In diabetes the body can convert food to glucose, but there is a problem with insulin. In one type of diabetes (type 1) the pancreas does not manufacture enough insulin, and in another type (type 2) the body has insulin but cannot use the insulin effectively (called insulin resistance). When insulin is either absent or ineffective, glucose cannot get into the cells to be used for energy. Instead, the unused glucose builds up in the bloodstream and circulates through the kidneys. If a person's blood glucose level becomes high enough, the excess glucose "spills" over into the urine, causing frequent urination. This, in turn, leads to an increased feeling of thirst as the body tries to compensate for the fluid lost through urination.
Because diabetes deprives body cells of the glucose needed to function properly, several complications can develop to threaten the lives of diabetics further. The healing process of the body is slowed or impaired, and the risk of infection increases. Complications of diabetes include: higher risk and rates of heart disease; circulatory problems, especially in the legs, which often are severe enough to require surgery or even amputation; diabetic retinopathy, a condition that can cause blindness; kidney disease that may require dialysis; dental problems; and problems with pregnancy. Close attention to preventive health care such as regular eye, dental, and foot examinations and tight control of blood sugar levels have been shown to prevent some of the consequences of diabetes.
According to the NIDDK, more than 80% of people with type 2 diabetes are overweight, and in persons prone to type 2 diabetes, becoming overweight can trigger onset of the disease. It is not known precisely how overweight contributes to causation of this disease. One hypothesis is that being overweight causes cells to change, making them less effective at using sugar from the blood. This then stresses the cells that produce insulin, causing them gradually to fail. Maintaining a healthy weight and keeping physically fit can usually prevent or delay the onset of type 2 diabetes.
The relatively recent rise in type 2 diabetes in the United States is in part attributed to rising obesity among adults as well as overweight among children and adolescents. A CDC study (http://www.cdc.gov/mmwr/PDF/wk/mm5345.pdf) found that 54.8% of diabetics over age nineteen were obese between 1999 and 2002 compared with 45.7% in the same age group between 1988 and 1994. When the category was expanded to include diabetics who were obese or overweight, the percentage escalated to 85.2% in 1999–2002 compared with 78.5% in the earlier period.
Types of Diabetes
Non-insulin-dependent diabetes (type 2) is most often seen in adults and is the most common type of diabetes in the United States. In this type the pancreas produces insulin, but it is not used effectively and the body resists responding to it.
The individuals most at risk for type 2 diabetes are usually overweight, are older than age forty, and have a family history of diabetes. According to the American Diabetes Association (http://www.diabetes.org/), patients with type 2 diabetes represent about 90-95% of patients with diabetes. Type 1 accounts for only about 5-10% of diabetes cases.
To determine whether someone has prediabetes or diabetes, a fasting plasma glucose (FPG) test or an oral glucose tolerance test (OGTT) is done in the doctor's office. A fasting blood glucose level between 100 and 125 mg/dl signals prediabetes, and a fasting blood glucose level of 126 mg/dl or higher signals diabetes. With the OGTT test, a patient fasts overnight, then drinks a solution rich in glucose. The patient's blood glucose level is then measured at one-hour intervals, commonly over two to five hours, to determine the rate at which the glucose is consumed. A diagnosis of prediabetes is made when the two-hour blood glucose level is between 140 and 199 mg/dl, and diabetes is diagnosed when the level is 200 mg/dl or higher.
Warning Signs of Diabetes
The symptoms of type 1 diabetes usually occur suddenly. These include excessive thirst, frequent urination, weight loss, weakness and fatigue, nausea and vomiting, and irritability. The symptoms of type 2 diabetes generally appear gradually. These may include any of the symptoms seen in type 1 diabetes, plus recurring infections that are slow to heal, drowsiness, blurred vision, numbness in the hands or feet, and itching.
Prevalence of Diabetes
The NHIS found that from 1997 through June 2005 there was an increase in diagnosed diabetes among U.S. adults. In 2005 more than 7% of the U.S adult population had been diagnosed with diabetes by a physician or other health professional. (See Figure 5.26.) Worse still, these numbers may significantly underestimate the true prevalence of diabetes in the United States in view of the findings of the National Health and Nutrition Examination Survey (conducted by the National Center for Health Statistics, a division of the CDC) that showed sizeable numbers of adults have undiagnosed diabetes.
The prevalence of diabetes increases with age among men and women, with the highest rates among older adults—persons age sixty-five and older. In all age categories the prevalence of diagnosed diabetes was higher in men than women. (See Figure 5.27.) The CDC also reports (http://www.cdc.gov/nchs/data/nhis/earlyrelease/200512_14.pdf) that the prevalence of diagnosed diabetes was higher among non-Hispanic African-Americans (10.9%) and Hispanic persons (9.2%) than among non-Hispanic whites (6.3%).
Causes of Diabetes
The causes of both type 1 and type 2 diabetes are unknown, but a family history of diabetes increases the
FIGURE 5.26 Prevalence of diagnosed diabetes among adults aged 18 years and over, 1997–2005
In type 2 diabetes heredity may be a factor, but because the pancreas continues to produce insulin, the disease is considered more of a problem of insulin resistance, in which the body is not using the hormone efficiently. In people prone to type 2 diabetes, being overweight can set off the disease because excess fat prevents insulin from working correctly. Maintaining a healthy weight and keeping physically fit usually can prevent type 2 diabetes. To date, type 1 diabetes cannot be prevented.
