type 2 diabetes. The cause of these differences is not known; certainly diet, an unsafe environment, poverty, and lifestyle could play a role, as could exposure to environmental chemicals (Golden et al. 2019; Sargis and Simmons, 2019). In the U.S., racial minority groups tend to develop type 2 diabetes at a lower body weight (BMI) than whites (Zhu et al. 2019). The racial disparities in type 2 diabetes are expected to continue into the future (Tönnies et al. 2023). In U.S. adults, diabetes is becoming more common among lean people, especially minorities and women (Adesoba and Brown, 2023).

In the U.S., subgroups within various racial groups also have a differing prevalence of type 2 diabetes. In a sample of U.S. adults, the prevalence of total diabetes was 12% for non-Hispanic whites, 20% for non-Hispanic Blacks, 22% for Hispanics, and 19% for non-Hispanic Asians. Among Hispanic adults, the prevalence of total diabetes was 25% for Mexicans, 22% for Puerto Ricans, 21% for Cuban/Dominicans, 19% for Central Americans, and 12% for South American subgroups. Among Asians, the prevalence of total diabetes was 14% for East Asians, 23% for South Asian, and 22% for Southeast Asian subgroups. The prevalence of undiagnosed diabetes was 4% for non-Hispanic whites, 5% for non-Hispanic Blacks, 8% for Hispanics, and 8% for Asians (Cheng et al. 2019).

Preschoolers with Type 2? Really?

Really. In Texas, perhaps the youngest person ever to develop type 2 diabetes was 3 1/2 years old. It was caught early and reversed with dietary changes and metformin (Yafi et al. 2015). Also in Texas, a 5 year old was also diagnosed with type 2 diabetes (Hutchins et al. 2017). While these cases are rare enough to merit publication as case studies, the trend is alarming!

Obesity

Obesity has been increasing over the past 50 years. In U.S. children, more than 1 in 5 have obesity; between 2011 and 2020 the childhood obesity rate increased from around 18% to over 21% (Hu and Staiano, 2022). In 2022, the U.S. obesity rate in adults may have plateaued (Rader et al. 2024).

In the U.S., as elsewhere, type 1 diabetes prevalence varies by race or ethnicity. For example, the Hispanic Community Health Study/Study of Latinos (HCHS/SOL), of four U.S. locations, found that the overall prevalence of type 1 diabetes in Hispanics/Latinos was 1.8/1000 persons. This is similar to the estimates obtained through other studies, such as NHANES (2.6/1000) and the SEARCH for Diabetes in Youth Study (1.5/1000). The prevalence varying by specific Hispanic/Latino background, and is highest in people of Dominican ancestry (Kinney et al. 2019). Note that each of these studies uses different definitions of type 1 diabetes, based on criteria such as age of onset or insulin use, and are not necessarily based on a doctor's diagnosis, autoimmune antibody testing, c-peptide testing, or other more accurate measures of type 1 diabetes diagnosis. We really need better diagnosis and tracking of type 1 diabetes in the U.S.!

The prevalence of type 1 also varies a lot by state (among those with private insurance), to see the prevalence in your state, see here: Rogers et al. 2018. Expect more numbers in the future, as researchers are figuring out ways to determine exactly how many children have type 1 (or type 2) diabetes in the U.S. using electronic health records (Zhong et al. 2016). I wish them luck!

Trends Over Time

Worldwide, the incidence of type 1 diabetes increased, on average, 3% per year between 1960 to 1996 in children under age 15 (Onkamo et al. 1999). Between 1990 and 1999, incidence increased in most continents, with a rise of 5.3% in North America, 4% in Asia, and 3.2% in Europe. This trend is especially troubling in the youngest children; for every hundred thousand children under age 5, 4% more were diagnosed every year, on average, worldwide (Diamond Project Group 2006). Between 1989-2013, on average in Europe, a continued 3.4% annual increase continues, despite a slower rate of increase in some high-incidence countries (Patterson et al. 2018); the annual rate of increase varied by country from 0.6 to 6.6% per year, with the lower incidence countries showing the higher rates of increase (Svensson et al. 2022).

