Diabetes is a disease in which the body is unable to produce or properly use and store glucose, a form of sugar. Glucose backs up in the bloodstream, causing one's blood glucose (sometimes referred to as blood sugar) to rise too high.
There are two major types of diabetes. In type 1 (formerly called juvenile-onset or insulin-dependent) diabetes, the pancreas completely stops producing any insulin, a hormone that enables the body to use glucose found in foods for energy. People with type 1 diabetes must take daily insulin injections to survive. This form of diabetes usually develops in children or young adults but can occur at any age.
Type 2 (formerly called adult-onset or non-insulin-dependent) diabetes results when the body doesn't produce enough insulin or is unable to use insulin properly, a condition known as insulin resistance. This form of diabetes usually occurs in people who are over 40, overweight, and have a family history of diabetes, although today it is increasingly occurring in younger people, particularly adolescents.
According to federal statistics, an estimated 18.2 million children and adults in the United States-6.3 percent of the population-have diabetes. An estimated 13 million of these people have been diagnosed, and some 5.2 million are thought to have type 2 diabetes without knowing it. Most people with diabetes have type 2; an estimated 800,000 have type 1. Diabetes is the sixth-leading cause of death by disease in the United States. The condition and its complications cost an estimated $132 billion annually in the United States alone, in terms of healthcare expenses and lost productivity.
Poorly managed diabetes can lead to a host of long-term complications, including heart attacks, strokes, blindness, kidney failure, blood vessel disease that may require an amputation, nerve damage, and impotence in men. But a nationwide study completed over a 10-year period showed that if people keep their blood glucose level as close to normal as possible, they can reduce their risk of developing some of these complications by 50 percent or more.
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Your body changes much of the food you eat into glucose, a type of sugar, which is then carried by the bloodstream to be used to power the millions of cells in your body. The cells cannot use glucose for energy without the help of insulin, a hormone made by the pancreas that helps glucose enter them. Diabetes is a disease in which the body's insulin-producing system malfunctions. Glucose then builds up to excessive levels in the bloodstream.
In type 1 diabetes, which used to be called juvenile-onset or insulin-dependent diabetes, the body completely stops producing insulin. People with type 1 diabetes must take daily insulin injections to survive. This form of diabetes usually develops in children or young adults but can occur at any age. (In type 2 diabetes, which used to be called adult-onset or non-insulin-dependent diabetes, the body produces insulin but either does not produce enough to properly convert food into energy or is not able to use the insulin it does make. This form of diabetes usually occurs in overweight people who are over 40 with a family history of diabetes.)
In type 1 diabetes, the body stops-or almost stops-producing insulin because the immune system misfires and attacks the beta cells of the pancreas, which manufactures the hormone. The causes of this autoimmune disorder aren't known, although factors relating to genetics, environment, and trauma or infection all may be involved.
The possible risk factors for type 1 diabetes include some that are genetic, some that are environmental, and some that are related to trauma or infection. The interplay among factors is not entirely known.
Evidence suggests an environmental influence is at work in determining who gets type 1 diabetes, though the relationship is unclear. Among Caucasians, diabetes risk varies geographically. In general, the risk is higher in Northern Europeans than Southern Europeans-though Sardinians in the Mediterranean also are at elevated risk. In recent decades, there has been an upswing in type 1 diabetes in the United States and Europe. While Asians generally have a much lower incidence of type 1 diabetes, Japan is also experiencing a rise in cases. Such changes are most likely linked to some environmental or behavioral factor. Possibilities include climate, exposure to some virus, and infant diet.
Temporal clusters of type 1 diabetes cases (those that occur around the same time-whether within families, a school, or a geographical region) have also prompted people to suspect an environmental agent. However, given that the development of diabetes takes many years in most cases, as the body's immune system malfunctions and begins destroying the body's insulin-producing cells, a clustering in time seems more likely due to chance than a common cause.
If an immediate relative (parent, sibling, or child) has type 1 diabetes, one's risk of developing the disease is 10 to 20 times that of the general population. Your risk can rise from 1 in 100 to roughly 1 in 10 or possibly higher, depending on which family member has diabetes and when he or she developed it:
- If one child in a family has type 1 diabetes, siblings have about a 1 in 10 risk of developing it by age 50.
- The risk for a child of a parent with type 1 diabetes is lower if it is the mother who has diabetes than if it is the father. If the mother is 25 or younger when the child is born, the child's risk is 1 in 25, compared with about 1 in 17 when the father has diabetes. When the mother is over age 25, the risk drops to 1 in 100 - virtually the same as for the average American. The risks are somewhat higher when a parent developed diabetes before age 11.
- About 1 in 7 people with type 1 diabetes has a condition known as type 2 polyglandular autoimmune syndrome. These people have thyroid disease, malfunctioning adrenal glands, and sometimes other immune disorders. When a parent has this syndrome, the child's risk of developing it-including type 1 diabetes-is 1 in 2, according to the American Diabetes Association.
Caucasians have a higher risk of type 1 diabetes than any other race. Whether this is due to differences in environment or genes is unclear. Even among whites, most people who are susceptible do not develop diabetes, so scientists are studying what environmental factors may be at work. Genes influencing the function of the immune system are the most closely linked to susceptibility, regardless of race. One of those genes is HLA-DR. Most Caucasians with diabetes carry gene variants (alleles) 3 or 4 (or both) of the HLA-DR gene, known as HLA-DR3 or HLA-DR4. The HLA-DR7 allele plays a role in diabetes in blacks, while HLA-DR9 allele is significant in diabetes among Japanese.
Some experts believe that a trauma such as a car crash or a viral infection like mumps can trigger the onset of Type 1 diabetes. Such events increase the body's insulin requirement and strain the insulin production machinery if it is being destroyed by a malfunctioning immune system. As the demands on the body increase, they are thought to tip the body into diabetes without actually being a "cause" of the disease.
It is also theorized that a link exists between coxsackie virus, which causes meningitis, and type 1 diabetes, though the connection is unclear. Scientists do have some significant evidence that mumps does not trigger diabetes, however. A Maryland study showed that despite a great decline in mumps cases after the mumps vaccine was introduced 30 years ago, the incidence of type 1 diabetes did not change.
Some scientists believe early diet may play a role, since children who have developed type 1 diabetes are less apt to have been breastfed for a prolonged period. While some studies have pointed to exposure to cow's milk as a factor, much remains to be learned about its importance. To be prudent, mothers of infants at heightened risk of developing diabetes may want to breastfeed as long as possible and use cow's milk in moderation after the baby is weaned.
Last reviewed on 11/10/2008
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