Diabetes mellitus is a complex, chronic metabolic disorder characterized by an imbalance of availability and/or function of insulin within the body, which results in elevated levels of glucose (sugar) in the bloodstream. The most prevalent form of diabetes, “late-onset” or “type 2,” accounts for 90 to 95 percent of all cases worldwide. It tends to affect adults whose genetic makeup and/or lifestyle have caused them to lose the ability to produce insulin or, more commonly, to utilize the insulin produced appropriately. Type 1 diabetes is characterized by autoimmune destruction of the pancreas's beta cells, which secrete insulin, and tends to affect younger people, requiring use of insulin injections to supplement their needs.
Both types of diabetes are associated with acute and chronic complications. The occurrence of these disabling and often life-threatening complications varies widely, depending on the individual's susceptibility, the duration of diabetes, and how well glucose and other vascular risk factors (blood pressure, cholesterol) are controlled. Acute fluctuations in glucose (hyperglycemia, too high, or hypoglycemia, too low) tend to occur more often in insulin-treated people and require urgent responses; they are potentially fatal if untreated. In terms of chronic complications, diabetes can cause or contribute to the emergence of cardiovascular disease (coronary heart disease, strokes, and heart failure), eye diseases (cataracts, retinopathy), chronic kidney disease and failure, and nerve/vascular disease (sometimes leading to foot ulcers and amputation). In addition, diabetes predisposes sufferers to other cardio-metabolic risk factors such as high blood pressure, abnormal cholesterol levels, and inflammatory conditions. These, in turn, increase the risk of organ-damaging complications.
In addition to having a dramatic impact on sufferers' quality of life, diabetes is a leading cause of death worldwide, accounting for 4.6 million deaths annually, far outnumbering the combined global deaths due to HIV/AIDS, malaria, and tuberculosis. The condition also exacts a very high economic and social cost from individuals, families, and communities.
Diabetes has affected human beings for thousands of years; the first documented references to the disease's prime symptom—namely excessive urination, or polyuria—date to 1500 B.C.E. As ancient societies lacked the ability to measure blood sugar, the earliest descriptions of the condition simply depict changes in urine output as well as the resulting fatalities. The term “diabetes” was first introduced in the first or second century B.C.E., derived from Ionic and Latin terms meaning “to pass through” or “to siphon.”
The first means for detecting diabetes—tasting the urine for excessive sweetness—was used by the Egyptians, Indians, and Asians for millennia. It was not until 1841 that a chemical test for excess glucose in urine (glycosuria) was developed. That was followed in 1850 by a test that quantified the precise amount of sugar excreted in urine, and eventually by tests that measured the glucose content of blood.
Since the early 1970s, diagnosis of diabetes has been accomplished by measuring blood glucose levels in standardized ways—either by having a patient fast for an extended period of time (usually 8–12 hours) or by administering an oral glucose challenge (the patient drinks 75 grams of glucose and has the blood tested after two hours). There has been much debate over the appropriate cutoff values for the diagnosis of diabetes and/or pre-diabetes, however, and the generally accepted values have changed a number of times in the past several decades.
For example, the National Diabetes Data Group in 1979 and the World Health Organization (WHO) in 1980 established thresholds for diabetes diagnosis that stood for nearly 20 years, while also dividing sufferers into two groups: those with impaired glucose tolerance (IGT, a form of pre-diabetes where sugar levels are high, but not quite in diabetes range) and those with full-fledged diabetes. Diabetes was further divided into three types: insulin-dependent diabetes mellitus, non-insulin-dependent diabetes, and gestational diabetes. Another major update in 1997–1998 lowered the diagnostic cutoff values, defined a new entity called impaired fasting glucose (IFG, another form of pre-diabetes), and adopted new category names—type 1, type 2, gestational, and “other” forms of diabetes.
Given that glucose tolerance tests are often impractical, due to their cost and the time they take to administer, the primary means of testing has been based on fasting plasma glucose levels. More recently, the American Diabetes Association (ADA) has introduced a nonfasting test that measures longer-term blood glucose levels (called glycosylated hemoglobin) as a means of diagnosing the disorder.