In the U.S., the prevalence of type 1 diabetes increased by 21% in children between 2001 and 2009 (Dabelea et al. 2014), and the incidence of type 1 diabetes in non-Hispanic whites increased by 2.7% per year between 2002 and 2009 (Lawrence et al. 2014). More recent numbers show that overall, type 1 diabetes incidence in children increased by 1.8-1.9% per year between 2002 and 2012 (Mayer-Davis et al. 2017), and continuing into 2015 (Divers et al. 2020). In U.S. youth, between 2002 to 2018, type 1 diabetes incidence increased at 2% per year, and minority groups had higher rates of increase than whites (Wagenknecht et al. 2023). Those numbers are from the SEARCH for Diabetes in Youth study, which has study centers in 5 U.S. states. More data from SEARCH shows that type 1 prevalence in U.S. children and adolescents increased by 45% between 2001-2017, especially in whites and Blacks (Lawrence et al. 2021). In those who use Medicaid, the annual prevalence of type 1 diabetes in children increased continuously from 2002 to 2016 (Chen et al. 2019).

A study of a large population of U.S. patients with commercial health insurance found that type 1 (and type 2) prevalence increased between 2002-2013 in children (Li et al. 2016). Another study of U.S. patients-- both children and adults-- with commercial health insurance found that the type 1 diabetes incidence rate increased 1.9% in children between 2001 and 2015, and varied by area. The incidence decreased during that same time period in adults, although more people are diagnosed as adults than as children. They estimate that the number of new cases of type 1 diabetes (ages 0-64 years) in the U.S. is 64,000 annually (27,000 cases in youth and 37,000 cases in adults), which is more than previously thought (Rogers et al. 2017). 

Data from the Children's Hospital of Alabama show that there was an increase in type 1 incidence between 2000-2017, with an annual percent change of 10% from 2000-2007 and a 1.7% decrease from 2007-2017. The incidence for whites and Blacks both increased, with an average annual percentage change of 4.4% and 2.8%, respectively. The increase plateaued in 2006 for whites and 2010 for Blacks (Correya et al. 2019).

There has been a general increase in type 1 incidence during the COVID-19 pandemic, see the Viruses page for more info.

Can Genes Alone Explain the Increasing Incidence?

No.

Essentially all researchers agree that changes of this magnitude cannot be explained by genetic changes alone. In fact, studies are finding that high risk susceptibility genes for type 1 diabetes are becoming less frequent over time in children, while more children with low to moderate risk genes are developing the disease more now than in years past (Fourlanos et al. 2008; Gillespie et al. 2004; Hermann et al. 2003; Resic-Lindehammer et al. 2008; Steck et al. 2011; Vehik et al. 2008). An interesting study from Poland analyzed susceptibility genes from exhumed skeletons from the Middle Ages, and found that genetic predisposition to type 1 diabetes is lower today than it was 700 years ago (Witas et al. 2010).

It is also clear that the trend varies by year and by location, implying environmental factors are critical. The rates of increase are not uniform within Europe or within countries, suggesting that different risk factors vary over time in different countries (Patterson et al. 2012).

Genes probably do play a role in the geographical variations in type 1 diabetes incidence around the world. Yet even some studies find that genetics do not necessarily play a large role in some of these variations (e.g., Santana Del Pino et al. 2017).

One Israeli study found that the average annual percent change in type 1 diabetes incidence increased by 1.9% in people with a first-degree relative with type 1, and decreased by 0.2% in people without a first-degree relative with type 1, suggesting that environmental factors impose higher diabetogenic pressure in people with genetic susceptibility (Zung et al. 2018). I haven't seen any other studies addressing the question of whether or not the rise in type 1 incidence is faster in a genetically susceptible population.

When Did the Incidence Start to Rise?

Around World War 2, in developed countries, but more recently in later developing countries.

The incidence of type 1 diabetes has been rising in children since about the mid-20th century in many European and North American countries (Gale 2002). What has changed during this time period? A number of things changed that may influence the development of type 1 diabetes, including: breastfeeding rates, diet, height and weight, vitamin D levels, infectious disease, vaccines, earlier puberty, factors relating to gestation and birth, and more. A major change that has garnered less attention in studies of type 1 diabetes is environmental chemicals. Yet perhaps we should pay attention: the historical patterns of contamination are consistent with historical patterns of type 1 diabetes incidence. While correlation is not the same as causation, the pattern is certainly consistent.

The rise in type 1 diabetes incidence is coincidental with the large-scale production and use of many industrial and agricultural chemicals. Like the rising incidence of type 1 diabetes, large-scale chemical production also began around the middle of the 20th century. In 1975 about 60,000 chemicals were manufactured or processed in the U.S.; in 1997 there were over 75,000 (Endocrine Disruptor Screening and Testing Advisory Committee (1998) Final Report U.S. EPA). Chemical production increased during this time as well.

Is the Increasing Type 1 Diabetes Incidence Leveling Off?

Maybe, depending on where you live, but it is not clear yet.  

