Type 2 diabetes is characterized by insulin resistance, impaired insulin secretion and hyperglycemia. The pathophysiology is multifactorial with involvement of both genetic and lifestyle/environmental factors. Optimal glycemic control is the treatment goal in patients with type 2 diabetes, since the risk of long-term complications is associated with poor control.
Despite the availability of several oral anti-diabetic drugs and insulin, less than one third of patients with type 2 diabetes achieve the recommended target levels. With the increasing incidence and prevalence of type 2 diabetes, there is a significant unmet medical need for treatment alternatives with improved efficiency and safety.
According to the U.S. Centers for Disease Control and Prevention (CDC), a total of 23.6 million Americans had diabetes in the year 2007, two-thirds of whom are diagnosed and one-third of whom are not. Another 57 million have impaired fasting glucose (IFG or prediabetes), placing them at significant risk of progressing to type 2 diabetes. In the U.S. alone, 1.6 million new cases of diabetes were diagnosed in people aged 20 years or more in the year 2007 (National diabetes fact sheet: General information and national estimates on diabetes in the United States, 2007 (U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 2008)). A study using data from the National Health Interview survey estimated the lifetime risk of developing diabetes for individuals born in 2000 is 32.8% for males and 38.5% for females. The highest estimated lifetime risk for diabetes is among Hispanics. The CDC predicts that by the year 2050, there will be 48.3 million people with diagnosed diabetes in the U.S., an increase of 198% from the year 2005.
Worldwide figures are even more staggering: the World Health Organization reports a worldwide prevalence of 217 million persons with diabetes in the year 2005. While new cases of heart disease and cancer are stable or decreasing, the incidence of diabetes has increased 6% annually in the United States, and more so in developing countries. Furthermore, the disease shows no signs of abating. WHO predicts that by the year 2030, there will be at least 366 million people with diabetes. More than 90% of diabetic patients are classified as type 2, a fact that is directly related to aging, unhealthy diet, obesity and sedentary lifestyles.
Diabetes exhibits dramatic geographic and ethnic variation. Scandinavia and the Mediterranean island of Sardinia have the highest incidence rates in the world, whereas China, Japan and Korea have the lowest rates. The prevalence of diabetes is higher in developed than in developing countries, although the rate is increasing faster in developing countries; by 2025, there will be a 70% increase in the number of people with diabetes in developing countries compared with 42% in developed countries. In Southeast Asia alone, there will be an estimated 119 million people with diabetes by 2030, according to WHO. Although the majority of people with diabetes in developed countries are aged over 64 years, those in developing regions, such as Southeast Asia, are aged between 45 and 64 years.
The prevalence of diabetes increases steadily with age. Among the under-20 age group only 0.19% of all people have diabetes. In the 20 and older age group, the prevalence increases to 8.6% and for those aged 65 years and older, the figure is 20.1%. The annual incidence of diabetes among U.S. subjects aged 65 years and older increased by 23% in the decade between 1994-1995 and 2003-2004. The prevalence of diabetes in that population increased in the same period by 62%.
The prevalence of diabetes is currently higher in developed countries than in the developing world, and is expected to remain so for the next 25 years. However, during the period 1995-2025 the prevalence of adult diabetes in developing countries is predicted to increase by an astonishing 170%, compared to an increase of 41% in the developed world over the same time period. Furthermore, whereas most patients with diabetes in developed countries will be 65 years of age or older by 2025, most of those in the developing world will be in the 45-64 year age range, with the result that some of their most productive years will be compromised by the disease.
Because of its chronic nature, the severity of its complications and the means required to control them, the cost of diabetes is disproportionately high. The types of costs related to diabetes include the direct medical/healthcare costs of treating persons with diabetes and the indirect expenditures related to premature disability, premature death, lost workdays, restricted activity and sickness absence. The WHO estimates that 2.5-15% of annual health budgets are spent on diabetes-related illnesses. In the U.S. alone, diabetes cost an estimated USD $174 billion in 2007, including USD $116 billion in excess medical expenditures and USD $58 billion in lost productivity. This figure for healthcare spending is more than double what the spending would be without diabetes. Per capita medical expenditures totaled USD $13,243 for persons with diabetes compared with USD $2,560 for those without diabetes. With the rising prevalence of diabetes, associated costs will also skyrocket in the coming years and decades: the American Diabetes Association projects that total diabetes-related costs will reach USD $156 billion in 2010, and will be as much as USD $192 billion in 2020.
As high as these numbers are, the estimated cost of diabetes is most likely underestimated as it does not account for pain and suffering, care provided by non-paid caregivers, and several areas of healthcare spending where persons with diabetes probably use services, such as dental and optometry care, at a higher rate than those without diabetes. Predicting the use and costs of health services by persons with diabetes remains a challenge.