Just as the tools and criteria for diagnosing diabetes have evolved rapidly in the past century, so too has the understanding of the disease and the strategies for treating it. The link between the types of food a person consumes and the amount of sugar in their urine was noted in the nineteenth century. As such, the primary treatment for diabetes at that time—indeed, the only treatment—was dietary modification. Sufferers would be instructed to eliminate certain foods from their diets—mainly sugars—and to reduce overall food intake, sometimes to as little as 500 calories per day. This was helpful, but only moderately so, extending lives by no more than a year or two.
In 1921, the surgeon Frederick Banting and his assistant Charles Best revolutionized the treatment of diabetes. The two men experimented on a severely diabetic dog, injecting him with cells extracted from a canine pancreas. As these cells tend to clump together to form “islands” within the pancreas, they were given the name “insulin” (from the Latin insula, or island) in the 1860s. The insulin treatment was a success, and the life of the dog was extended for 70 days. Banting and Best followed by injecting the extract into a young diabetic named Leonard Thompson. Thompson had been given less than a year to live, but within 24 hours of the injection, his blood sugar had dropped to a normal level. For the first time, a diagnosis of diabetes was no longer a de facto death sentence. In recognition of his work, Banting was awarded a Nobel Prize in 1923.
Since then, large-scale studies have afforded insight into many aspects of diabetes, including the risk factors that lead to it, the progression of the disease, and burdens in diverse populations around the globe. These studies have also clarified the social and environmental triggers of type 1 diabetes (viral infections) and type 2 diabetes (mainly age, family history, physical inactivity, and dietary choices). While the molecular and biochemical mechanisms underlying type 1 and 2 diabetes are still not fully understood, successive waves of studies have identified some of the genes associated with occurrence of diabetes.
As people with type 1 diabetes are deficient in insulin, treatment is primarily done through insulin supplementation. Early forms of insulin were animal-derived (bovine or porcine), while contemporary forms are human or synthetic. A landmark study, the Diabetes Control and Complications Trial, conclusively demonstrated that early and intensive blood glucose control in people with type 1 diabetes prevents—or at least substantially delays—cardiac, eye, nerve, and kidney complications.
For type 2 diabetes, treatments include lifestyle modification, a number of medications (with different mechanisms of action), and injectable insulin. Metformin, the first drug developed to combat diabetes, remains the first-line drug Page 257 | Top of Articleof choice. The United Kingdom Diabetes Prospective Study, another landmark effort, revolutionized our understanding of type 2 diabetes management, creating a shift from a pure focus on glucose levels to controlling multiple risk factors (blood pressure, glucose, avoidance of tobacco use, and so forth).
For proper management of all forms of diabetes, it is important that sufferers regularly check their blood glucose levels. In decades past, this was done with urine tests. These were suboptimal, however, for two reasons. First, they can identify high levels of glucose, but not dangerously low levels. Second, they reflect hours-old—and not current—glucose levels. In 1976, physicians developed a means of measuring blood sugar by testing the hemoglobin A1C in the blood. This remains the standard tool for daily measurement, with patients using handheld glucose meters and a small drop of blood taken by pin-prick from the finger to check glucose before and after insulin doses or meals.
The application of epidemiology (the study of the distribution and causes of diseases) to diabetes has had an important role in quantifying the impact of the condition, identifying risks factors that might be addressed, informing resource allocation and policy, and monitoring the effects of interventions. However, the data regarding chronic diseases in general, and diabetes in particular, have been limited in many regions of the world, particularly in low-resource settings. Available data are derived from ad hoc studies that have used heterogeneous methods and surveyed people who are not always representative of their national populations. As a result, the data are not easily comparable.
To understand the distribution and magnitude of diabetes globally, WHO and the International Diabetes Federation have relied on sophisticated methods that combine available country data and extrapolate estimates for the remaining countries without data. They estimate that between 347 million and 366 million adults worldwide are affected by diabetes, and that the burden of diabetes has grown since the early 1980s. The growth of type 2 diabetes over recent decades is spurred on by major global transitions, namely the demographic (e.g., population aging), socioeconomic (e.g., growth of the middle class in emerging economies), and lifestyle (changing diet and physical activity patterns) transitions that continue to occur worldwide.