A study from Sweden provides some hope that the trend is leveling off: it found that incidence was increasing in children born through the year 2000, but after that the trend might be flattening (Berhan et al. 2011). Newer data show that the trend in Sweden has flattened out at a high level (from 2005 to 2019), and that immigration has not affected this pattern (Waernbaum et al. 2022). Data from Norway show that the rising incidence has essentially leveled off since 2004 (Skirvarhaug et al. 2014). Data from Italy also show that the increase is starting to level off in more recent years (Bruno et al. 2013; Di Ciaula 2016). Data from Ireland show that the rising trend has leveled off since around 2008 (Roche et al. 2016; McKenna et al. 2021), although more recent numbers show it is rising again (Roche et al. 2023). Wales also shows a leveling off (Harvey et al. 2021), as does Scotland (Thomson et al. 2023), and the north east of England actually shows a decline (Hayes et al. 2023). However overall in England and Wales apparently it's still increasing (Ng and Soni, 2023). In the Netherlands, the incidence in children under 5 appears to have stabilized around 1996-99 (Spaans et al. 2015). In Poland, the rising incidence over the past 24 years shows a "slight" leveling off around 2010 (Chobot et al. 2017), although another study finds increasing incidence through 2018 (Niechciał et al. 2024). In the Czech Republic, the incidence stopped rising-- in children under 5, it was rising 15% per year from 1996-2001, and then flattened out from 2002-2009 (Cinek et al. 2012). And in Australia, data indicates a possible leveling off, after a peak in 2003 (Haynes et al. 2018), with an actual decrease in incidence among 0-4 year olds (Haynes et al. 2020), but increasing incidence in 10-14 year olds (Zhang et al. 2023). In New Zealand, data shows a leveling off in 0-4 year olds since 2003, but not in older children (Flint et al. 2021), and overall a stable incidence (Wu et al. 2023). In Austria, incidence increased from 1989 to 2012, but then leveled off overall, due to a declining incidence in 0-4 year olds (in older ages, incidence is still increasing) (Rami-Merhar et al. 2020).

Spain also shows a leveling off (Forga et al. 2018a; Goñi Iriarte et al. 2023; Rodríguez Escobedo et al. 2023), following a long-term rise (Forga et al. 2018b). Mexico shows an actual decrease from 2006-2018, following a rise from 2000-2006 (Wacher et al. 2019). In Poland, incidence increased from 2006 to 2012, and then fell a bit through 2017 (Wasyl-Nawrot et al. 2020), although a different Polish study found an increase from 2000-2019 (Zubkiewicz-Kucharska et al. 2021). In Hong Kong, incidence is still increasing, but the rate of increase had slightly decreased in recent years. The annual increase in incidence changed from 4.3% per year (1997-2007) to 3.5% per year (2008-2017) (Tung et al. 2020). In Germany, there is a possible/probable leveling off (Buchmann et al. 2023; Manuwald et al. 2021; Baechle et al. 2022; Stahl-Pehe et al. 2022).

Data from Finland, which has the highest type 1 diabetes incidence rate of any country in the world, show that type 1 incidence appears to have increased even more rapidly since the mid-1990s than in earlier decades, through 2005 (Harjutsalo et al. 2008). Additional data, however, show that between 2003 and 2018, the incidence actually decreased, due to a decreasing incidence in the youngest age group (Parviainen et al. 2020). It seems like the peak of Finland's incidence was in 2006 (Knip 2021).

In Denmark, type 1 diabetes incidence continues to rise (through 2014) at about 3% per year (Svensson et al. 2016), although another study finds that there has been an overall decrease between 1996 and 2016, with an increase in people under age 25 diagnosed but a decrease in older people (Carstensen et al. 2021). (Most studies only look at incidence rates in children, so this is interesting-- maybe we would know more if people would look at incidence rates in adults... 

Incidence continues to rise in Sardinia, Italy-- which may have overtaken Finland as the area with the highest incidence in the world-- (Ripoli et al. 2024), Canada (Cohen et al. 2021; Fox et al. 2018), France (Piffaretti et al. 2018), Kuwait (Shaltout et al. 2017), Romania (Vlad et al. 2018), Chile (Garfias et al. 2019), Qatar (Alyafei et al. 2019; Soliman et al. 2022), Turkey (Esen and Okdemir, 2020; Özalkak et al. 2022), Slovakia (Podolakova et al. 2020), Hungary (Barkai et al. 2019), Hong Kong (Luk et al. 2020), Poland (Głowińska-Olszewska et al. 2020), Montenegro (Raicevic et al. 2022), Algeria (Khater et al. 2020), Libya (Khashebi et al. 2023), Korea (Chae et al. 2020), Japan (Matsuda et al. 2023), North Africa and the Middle East (Esmaeili et al. 2022), Iran (Babakhanian et al. 2022; Bandarian et al. 2023; Hashemipour et al. 2023), and Brazil (Negrato et al. 2017) as well.

