Diabetes mellitus is a chronic, metabolic disease defined by increased concentrations of blood glucose which leads, over time, to progressive damage in most tissues and organs including the heart, blood vessels, eyes, kidneys, skin, and nerves. The most common is type 2 diabetes, commonly in adults, which occurs as a result of the combination of insulin resistance with pancreatic beta-cell insufficiency, with 50% of patients requiring insulin treatment within 10 years. Type 1 diabetes, more frequent in children and adolescents, is a chronic autoimmune disease in which autoreactive T lymphocytes and inflammation cause severe loss of beta cells. The incidence of diabetes exhibits an alarming pandemic scenario, in large part due to the global obesity epidemic. Diabetes causes premature death, severe disability, and a great economic burden. Therefore, there is a globally agreed target to stop the growing incidence of
1 Epidemiology of Diabetes diabetes and obesity by 2025.
The number of adults living with diabetes has approximately quadrupled from 1980 (108 million) to 2014 (422 million). The age-standardized prevalence of diabetes has nearly doubled since 1980, increasing from 4.7 to 8.5% in the adult population. This is consequent to a rise in associated risk factors such as
sedentary lifestyle, greater longevity, poor eating habits (high in salt, low in fiber, and rich in saturated fats and sugar), and, especially, overweight/obesity. Indeed, the obesity pandemic explains a large part of the global epidemic of diabetes (especially type 2 diabetes). In 2014, global estimates showed that more than one in three adults aged over 18 years were overweight (body mass index, BMI 25–29.9 kg/m2), and 10% were obese (BMI ≥30.0 kg/m2 ). Both overweight and obesity were higher in women than men, lowest in the WHO South-East Asian region, and highest in the WHO Region of the Americas. Moreover, the prevalence of overweight/obesity rises with country income level. Physical inactivity is more common in women (27%) than men (20%) across all country income groups from all WHO regions, and is more common among adolescents (78% of boys, and 84% of girls), especially from high-income countries.
In the last decade, diabetes prevalence, in a pandemic scenario, has increased less fast in high-income nations than in low- and middle-income countries, including Africa and Asia, where most diabetic patients will probably be found by 2030. This rising incidence of diabetes in developing countries accompanies the trend of unhealthy lifestyle changes (low physical activity and Western pattern eating habits) and urbanization. The WHO Eastern Mediterranean region has shown the highest increases in diabetes prevalence and nowadays exhibits the highest prevalence (13.7%). Of note, the risk of type 2 diabetes is strongly associated with lower socioeconomic status.
Diabetes generated approximately 1.5 million deaths in 2012. In addition, suboptimal high blood glucose caused 2.2 million deaths, by increasing the risks of heart disease and other associated conditions such as kidney failure, stroke, and tuberculosis. Forty-three percent of these 3.7 million deaths arise before the age of 70 years. The percentage of deaths secondary to hyperglycemia or diabetes that appear prior to age 70 is greater in low- and middle-income countries than in high-income countries. In 2012, diabetes was the eighth leading cause of death among both sexes and the fifth leading cause of death in women 2012.
Importantly, separate global estimates of diabetes prevalence for type 1 and type 2 do not exist. Approximately, 85% of people with diabetes, mostly adults and elderly people, are affected by type 2 diabetes. Unfortunately, in the last decade, there is also a rising incidence of type 2 in children, especially in children of ethnic minorities and from lower-income families. Type 2 diabetes is frequently undiagnosed; therefore there are almost no data about its true incidence. Recently, it was reported that between 24 and 62% of diabetic patients from seven countries were undiagnosed and untreated. A high proportion of undiagnosed diabetes can be found even among individuals from high-income countries. Even though the prevalence of type 2 is frequently highest in wealthy subjects, this trend is changing in some middle-income countries. In addition, in high-income populations, type 2 diabetes is highest among individuals
who are poor.
Type 1 diabetes occurs, especially in children and adolescents. Most evidence about the incidence of type 1 diabetes has been obtained from population-based registries of new cases worldwide, such as the WHO DIAMOND project. These registries reported large differences in the incidence of type 1 diabetes, ranging from under 0.5 to over 60 cases annually per 100,000 children (under 15 years). According to the WHO DIAMOND project, Scandinavia, Sardinia and Kuwait exhibit the highest incidence for type 1 diabetes, while is much less common in Asia and Latin American. The worldwide epidemiology of type 1 diabetes shows a pandemic scenario with an annual increase of ~3%, especially in children from high-income countries.