Harvard Men's Health Watch

Preventing diabetes: Understanding and diagnosing the disease

In the era of SARS, bird flu, and"ŠHIV/AIDS, many Americans are concerned about epidemics. It's a reasonable concern, but it often overlooks a major epidemic that is already gripping our nation: diabetes. Unlike epidemics that begin with biologic agents in other parts of the world, diabetes is a home-grown threat. Like other epidemics, though, simple measures can prevent the disease from spreading "" but only if we understand diabetes and heed the call to action.

The epidemic

About 21 million Americans have diabetes, but a third of them don't know it. That means 7% of American adults are diabetic and many more have impaired fasting glucose, which is better known as pre-diabetes. These are worrisome figures, but the explosive increase in the disease is more worrisome still. The prevalence of diabetes increased by about 40% during the 1990s and rose by another 8% in the year 2000. And every projection indicates that it will continue to grow in the future.

Since the disease becomes more common as people age, it's tempting to ascribe the surge in diabetes to our aging population. That's part of the explanation "" but only a small part. In fact, the greatest increase in diabetes has occurred in children and adolescents.

Does it matter?

It sure does. Men with diabetes are about twice as likely to develop heart disease as those without diabetes. In addition, diabetes is a major cause of kidney failure, loss of vision, peripheral artery disease, leg amputation, and cognitive impairment. And if that's not bad enough, remember that men with diabetes are much more likely to develop erectile dysfunction than healthy men, and the problem starts 10 to 15 years earlier in diabetics. Diabetics also have a higher risk of benign prostatic hyperplasia (BPH).

All in all, diabetes shortens life expectancy by about 13 years; no wonder it's the sixth leading cause of death in the United States, taking about 300,000 lives annually. And diabetes is expensive. It drains the U.S. economy of over $130 billion a year and consumes about one in four Medicare dollars.

What is diabetes?

To understand diabetes, you should first understand how your body handles glucose, the sugar that fuels your metabolism. After you eat, your digestive tract breaks down carbohydrates into simple sugars that are small enough to be absorbed into your bloodstream. Glucose is far and away the most important of these sugars, and it's an indispensable source of energy for your body's cells. But to provide that energy, it must travel from your blood into your cells.

Insulin is the hormone that unlocks the door to your cells. When your blood glucose levels rise after a meal, the beta cells of your pancreas spring into action, pouring insulin into your blood. If you produce enough insulin and your cells respond normally, your blood sugar level drops as glucose enters the cells, where it is burned for energy or stored in your liver as glycogen for future use. Insulin also helps your body turn amino acids into proteins and fatty acids into body fat. The net effect is to allow your body to turn food into energy and to store excess energy to keep your engine running if fuel becomes scarce.

A mild elevation of blood sugar doesn't produce any symptoms, which is why diabetes often goes undiagnosed for four to six years, if not longer. But even mild diabetes is dangerous, since it damages blood vessels and other vital organs. When sugar levels get higher, they produce symptoms that may include fatigue and blurred vision. Excess sugar spills into the urine, taking water with it. This produces excessive urination and dehydration, which lead to increased thirst. Excess hunger is another symptom, and weight loss may develop despite a hearty appetite. This happens because while the blood has too much sugar, the cells don't get enough. Diabetes is starvation in the midst of plenty.

Over time, some men develop symptoms of diabetes-related heart disease, kidney disease, eye disease, or blood vessel disease. That's why every man with any of these problems, or with erectile dysfunction, should be tested for diabetes. And since prompt and aggressive treatment can head off many complications of the disease, every healthy man should also be tested regularly starting at age 45.

The three types of diabetes

The name diabetes encompasses three different disorders that are all marked by abnormally high blood sugar levels. All forms of diabetes develop when the pancreas is unable to supply enough insulin to meet the body's demands. In some cases, the problem is a low supply; in others, the tissues don't respond to insulin as they should; and in still others, it's both.

Type 1 diabetes was formerly known as juvenile or insulin-dependent diabetes. It usually begins abruptly before the age of 20, often with a critical rise in blood sugar levels. The disease is caused by a combination of genetic abnormalities and environmental triggers that cause the body's immune system to attack the pancreas, destroying its ability to produce insulin. Since insulin is required for glucose to enter cells, blood sugar levels rise sharply. Type 1 diabetes is the most severe form of the disease, but it accounts for only about 5% of cases in the United States. Lifelong insulin therapy is mandatory.

Type 2 diabetes was once called adult-onset or non-insulin-dependent diabetes. In most cases, the main problem is insulin resistance. The pancreas produces reasonable amounts of the hormone, but the body's tissues don't respond properly, so blood sugar levels are abnormally high. Oral medications can help many patients compensate for insulin resistance. But over time, the ability of the overtaxed pancreas to secrete insulin may run down, requiring insulin therapy.

More than 90% of diabetics have type 2 disease. Genes play a role in risk. America's gene pool has not changed substantially since the mid-1970s while the prevalence of type 2 diabetes has soared. That's because lifestyle factors are the major contributors to the disease, with obesity heading the list.

Type 2 diabetes depends less on who your parents are than on how you live. And that means you can protect yourself from this major chronic illness with a series of simple lifestyle choices.

Gestational diabetes, which occurs during pregnancy, increases the risk of complications for mother and child. Blood sugar levels return to normal after delivery, but many women develop type 2 diabetes later in life.


The American Diabetes Association (ADA) has proposed a simple standard for the diagnosis of diabetes: a fasting blood sugar of 126 mg/dL or higher, providing the result is confirmed on a second test. To be accurate, the blood should be obtained after 8 hours without any caloric consumption. Fasting blood sugars between 100 and 125 indicate impaired glucose tolerance, a milder condition that may lead to diabetes; levels below 100 are officially normal. Still, an important 2005 study of 74,309 healthy young men found that fasting glucose levels between 87 and 99 indicate an increased risk for future diabetes. It's a warning for all of us.

Although a fasting blood sugar of 126 is the standard for diagnosing diabetes, two other criteria are also available. Any blood sugar level above 200 suggests the diagnosis, even if it's obtained after eating; to be officially diagnosed as diabetic, however, people with random sugars of 200 or higher should also have symptoms of the disease, such as increased thirst and urination or unexplained weight loss.

A third way to evaluate diabetes is to see what percent of the oxygen-carrying hemoglobulin molecules in a person's red blood cells have glucose attached to them. A single glycosylated hemoglobin (HbA1C) level reflects a person's average blood sugar during the preceding 30 days. Normally, it's about 5.0, meaning that 5% of the hemoglobulin molecules have glucose attached to them. A level above 7.0 almost always indicates diabetes.

When should you be tested for diabetes? It's most convenient when you're having a regular checkup, especially if you are already fasting for a cholesterol check. But that doesn't necessarily mean a test every year. The ADA recommends a test every three years for people 45 or older. Individuals with risk factors such as being obese or overweight, having a diabetic parent or sibling, or having high blood pressure or high cholesterol levels should begin testing earlier and should have repeat tests as often as once a year. Needless to say, men who have had borderline or high blood sugar readings in the past should also be tested regularly.

Diagnosing diabetes early is important because prompt and aggressive treatment can help ward off the often-deadly complications of the disease. But preventing it from developing in the first place is even better. It sounds too good to be true, but it can be done.