In the U.S., type 1 diabetes incidence in children may also be leveling off, from 2007-2012 (Rush et al. 2018). Earlier data from the U.S. show that as of 2000-2004, incidence of type 1 (and type 2) diabetes in children was still increasing significantly, and has been since the 1980s (in both Philadelphia (Lipman et al. 2013), and Colorado (Vehik et al. 2007). (See chart above for other U.S. data as well). In Rochester, Minnesota, the incidence of type 1 actually hasn't risen since 1970, although youth-onset type 2 roles significantly (Bai et al. 2024). In U.S. 0-4 year olds, the incidence declined 3.4% annually from 2006-2017 (which could be associated with the introduction of the rotovirus vaccine in 2006) (Rogers et al. 2019). In Australia, type 1 diabetes incidence also declined after the rotovirus vaccine was introduced (Perrett et al. 2019). (See the Vaccines page for more information). In U.S. adults, considering type 1 and 2 combined, the incidence doubled during 1990-2008, but leveled off between 2008 and 2012. However incidence continues to rise in Blacks and Hispanics (Geiss et al. 2014). 

It also appears that type 1 diabetes is progressing faster than before. A large study from the U.S. and Europe found that disease progression seems to have increased over the past 27 years in children newly diagnosed with type 1 diabetes (Max Andersen et al. 2014).

In China, meanwhile, the incidence of type 1 diabetes is skyrocketing (Fu et al. 2013). Between 1997-2011, type 1 diabetes incidence increased 14.2% per year (!) in Shanghai's children. At that rate, the incidence of type 1 would double in just four years (between 2016 and 2020), and prevalence would sextuple by 2025 (Zhao et al. 2014). In Zhejiang, China (just south of Shanghai), incidence increased 12% per year between 2007 and 2013. Even worse, incidence increased by over 33% per year in children under 5 years old! (Wu et al. 2016). Data from Beijing show more modest rates of increase (but still concerning) of 5% per year, and 7% per year in the youngest age group, between 2011-2020 (Li et al. 2023). Although another study shows a more gradual increase in type 1 in one hospital in China (Wu et al. 2024). In the western Pacific region (including China), the incidence seems to be continuing to increase (Wang et al. 2023).

Poland has an increasing incidence by 12.7% per year from 2010 to 2014, especially in urban areas (Szalecki et al. 2018). Algeria also shows a steep rise of 12.8% from 1973-2017 (Touhami et al. 2019).

Geographic Variations

Of the 500,000 children with type 1 diabetes in the world, the most live in Europe (129,000) and North America (108,700). Countries with the highest estimated numbers of new cases annually (highest incidence) were the United States (13,000), India (10,900) and Brazil (5000) (Patterson et al. 2014). In the U.S., an estimated 191,986 U.S. youth under age 20 have diabetes; 166,984 have type 1 diabetes; 20,262 have type 2 diabetes; and 4,740 have "other types" (Pettitt et al. 2014). In 2017, Globally, type 1 diabetes represents about 2% of the estimated total cases of diabetes, ranging from less than 1% in certain Pacific countries to more than 15% in Northern Europe. Global numbers of incident and prevalent cases of type 1 diabetes were estimated to be 234,710 (newly diagnosed each year) and 9,004,610 (the number of people with type 1), respectively, in 2017 (Green et al. 2021).

A worldwide survey found that for the 0–19 year age group, the highest incidence was in Northern Europe (39.0 people diagnosed each year per 100,000 people), Northern America (20.07 per 100,000), and Northern Africa (10.1 per 100,000), while the lowest was observed in Eastern and Western Africa (< 2 per 100,000). For 0-14 year olds, the highest incidence was reported in Northern Europe (23.96 per 100,000), Australia/New Zealand (22.8 per 100,000), and Northern America (18.02 per 100,000), while the lowest was observed in Melanesia, Western Africa, and South America (all < 1 per 100,000) (Gomber et al. 2022; Larkin 2022).