It is estimated that two-thirds of those affected by diabetes live in low-and middle-income countries (LMIC). In fact, of the 10 countries with the highest number of diabetes sufferers (China, India, United States, Russia, Brazil, Japan, Mexico, Bangladesh, Egypt, and Indonesia), eight are developing or transitioning-economy countries. This challenges the traditional notion that chronic diseases such as diabetes are largely the problem of affluent countries and populations. To date, LMICs have justifiably focused their attentions on infectious disease and nutritional deficiency burdens. However, these same countries must now also contend with chronic diseases, thus facing a so-called double burden of disease.
Diabetes is also a “silent epidemic,” as it progresses slowly and does not have any palpable symptoms in its early stages. Without symptoms or a test result showing high blood sugar, people who are affected may not be aware of their risk and might not perceive a need to seek medical attention and preventative care. As a result, estimates of the number of diabetes sufferers may understate the true number, as these “undiagnosed cases” account for between 30 and 50 percent of all diabetes cases, even in the most advanced countries.
Although there is some variation among regions, there is no region of the world where diabetes is not a major public health concern. In Africa, diabetes prevalence over the past two decades has varied between 1 and 3 percent in rural areas and 6 and 10 percent in urban environments. Similar figures (1.2–8 percent) were noted for Latin America over the same period. However, for both these regions, the estimates may be an underrepresentation, as diagnosis tends not to occur until complications have developed late in the course of the disease. In Asia, a number of populous countries (India, China, and Indonesia) are home to very high absolute numbers of people with diabetes. Data from Malaysia, Thailand, Japan, the Philippines, Taiwan, and Hong Kong indicate an 8 to 12 percent prevalence of diabetes. Meanwhile, roughly 10 percent of the residents of Western Europe and high-income North America have diabetes, and both regions have observed significant growth of both Page 258 | Top of Articletype 1 diabetes and type 2 diabetes in the past two decades, particularly among elderly, disadvantaged, and ethnic minority subpopulations.
Different racial and ethnic groups also exhibit different diabetes risk patterns. Middle Eastern and Pacific Islander populations have the highest prevalence of diabetes—primarily type 2—worldwide. Asian Indians and black African populations (primarily those living in high-income countries, such as African Americans) also have an elevated risk. Type 1 diabetes has been more commonly documented in populations of Caucasian origin than in other racial/ethnic groups.
There are notable differences in diabetes prevalence between rural and urban environments. Studies of the disease have predominantly focused on urban populations and traditionally show two to three times greater prevalence for urban as compared with rural populations (e.g., 10–15 percent versus 5 percent). However, evidence suggests that diabetes prevalence is growing in both settings. Systematic reviews of studies that focused on diabetes in rural inhabitants show dramatic increases over the past two to three decades. This growth of diabetes in rural areas may reflect either alteration in lifestyle choices (moving away from traditional and physical rural occupations, consuming more refined/processed diets) or increased selective urbanization (younger people relocate to cities, resulting in smaller, older, more diabetes-prone rural populations).
Traditionally, diabetes was viewed as a disease that affected the more well-to-do segments of society. However, recent studies in higher-income countries have consistently documented a higher risk for diabetes among people of lower socioeconomic classes. In LMICs, the greatest risk of diabetes is still observed among people of higher socioeconomic class, although evidence suggests that the disease is becoming much more prevalent in poorer communities.
A variety of factors may be driving this phenomenon, many of them common to both high-and low-income countries. For example, aspirations to move up the socioeconomic ladder affect how people perceive mechanization of transport—that is to say, people who once walked or ran are now driving or riding, which means they are getting less exercise. Such aspirations can affect dietary choices, as processed foods are viewed as symbols of status and luxury among poorer classes. Limited awareness and constrained purchasing power serve to perpetuate these trends, as calorie-and fat-dense processed foods become more available and financially accessible.
