Manifestations and Epidemiology of Diabetes Mellitus

Diabetes mellitus is a group of diseases that is characterized by high levels of blood glucose (hyperglycemia). The high glucose levels can result from defects in insulin production, insulin action, or both. This hyperglycemia may be caused by a deficiency of insulin secretion due to pancreatic beta cell dysfunction and/or insulin resistance in the liver and muscle. Diabetes potentially can lead to serious complications including damage to the heart, eyes, kidneys, nerves and vascular system, but there are strategies to control the disease and reduce the risk of complications. Universal simplified terminology of the diabetes classifications occurred in 1997 by consensus of the American Diabetes Association and The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Diabetes classification is no longer based on the treatment or age at onset.1

Type 1 diabetes or insulin-dependent diabetes mellitus (IDDM), previously referred to as juvenile-onset diabetes, develops when the body’s immune system destroys pancreatic beta cells, the only cells in the body that make the hormone insulin that regulates blood glucose.1 Type 1 diabetes usually occurs in children and young adults, although its onset can occur at any age. It may account for about 5% of the diagnosed cases of diabetes.2,3,55 Risk factors for type 1 diabetes may include autoimmune, genetic, and environmental factors.

Type 2 diabetes or non-insulin-dependent diabetes mellitus (NIDDM), previously referred to adult-onset diabetes, may account for approximately 90% to 95% of all diagnosed cases of diabetes.2,3 It usually begins as insulin resistance, a disorder in which the cells do not use insulin properly. As the need for insulin rises, the pancreas gradually loses its ability to produce insulin. Type 2 diabetes is associated with increased age, obesity, family history of diabetes, history of gestational diabetes, impaired glucose metabolism, physical inactivity, and race/ethnicity. For example, African Americans, Hispanic/Latino Americans, American Indians, and some Asian Americans and Native Hawaiians or Other Pacific Islanders have a particularly high risk for type 2 diabetes. Its incidence is increasing in children and adolescents.2-4

Gestational diabetes is a form of glucose intolerance that can occur during pregnancy. Gestational diabetes occurs in approximately 4% of all pregnancies in the United States, but it is diagnosed more frequently among African Americans, Hispanic/Latino Americans, and American Indians. It is also more common among obese women and women with a family history of diabetes.2,3 During pregnancy, gestational diabetes requires treatment to avoid complications in the infant. After pregnancy, 5% to 10% of women with gestational diabetes are found to have type 2 diabetes.4 Women who have had gestational diabetes have a 20% to 50% chance of developing diabetes in the next 5-10 years.4

Other specific types of diabetes result from specific genetic conditions (such as maturity-onset diabetes of youth), surgery, drugs, malnutrition, infections, pancreatic diseases,55 and other illnesses. Such types of diabetes may account for 1% to 5% of all diagnosed cases of diabetes.4