Type 1 diabetes incidence ranges from very low in South America and Asia, to very high in Europe, especially northern Europe (Onkamo et al. 1999). Finland, Sardinia (Italy), and Sweden have the highest incidence of type 1 diabetes in the world (Diamond Project Group 2006, Patterson et al. 2014, Tuomilehto 2013). In fact, the longer you live in Sweden, the higher your risk of type 1 diabetes-- offspring of immigrant women living in Sweden for 11 years or more have a 22% higher risk than offspring of women living in Sweden for 5 years or less (Hussen et al. 2015). Other countries show changes in incidence when after immigration, for example, immigrants to Israel from lower incidence countries lose their protection against diabetes around adolescence; the younger they are when the immigrate, the more likely they are to get type 1 (Peled et al. 2017). In Italy, migrants from North Africa actually have a higher incidence than the locally born Italian children (Maltoni et al. 2022).

As an example of a country with low incidence, children in Dar es Salaam in Tanzania have very low incidence of type 1 diabetes, at 1.5 people diagnosed per 100,000 people, which is much lower than rates for Black children in the U.S., Virgin Islands, or Cuba. In Tanzania, only one child under age 5 was diagnosed during one 10 year study period (Swai et al. 1993). In Ghana, rates remain low, although there have been some changes over time, with increasing rates in adolescents but decreasing rates overall (from 1992-2018) (Sarfo-Kantanka et al. 2020). Mali also has low but increasing rates (Sandy et al. 2021). Burkina Faso also has low but increasing rates (Sagna et al. 2024). The Sudan, however, has higher rates than most other African countries (Saad et al. 2020), and Algeria has a high incidence (Khater et al. 2020). In general, the incidence of type 1 is low but increasing in sub-Saharan African, the Middle East, and North Africa (Zhang and Luo, 2024). The Raikas, a tribal group in India, have a far higher genetic risk of type 1 diabetes than other North Indians, yet the incidence of type 1 is almost nil (Bhat et al. 2014)-- implying that genetics do not tell the whole story. 

Type 1 vs Type 2 Diabetes in Children

Previously unheard of, children are now developing type 2 diabetes. Even children under 10 years of age are now developing type 2 diabetes (Pettitt et al. 2014).

Within the U.S., there are ethnic differences in diabetes prevalence. In children under age 20, type 1 diabetes is more common (prevalent) among non-Hispanic whites, followed by Blacks, Hispanics, and Asian/Pacific Islanders, and lowest in American Indians. Among these same children, type 2 diabetes, on the other hand, is more common among American Indians, followed by Blacks, Asian/Pacific Islanders, and Hispanics, and lowest in non-Hispanic whites (Liese et al. 2006, Pettitt et al. 2014). In the U.S., type 1 diabetes is still more common in children than type 2 diabetes, with the exception of American Indian youth age 15-19, where type 2 is more prevalent than type 1 (Pettitt et al. 2014).

In China, type 2 diabetes in children has doubled in prevalence in the past 5 years, and now even surpasses the prevalence of type 1 diabetes in children (Fu and Prasad 2014).

What About Adults?

A review of adult-onset type 1 diabetes from 32 countries and regions found that: 1) there is a lack of data, particularly in low- and middle-income countries; 2) the incidence of adult-onset type 1 diabetes is lowest in Asian and highest in Nordic countries; 3) adult-onset type 1 is higher in men versus women; 4) it is unclear whether adult-onset type 1 incidence declines with increasing age; and 5) it is unclear whether incidence of adult-onset type 1 has changed over time (Harding et al. 2022). A more recent study found that the prevalence of type 1 diabetes is increasing in older adults (over 65) worldwide, but that there is a higher life expectancy and lower mortality (Yang et al. 2024).

Most studies of type 1 diabetes only consider children under the age of 15. A recent study that looked at all new cases of diabetes diagnosed during a 3 year period in an area of Sweden, and actually tested people of all ages for antibodies, found that type 1 incidence peaked during ages 0-9 and then again at ages 50-80, showing that disease onset is not limited to children. In fact, nearly 60% of new type 1 cases were diagnosed in people over age 40 (Thunander 2008). A large UK study found that 42% of type 1 diabetes cases (defined by genetics) were diagnosed in people aged 31-60 (Thomas et al. 2018). In Iceland, population-wide, the number of adults diagnosed with type 1 is about half that of the number of children (Halldora Thordardottir et al. 2019).

A review of studies from around the world of type 1 diabetes in people over 15 years of age found that geographical variations mirrored that of type 1 diabetes in children, that more adult males were diagnosed than adult females, and that overall incidence tends to decrease after age 14 (Diaz-Valencia et al. 2015). 