One in four people with diabetes suffers from some form of visual impairment, and 5 percent of all cases of blindness globally are due to diabetes. Approximately 45 percent of end-stage renal disease is associated with diabetes, and the risk of cardiovascular diseases (coronary disease, stroke, and heart failure) is two to four times higher in people with diabetes than those without. In addition to these physical impairments, diabetes is associated with “hidden disabilities” like psychological disturbances (e.g., depression) and impaired domestic and occupational functioning (e.g., work performance affected by impaired motor skills, frequent need to urinate, and grogginess). People with diabetes also have a higher rate of hospitalization.
Most significantly, diabetes results in a shorter life expectancy—approximately 7 to 15 years less on average. Cardiovascular disease is the predominant cause of death in people with diabetes in high-income countries, with the greatest proportion of deaths occurring after the age of 65. Meanwhile, infections and acute metabolic emergencies are the leading causes of death in low-resource settings, where younger age groups experience a substantial number of diabetes-related deaths. This results in higher loss of economically productive years in these regions. Availability of appropriate care and treatment are the primary determinants of these differences—for example, mortality from acute hyperglycemia is extremely low in high-income countries like the United States and Denmark (0.67–4.0 percent of cases) but can be as high as 25 to 33 percent in some African countries.
It is difficult to quantify the direct economic costs of diabetes—that is, the expenditures related to medical care and treatments—as different studies use widely varying methods. Estimates suggest that sufferers incur 1.5 to 5 times greater health-care expenses than the general nondiabetic population, depending on the context and pricing methods used. These costs increase with more co-morbidities, the conditions that often accompany diabetes and require treatment, such as hypertension (high blood pressure), and with more severe stages of the disease in which complications develop (e.g., heart disease) and the complexity of therapies all increase.
Unfortunately, vulnerable populations—particularly the elderly and the poor—are not only at elevated risk of diabetes, but also devote larger proportions of their resources toward care. At the micro level, this depletes household resources and diminishes the opportunities that could have otherwise been pursued. At a macro level, the morbidity and premature mortality experienced by those with diabetes are reflected in lost human and social capital for society. This affects economies of households, companies, communities, and whole countries.
The amount of direct spending on diabetes care varies widely among nations. Relatively few dollars are spent per year on each diabetic patient in less developed countries, like Tanzania (US $4 per patient) or South Africa (US $158). Wealthier countries spend more, though the figures still differ dramatically depending on demographics, available resources, and the structure of the nation's medical system. Argentina, for example, spends US$330 per diabetes sufferer, France $675, and Denmark $3,535.
In addition to these direct costs are other financial burdens that are all but impossible to quantify. Indirect costs refer to the value of economic productivity lost because of illness or premature mortality. Intangible costs refer to the psychosocial burdens—depression, loss of self-confidence, stress—imposed by a disease. Though a precise dollar figure cannot be calculated, diabetes surely exacts an enormous toll in these areas.
The health, economic, and psychosocial burdens of diabetes have grown significantly since the 1960s, and they are projected to continue growing globally in coming decades. More reliable and consistent data collection will aid in understanding the factors that perpetuate diabetes risk, the health and economic impacts of the disease, and the most appropriate timing and population segments to target for intervention. Activist groups, some of them national (the ADA), and some transnational (the International Diabetes Federation, WHO) are taking the lead in this area.
There are huge disparities in burdens, access to care, and expenditures related to diabetes. Eighty percent of the health-care expenditures on diabetes occur in the regions where only 20 percent of people with diabetes live. It is unfortunate that scarcity of resources results in greater disability and mortality. This is particularly concerning as the lost productivity perpetuates the challenges that LMICs face in trying to achieve better social and economic outcomes.
