Connecting the Dots: Global Epidemiology of Type 1 Diabetes and National Income Levels

Type 1 diabetes mellitus (T1DM), also referred to as juvenile-onset diabetes, is an autoimmune disease that results in the destruction pancreatic β-cells and prevents the normal production of insulin. Unfortunately, T1DM is a complex disease that is not entirely understood, and as such, there are currently no preventative or curative strategies. T1DM affects as many as 3 million Americans and it is estimated that up to 80 US persons are newly diagnosed with T1DM daily. Between 2001 and 2009, the prevalence of T1DM in Americans under the age of 20 rose by 23%, and the rate of T1DM incidence among children under 14 years is said to increase by 3% annually worldwide. With T1DM accounting for approximately $14.9 billion in healthcare costs annually, clinicians and managed care continue to explore management strategies that will improve patient outcomes and quality of life, while driving down health care expenditures.

In today's Joint ADA/JDRF Symposium - Global Epidemiology of Type 1 Diabetes and Implications for Public Health, Jaakko Tuomilehto, MD, PhD, a professor of public health at the University of Helsinki in Finland, presented a session entitled, "Epidemiology of Type 1 Diabetes in Low- and Middle-Income Countries." In his presentation, Dr. Tuomilehto provided a global report that directly compared the changing incidences of T1DM in various countries of differing socioeconomic statuses. Unfortunately, he noted that countries worldwide, regardless of relative income levels, have experienced a gradual increase in new cases of childhood diabetes every year - although some countries, such as those within the European Union (EU), have encountered a substantially sharper increase than others.

Tuomilehto brought up the World Health Organization's Diabetes Mondiale (DiaMond) study that aimed to assess the global incidence of diabetes. This massive, multi-center undertaking currently features 33,718 cases of T1DM with 443,499,882 person-years of follow-up. Of the 189 centers enlisted within 71 countries, 106 centers have provided data. Projecting a global map, Tuomilehto indicated that the incidences of T1DM were found to be among the highest in North America (Canada, moreso than the US) and in the EU - Finland, for example, encounters upwards of 50 new cases of T1DM per 100,000 person annually. On the other end of the spectrum, Asian countries, such as Russia, Wuhan in China, and Sichuan in China, were identified as having among the lowest incidences, with 6.0, 4.6, and 2.3 new cases of T1DM per 100,000 persons annually, respectively. Between 1990 and 1994 in South America, he continued, Montevideo in Uruguay, Tierra del Fuego in Argentina, and San Paolo in Brazil experienced 8.3, 8.0, and 8.0 new cases of T1DM per 100,000 persons annually, respectively. Alarmingly, the annual incidences of T1DM in North America, Asia, and South America have increased by 5.3%, 4%, and 5.3% every year between 1990 and 1999.

A number of reasons may explain the low, but often variable, incidences of T1DM in certain countries, such as low genetic susceptibility (ie, East Asians). The low prevalences of T1DM in low- and middle-income countries may be explained by factors that include the quality of diabetes care, survival, and reproduction and fertility rates. For instance, inaccessible and/or unaffordable healthcare that may result in the misdiagnoses or lack of diagnoses of T1DM. Consequent poor glycemic control and high rates of complications may result in high mortality among persons with T1DM and may also reduce reproduction rate.

While some international variations do exist, there were several general epidemiological trends for T1DM worth noting: 1) The incidence rates of T1DM diagnosed in children ages 14 or under are increasing; 2) More females than males have T1DM in low-incidence countries, but more males than females have T1DM in high-incidence countries; and 3) Overall, the incidence of T1DM appear to be higher in well-developed and high-income countries than in low- and middle-income countries. Fortunately, there is a light at the end of the tunnel, and with advances in medicine, improved research initiatives, and increased awareness and education, survival rates for patients with T1DM has continued to improve over the years.