What about changes over time? As discussed above, incidence of type 1 diabetes among children is increasing over much of the world. Yet one study from Belgium makes an interesting point. That study was one of the few that included people over 14 years old, and the researchers found that even though there had been an increase in type 1 diabetes incidence for 0-14 year olds, there was no overall increase in incidence over the 12 year period, because fewer people over 14 were being diagnosed. In 0-4 year olds, the annual increase in incidence was 5%. This finding implies that at least in Belgium, the increasing incidence in type 1 in children may be due to an acceleration of the disease process, but not an overall increase in incidence (Weets et al. 2002). A follow-up study found that the rising incidence in Belgian children was largely due to an increase in incidence in boys under 10, but not girls (Weets et al. 2007).

Another study shows a similar finding: that during the period of 1983-1998 in Sweden, the incidence of type 1 diabetes did not show an overall increase in the 0-34 year age group, but instead, the average age at diagnosis decreased. A shift to younger age at diagnosis seems to explain the increasing incidence of type 1 diabetes in Sweden during this time period (Pundziute-Lyckå et al. 2002). More recent data from Sweden, covering the period from 1983-2007, shows that incidence was higher in children under age 15, which peaked and then declined, while there were decreases in the older age groups (25-34 years), suggesting that there was a shift to a younger age of onset, instead of a uniform rate of increase among all age groups (although the overall incidence is still increasing) (Dahlquist et al. 2011). However, a new look at the Swedish data shows that these previous studies may have underestimated the number of people with type 1 diabetes in the 0-34 age range-- the actual number is 2-3 times higher than previously thought (Rawshani et al. 2014).

Long-term data from Norway from the 1930s to the 1970s show not only that the age of diagnosis decreased, but also that overall incidence increased, in people up to age 30. In the 1930s, diabetes was more common in people aged 15-29 than in people age 0-14, and by the 1970s it was more common in the younger age group instead (Gale 2002; Gale 2005).

A global analysis of type 1 incidence in adolescents and young adults aged 10-24, based on the Global Burden of Disease Study 2019, found that global T1D incidence in this age group increased since 1990 (Gong et al. 2024). In people aged 15-39, most areas of the world showed an increasing incidence of type 1 diabetes ( in Australia, Denmark, Finland, Scotland, South Korea, and Spain, but not in Hungary or Japan (Magliano et al. 2024; Stene 2024).

Until there are more studies that include older age groups, it will be difficult to say how much of the increasing incidence in children is actually due to a decreasing age of diagnosis, and whether or not incidence is also increasing in adults. In the meantime, we can say that type 1 diabetes incidence is increasing in children, especially the youngest children, in countries around the world.

Gender

Unlike many other autoimmune diseases, where females are more at risk of disease, boys and girls under age 15 are diagnosed with type 1 diabetes at relatively equal rates. Some populations with a high incidence tend to have more males than females with type 1, while some with low incidence show more females than males, although this varies among studies. In people of European descent diagnosed at ages 15-40, however, there is a clear male predominance: more men than women are diagnosed with type 1 diabetes at these older ages (Soltesz et al. 2007).

Worldwide, incidence trends generally do not differ between genders-- the incidence of type 1 diabetes is rising in children of both genders (Diamond Project Group 2006).

The "Latitude Rule"

Many of the countries with high incidence are located closer to the polar areas of the globe, both to the north and the south (Soltesz et al. 2007). Even within countries, latitude can make a difference: one Australian study, for example, found that type 1 diabetes was three times more common (prevalent) in more southerly regions of that country than in northerly regions (Staples et al. 2003), as is the case in New Zealand as well (Wu et al. 2023).

Like all rules, however, there are exceptions. For example, Sardinia, Italy's high incidence of type 1 diabetes does not fit the rule. Variations within countries also do not always correspond to latitude (Soltesz et al. 2007).

A study using data from 72 countries found that those at higher latitudes and with less sunshine had higher rates of type 1 diabetes. They also found that incidence was higher in countries with "oceanic" climates (Chen et al. 2017).

Vitamin D, which is produced by the skin when exposed to sunlight, is a possible explanation for this pattern. In a study of 51 regions around the world, Mohr et al. (2008) found that areas with lower levels of ultraviolet B radiation (the main source of vitamin D in humans) had a higher incidence of type 1 diabetes. Vitamin D deficiency appears to be a risk factor for type 1 diabetes, and vitamin D cannot be produced adequately by the skin during the winter in areas closer to the polar regions. In Sweden, a study has found that temperature is more important than sunshine in explaining the higher incidence in the northern parts of that country. Cold weather may increase insulin resistance and exacerbate the disease process (Waernbaum and Dahlquist, 2016). Another possibility is that persistent organic pollutants (POPs) play a role. POPs evaporate and migrate to the polar regions of the earth; some POPs (as well as other chemicals) can even interfere with vitamin D synthesis (see the vitamin D deficiency page).