Given that the care and consequences of diabetes are burdensome and costly, intervening before onset of the disease may be a decisive turning point in addressing the global burdens of diabetes. Around the turn of the century, evidence from five countries emerged demonstrating the benefits of structured lifestyle programs in people at high risk for diabetes (those with pre-diabetes or those who are overweight with other risk factors). This evidence showed that controlling weight through consuming a healthier diet and exercising regularly prevented, or at least forestalled, onset of the disease. However, there is still a long road to travel in this regard, and there are a number of political, sociocultural, behavioral, and economic barriers to overcome in trying to translate the evidence from prevention studies into real-life settings. Context-specific studies that are able to demonstrate sustainable and cost-effective benefits of diabetes prevention will be important. In addition, in increasingly lean times, it is important to evaluate the effects of large-scale population-focused interventions and policies so that the more beneficial can be sustained, while the least effective and efficient can be discontinued.
Together, evidence, resource investments, affordable and organized health care, and political will are required to translate what we know about diabetes into practical and accessible services, and to increase awareness such that those at risk or already affected by diabetes can be connected with the resources and services they need to remain healthy and preserve their quality of life.
Mohammed K. Ali, Justin B. Echouffo-Tcheugui, and K.M. Venkat Narayan
“Diabetic Creed” (excerpt), Elliot P. Joslin, 1923
A pioneer in diabetes research and treatment, Dr. Elliot P. Joslin was the first American doctor to specialize in the disease, the first to study its epidemiology, and a great proponent of the notion that controlling blood sugar through diet, exercise, regular testing, and treatment can prevent complications and improve the lives of people with diabetes. The following statement is a brief excerpt from his “Diabetic Creed.”
Three horses draw the diabetic chariot and their names are diet, exercise, and insulin. In fact, all of us in our life's journey depend on the three, but seldom recognize the third although we often realize we are poor charioteers. Yet we fortunate ones have instinct to help us hold the reins, but the diabetic cannot trust his instincts as a guide, and in place of it must depend upon dieticians, nurses and doctors unless he understands his disease.
Source: Joslin Diabetes Center. www.joslin.org .
“Political Declaration of the High-Level Meeting of the General Assembly on the Prevention and Control of Non-communicable Diseases” (excerpt), 2011
In September 2011, the UN General Assembly held a high-level meeting on noncommunicable diseases (NCD) in New York. The meeting was a landmark international event in the field, one many hoped would provide an important stimulus for evolving the manner in which diabetes and NCDs are confronted. Significantly, the meeting resulted in a political declaration—excerpted below—that includes diabetes and NCDs as issues that affect socioeconomic development; that identifies access, availability, and affordability of medicines and technologies as a key issue; and that calls for systems to deliver care and social protection for people affected by these diseases.
We, Heads of State and Government and representatives of States and Governments, assembled at the United Nations from 19 to 20 September 2011, to address the prevention and control of non-communicable diseases worldwide, with a particular focus on developmental and other challenges and social and economic impacts, particularly for developing countries,
1. Acknowledge that the global burden and threat of non-communicable diseases constitutes one of the major challenges for development in the twenty-first century, which undermines social and economic development throughout the world, and threatens the achievement of internationally agreed development goals;
2. Recognize that non-communicable diseases are a threat to the economies of many Member States, and may lead to increasing inequalities between countries and populations;
3. Recognize the primary role and responsibility of Governments in responding to the challenge of non-communicable diseases and the essential need for the efforts and engagement of all sectors of society to generate effective responses for the prevention and control of non-communicable diseases;
4. Recognize also the important role of the international community and international cooperation in assisting Member States, particularly developing countries, in complementing national efforts to generate an effective response to non-communicable diseases;
5. Reaffirm the right of everyone to the enjoyment of the highest attainable standard of physical and mental health;
6. Recognize the urgent need for greater measures at global, regional and national levels to prevent and control non-communicable diseases in order to contribute to the full realization of the right of everyone to the highest attainable standard of physical and mental health…