Inhaled Insulin Is Newest Diabetes Treatment
On January 27, 2005, the FDA approved Exubera, the first short-acting insulin via an inhaler. Although use of rapid-acting inhaled insulin will not replace the need to occasionally inject the hormone, it offers many adults with type 2 diabetes an alternative to the frequent insulin injections necessary to control their blood sugar.
FIGURE 5.27 Prevalence of diagnosed diabetes among adults aged 18 years and over, by age group and sex, January-June 2005
"Diabesity" and "Double Diabetes"
Recognition of obesity-dependent diabetes prompted scientists and physicians to coin a new term to describe this condition—diabesity. The term was first used in the 1990s, and it has gained widespread acceptance. Although diabesity is attributed to the same causes as type 2 diabetes—insulin resistance and pancreatic cell dysfunction—researchers are beginning to link the inflammation associated with obesity to the development of diabetes and cardiovascular disease.
Pediatric endocrinologist Francine R. Kaufman M.D., who served as president of the American Diabetes Association, contends that the diabesity epidemic "imperils human existence as we now know it" in Diabesity: The Obesity-Diabetes Epidemic That Threatens America—And What We Must Do to Stop It (New York: Bantam, 2005) and observes that more than one-third of American children born in 2000 will develop diabetes in their lifetime. Dr. Kaufman warns that unless drastic measures are taken, by 2020 there will be a 72% increase in the number of diabetics in America.
Another recent phenomenon is patients diagnosed with both type 1 and type 2 diabetes simultaneously. Dubbed "double diabetes," it has been reported in children and adults. Among children, it often results when children with type 1 diabetes who rely on insulin injections to control their diabetes gain weight and develop the insulin resistance that characterizes type 2 diabetes. Adults who have been diagnosed with type 2 diabetes but fail to respond to treatment have been found to also suffer from the type 1, the insulin-dependent form of the disease.
Although there are no reliable statistics about the prevalence of double diabetes, in a July 19, 2005, interview Dr. Dorothy Becker, a pediatric endocrinologist and leading double-diabetes researcher at Children's Hospital of Pittsburgh, estimated that 25% of children with type 1 diabetes who are overweight also have symptoms of type 2 diabetes. Dr. Becker theorizes that overweight people require more insulin to process glucose regardless of whether they are insulin-resistant. It may be that obesity overworks the pancreas until it wears out. It also is possible that obesity triggers or hastens the autoimmune destruction, which implies that individuals genetically predisposed to type 1 diabetes might not develop the disease if they maintained a healthy weight (Lauran Neergaard, "'Double Diabetes' Harder to Detect, Treat," Associated Press, July 19, 2005).
Deaths Resulting from Diabetes
The risk for death among people with diabetes is about twice that of their age peers without diabetes. Diabetes was the sixth-leading cause of death in the United States in 2003 and was responsible for more than seventy-four thousand deaths. (See Table 5.4.) The NIDDK asserts that diabetes is likely to be underreported as a cause of death. The institute reports that only about 35-40% of the deceased with diabetes had diabetes listed on their death certificates and just 10-15% had it listed as the underlying cause of death.
TABLE 5.10 Selected chronic health conditions causing limitation of activity among working-age adults by age, 2002–03
| TABLE 5.10 | |||
|---|---|---|---|
| Selected chronic health conditions causing limitation of activity among working-age adults by age, 2002–03 | |||
| Type of chronic health condition | 18-44 years rate* | 45-54 years rate* | 55-64 years rate* |
| *Rate = Number of persons with limitation of activity caused by selected chronic health conditions per 1,000 population. | |||
| Notes: Data are for the civilian noninstitutionalized population. Conditions refer to response categories in the National Health Interview Survey (NHIS); some conditions include several response categories. "Mental illness" includes depression, anxiety or emotional problem, and other mental conditions. "Heart or other circulatory" includes heart problem, stroke problem, hypertension or high blood pressure, and other circulatory system conditions. "Arthritis or other musculoskeletal" includes arthritis or rheumatism, back or neck problem, and other musculoskeletal system conditions. Persons may report more than one chronic health condition as the cause of their activity limitation. | |||
| SOURCE: "Data Table for Figure 19. Selected Chronic Health Conditions Causing Limitation of Activity among Working-Age Adults by Age: United States, 2002–03," in Health, United States, 2005, Centers for Disease Control and Prevention, National Center for Health Statistics, November 2005, http://www.cdc.gov/nchs/data/hus/hus05.pdf (accessed January 3, 2006) | |||
| Mental illness | 12.9 | 23.1 | 24.1 |
| Fractures or joint injury | 7.0 | 15.5 | 20.6 |
| Lung | 5.0 | 12.6 | 25.6 |
| Diabetes | 2.5 | 13.4 | 33.4 |
| Heart or other circulatory | 5.9 | 28.4 | 74.3 |
| Arthritis or other musculoskeletal | 22.2 | 61.9 | 100.7 |
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