Wealth

Most countries with high type 1 diabetes incidence are Westernized, developed countries, and the highest incidence countries tend to be the wealthiest countries (Diamond Project Group 2006; Gomez-Lopera et al. 2019; Gomber et al. 2022; Larkin 2022). Even within regions such as Europe, incidence is correlated to gross national product (GNP) and other indicators of national prosperity (Patterson et al. 2001). Some studies have found higher incidence of type 1 in wealthier areas or in people with higher socioeconomic status within countries as well, such as Chile (Torres-Aviles et al. 2010) and the U.S. (D'Angeli et al. 2010).

Why would wealth make a difference in type 1 diabetes incidence? Differences in nutrition or lifestyle may play a role. These factors could include high growth rates in early life (see the height and weight page), improved hygiene and fewer infections (see the viruses page), or more milk consumption (see the wheat and dairy page) (Patterson et al. 2001).

Another possibility seldom considered is environmental chemicals. A number of toxic chemicals are found in plastics, personal care products, and other conveniences of modern life (see, for example, the pages on bisphenol A and phthalates). In developed countries, exposure to bisphenol A is significant and continuous (Welshons et al. 2006). Historically, chemicals such as PCBs were produced in industrialized countries, and now everyone living in developed countries has PCBs in their bodies (Carpenter 2006). While data from less industrialized countries are scarce, in general, people living in more industrialized countries show higher levels of PCBs and dioxins in their bodies than people in less developed countries. In addition, using a measurement of the total toxicity of multiple persistent organic pollutants, levels are higher in people living in industrialized as compared to less developed countries (Sudaryanto et al. 2005; Tanabe and Kunisue 2007). Recently, however, toxic chemicals, pesticides, and chemical wastes, which previously were found only in developed countries, are now used in low and middle income countries, leading to an increased risk of the diseases associated with these chemicals (Suk et al. 2016).

Type 1 diabetes incidence is now rising even in countries with historically low incidence, suggesting a catch-up phenomenon. High incidence countries (e.g., Norway), where incidence rose many decades ago, do not all show a continuing increase in incidence. It is too early to say whether these high-incidence countries have reached a plateau (Gale 2002). Levels of most persistent organic pollutants have declined recently in developed countries. In developing and some former Soviet countries, however, some persistent organic pollutants (like DDT) are still in use, and contamination due to open dumping is also a concern. Levels of some organochlorine pesticides (such as DDT) are now higher in people living in developing countries than in developed nations (Tanabe and Kunisue 2007). Perhaps contamination resulting from industrialization contributed to the rising incidence in many now-developed, high-incidence countries, and other countries, where contamination began later, are now "catching up."

Central and Eastern European countries are one region where type 1 diabetes incidence may be "catching up" to the higher incidence found in Western Europe. For example, in Saxony, East Germany, the incidence has increased since reunification (Manuwald et al. 2017). Over the period of 1989-1998, Central and Eastern European countries showed the highest rates of increasing type 1 diabetes incidence within Europe. Why? Some environmental factors associated with societal development may play a role (Green et al. 2001). Yet because type 1 diabetes takes a long time to develop, the factors responsible for these rapid increases may have operated before the political changes in those countries (EURODIAB ACE Study Group 2000). Environmental contamination is a serious problem in Central and Eastern Europe, beginning during the communist years, before the political changes (Fitzgerald et al. 1998). 

Within or among developed countries, socioeconomic status is also associated with differential chemical exposures. In the U.S., people of higher income levels tend to have higher exposures to mercury, arsenic, perfluoroalkyl substances (PFASs), one type of phthalate, and benzophenone-3 (found in sunscreen). People with lower income levels had higher levels of lead and cadmium, bisphenol A and three phthalates (Tyrrell et al. 2013). Similarly, in Europe, women with higher socioeconomic status have been found to have higher concentrations of several chemicals in their bodies during pregnancy, including mercury, arsenic, PFASs, several phenols, and organophosphate pesticides. Their children also had higher levels of mercury, arsenic, PFASs, organochlorine compounds (persistent organic pollutants), and bisphenol A. Meanwhile, pregnant European women with lower socioeconomic status had higher cadmium exposures during pregnancy, and their children had higher exposures to lead and phthalates (Montazeri et al. 2019).