14. Note with profound concern that, according to WHO, in 2008, an estimated 36 million of the 57 million global deaths were due to non-communicable diseases, principally cardiovascular diseases, cancers, chronic respiratory diseases and diabetes, including about 9 million before the age of 60, and that nearly 80 per cent of those deaths occurred in developing countries;
15. Note also with profound concern that non-communicable diseases are among the leading causes of preventable morbidity and of related disability;
16. Recognize further that communicable diseases, maternal and perinatal conditions and nutritional deficiencies are currently the most common causes of death in Africa, and note with concern the growing double burden of disease, including in Africa, caused by the rapidly rising incidence of non-communicable diseases, which are projected to become the most common causes of death by 2030;
17. Note further that there is a range of other non-communicable diseases and conditions, for which the risk factors and the need for preventive measures, screening, treatment and care are linked with the four most prominent non-communicable diseases;
20. Recognize that the most prominent non-communicable diseases are linked to common risk factors, namely tobacco use, harmful use of alcohol, an unhealthy diet, and lack of physical activity;
21. Recognize that the conditions in which people live and their lifestyles influence their health and quality of life, and that poverty, uneven distribution of wealth, lack of education, rapid urbanization and population ageing, and the economic social, gender, political, behavioural and environmental determinants of health are among the contributing factors to the rising incidence and prevalence of non-communicable diseases;
22. Note with grave concern the vicious cycle whereby non-communicable diseases and their risk factors worsen poverty, while poverty contributes to rising rates of non-communicable diseases, posing a threat to public health and economic and social development;
23. Note with concern that the rapidly growing magnitude of non-communicable diseases affects people of all ages, gender, race and income levels, and further that poor populations and those living in vulnerable situations, in particular in developing countries bear a disproportionate burden and that non-communicable diseases can affect women and men differently;
24. Note with concern the rising levels of obesity in different regions, particularly among children and youth, and note that obesity, an unhealthy diet and physical inactivity have strong linkages with the four main non-communicable diseases, and are associated with higher health costs and reduced productivity;
25. Express deep concern that women bear a disproportionate share of the burden of care-giving and that, in some populations, women tend to be less physically active than men, are more likely to be obese and are taking up smoking at alarming rates;
26. Note also with concern that maternal and child health is inextricably linked with non-communicable diseases and their risk factors, specifically as prenatal malnutrition and low birth weight create a predisposition to obesity, high blood pressure, heart disease and diabetes later in life; and that pregnancy conditions, such as maternal obesity and gestational diabetes, are associated with similar risks in both the mother and her offspring…
Source: United Nations.
Ali, Mohammed K., Mary Beth Weber, and K.M. Venkat Narayan. “Global Burdens of Diabetes.” In Textbook of Diabetes. 4th ed., ed. Richard I.G. Holt, Clive Cockram, Allan Flyvbjerg, and Barry J. Goldstein, 69–84. Hoboken, NJ: Wiley-Blackwell, 2010.
Economist Intelligence Unit. “The Silent Epidemic: An Economic Study of Diabetes in Developed and Developing Countries.” June 2007.
Hurley, Dan. Diabetes Rising: How a Rare Disease Became a Modern Pandemic, and What to Do About It. New York: Kaplan, 2009.
Kirchhof, Mark, Nooreen Popat, and Janet Malowany. “A Historical Perspective of the Diagnosis of Diabetes.” University of Western Ontario Medical Journal 78:1 (2008): 7–11.
McCarthy, Mark I. “Genomics, Type 2 Diabetes, and Obesity.” New England Journal of Medicine 363:24 (December 9, 2010): 2339–2350.
Narayan, K.M. Venkat, et al. “Diabetes: The Pandemic and Potential Solutions.” In Disease Control Priorities in Developing Countries. 2d ed., ed. Dean T. Jamison, Joel G. Breman, Anthony R. Measham, et al., 591–603. New York: Oxford University Press, 2006.
Narayan, K.M. Venkat, et al., eds. Diabetes Public Health: From Data to Policy. Oxford, UK: Oxford University Press, 2011.
Tattersall, Robert. Diabetes: The Biography. New York: Oxford University Press, 2009.
Zhang, Ping, et al. “Application of Economic Analysis to Diabetes and Diabetes Care.” Annals of Internal Medicine 140:11 (June 1, 2004): 972–977.
Zimmet, Paul. “Epidemiology of Diabetes—Its History in the Last 50 Years.” British Journal of Diabetes & Vascular Disease 2:6 (November 2002): 435–439.