Clusters

Clustering has been found in type 1 diabetes, meaning that some groups of people living near each other during the same time periods show a higher than expected incidence of disease. Some studies have found clusters of children with higher than expected incidence of type 1 diabetes, and a study from the U.K. found clustering in teenagers as well (McNally et al. 2006).

The Massachusetts Department of Public Health has conducted a cluster investigation on type 1 diabetes in families living in Newton, Wellesley, and Weston, MA. The results were released in Feb. 2012, and are available at this Mass. Dept. Public Health webpage. A cluster of type 1 diabetes was found, but only in certain portions of Wellesley and Weston. MDPH was planning to analyze various environmental factors, including contaminated sites, chemical spills, and pesticide use (on right-of-ways), that potentially could have contributed to this cluster, but I am not sure if they are actually doing this analysis or if it was dropped.

Genetic variations likely explain some of the differing incidence and prevalence rates among people worldwide. Yet even among ethnically similar populations, type 1 diabetes incidence can vary. For example, Finns have a six times higher incidence in type 1 diabetes than Russians living across the border. The genes that confer a high risk of type 1 diabetes, however, are the same in these populations, implying that environmental factors contribute to the differing incidence rates (Kondrashova et al. 2005) Similarly, incidence in northern European countries is higher than in Lithuania and other Baltic states. Yet the genetic risk of type 1 is similar in all of these countries (Skrodenienė et al. 2010). 

In the U.S. state of Utah, the incidence of type 1 diabetes in children increased by 14% between 1998 and 2015, with an annual increase of 0.80%. There were 42 high-risk clusters throughout the state, which were associated with median household income, population density, and latitude (McCullough et al. 2021).

Disease clusters imply the involvement of some environmental factor. Infectious disease and environmental chemicals are two possible suspects. For example, while not type 1 diabetes, a study from Italy found that living closer to an industrial complex was associated with higher fasting blood glucose levels in children (Bansal et al. 2019). Historically, outbreaks of type 1 diabetes have occurred following virus outbreaks, for example in Philadelphia in 1993, where an "epidemic" of type 1 occurred two years after a measles outbreak (Lipman et al. 2002 ).

Urban vs. Rural Areas

There is no consistent pattern of type 1 diabetes being more common in either rural or urban areas. Some studies have found higher incidence in rural areas, and some in more densely populated areas. For example, type 1 diabetes incidence has been found to be higher in more urban areas in Western Australia (Haynes et al. 2006), Poland (Szalecki et al. 2018), and Turkey (Esen and Okdemir, 2020). In New Zealand, type 1 incidence was higher in "satellite urban communities" (Miller et al. 2011). Other studies have found a higher incidence of type 1 in rural areas, such as in England (Sheehan et al. 2020), Germany (Castillo-Reinado et al. 2020), Northern Ireland (Cardwell et al. 2006), Egypt (El-Ziny et al. 2014), Scandinavia (Samuelsson et al. 2019), and the U.S. (Rogers 2019). There are no clear trends in any of these directions. It may depend on the various exposures encountered in each of these areas. For example, the authors of the Egyptian study hypothesize that the higher incidence in rural areas may be due to higher exposures to pesticides.

Other Variations

In Australia, researchers have found that there is a regular 5 year pattern of type 1 diabetes incidence in children. That is, every 5 years there is a peak or trough in the overall incidence rates. Why this is I have no idea (Haynes et al. 2015; Haynes et al. 2012). A Polish study also found a 5 year fluctuation pattern (Chobot et al. 2017). Huh.

What about diabetes complications? South Asians with type 1 diabetes living in India had significantly greater risk of diabetic kidney disease and retinopathy, but a lower risk of neuropathy than white Europeans living in the UK. South Asians in India also had a significantly greater risk of diabetic kidney disease than South Asians living in the UK, but there was no significant difference in the risk of other complications. These finding are the same as are seen in type 2 diabetes (Chetan et al. 2019). This implies that geography may also play a role in the risk of complications from diabetes (although how much is due to different treatment in different areas is a major question for me).

Other Autoimmune Diseases

The incidence of many immune disorders, including many other autoimmune diseases, is rising (Bach 2002). Worldwide, the incidence of celiac disease is rising, and like type 1, this rise is occurring in industrialized countries, and beginning in the latter half of the 20th century (King et al. 2020). In Finland, the increasing incidence of the autoimmune disease multiple sclerosis follows the same pattern as type 1 diabetes as well (Holmberg et al. 2013).

A large UK study found that autoimmune disease is increasing in incidence (from 2000-2019), including celiac disease (Conrad et al. 2023).