At your last medical exam you may have been tested for type 2 diabetes as part of a basic blood panel. If you were not, should you have had your blood sugar (glucose) measured? It depends on your age, weight, blood pressure and/or other risk factors for diabetes. But, in fact, there’s a surprising amount of disagreement about screening for diabetes. Recent research and position papers have lent support to both sides of the debate.
Type 2 diabetes, previously called noninsulin dependent or adult-onset diabetes, accounts for 90 to 95 percent of cases of diabetes. Diabetes is a breakdown in the body’s ability to utilize blood sugar efficiently. Before screening became widely used, the disease was diagnosed when people developed symptoms, such as unusual thirst or frequent urination.
It’s estimated that 26 million Americans have diabetes, of whom 7 million have not been diagnosed. And those who have been diagnosed typically have had the disease many years before it was diagnosed.
Another 80 million have prediabetes. That means their blood sugar is elevated (100 to 125 mg/dL after fasting) but not high enough to be categorized as diabetes. Many of them will eventually develop full-blown diabetes.
The incidence of diabetes and prediabetes has been rising rapidly, largely because of the obesity epidemic.
Early detection of diabetes can identify cases before symptoms and complications develop. That way, people can take steps (such as losing weight, improving their diet or taking medication) to minimize the damage to organs and blood vessels caused by years of high blood sugar levels—and, it’s hoped, avoid later complications of diabetes, such as heart disease, stroke and diseases of the eyes, nerves and kidneys. Screening is usually done by simple blood tests.
Routine screening: yes
The American Diabetes Association (ADA) is the leading proponent of screening. It recommends that health care providers “consider” screening asymptomatic people starting at age 45. Overweight or obese adults should be tested earlier if they have any of the following additional risk factors: a parent or sibling with diabetes; physical inactivity; belonging to a high risk racial/ethnic group (such as blacks, Hispanics, Asians and Native Americans); high blood pressure, low HDL (“good”) cholesterol, or high blood triglycerides; a history of cardiovascular disease or of gestational diabetes during pregnancy. If results are normal, testing should be repeated at least every three years, the ADA advises.
Routine screening: maybe
In 2008, the U.S. Preventive Services Task Force, which evaluates evidence on medical matters, limited its recommendation for diabetes screening to people with higher blood pressure (defined here as sustained levels of 135/80 or higher). That’s because the combination of the two disorders greatly increases cardiovascular risk, and thus someone with both should reduce blood pressure even lower than the standard target numbers. For all other asymptomatic people, the Task Force concluded, there’s insufficient evidence to assess the value of routine testing. The decision to screen or not should be made on an individual basis.
Last year the Canadian Task Force on Preventive Health Care also narrowed its guidelines to say that only people at fairly high risk for diabetes (based on a validated risk calculator) should be screened.
However, also in 2012, a coalition of 18 major health organizations issued a paper calling for the U.S. Task Force to broaden its recommendations for diabetes screening to cover people with other risk factors, especially those who are overweight or obese.
Routine screening: no?
What could be wrong with diabetes screening? Unlike some cancer screening tests, such as PSA for prostate cancer, diabetes screening causes no major harms. But it has been hard to prove that it prolongs lives. This was seen in an English study published in The Lancet late last year, the first major randomized trial on diabetes screening. It found that among 15,000 people (ages 40 to 69) at high risk for diabetes, those who were screened and, when necessary, treated over a 10-year period, did not live longer than those who were not screened. While this study had some weaknesses—for instance, the subjects were overwhelmingly white and mortality rate was the only focus (not quality of life)—it was not the first that failed to find a benefit.
Though there’s no proof yet that early detection of type 2 diabetes by routine screening reduces the risk of long-term complications, we think it likely does. So you should start getting tested for diabetes in middle age—the ADA’s suggestion of 45 is a reasonable age to begin, unless you have risk factors, which would call for earlier screening. If your health care provider hasn’t tested you already, talk to him/her about it, especially if are overweight or have hypertension or a family history of diabetes.
If you are diagnosed with diabetes, you’ll be advised to lose weight if you’re overweight, exercise more, improve your diet, quit smoking if you smoke and start drug therapy if necessary. If you have prediabetes, these same diet and lifestyle changes can help you avoid diabetes.
The goal of early detection is not merely to get people started on diabetes medication earlier, but to help them avoid having to take medication, if possible, or at least postpone or minimize its use. At the same time, a diagnosis of diabetes means it’s even more important for you to also control your blood pressure and cholesterol levels adequately. If screening for diabetes serves as an additional incentive for people to lose weight and start exercising, that can only be beneficial.
By the way, the Affordable Care Act ensures that, in new health insurance plans, people at higher risk for developing diabetes can receive diabetes screening and diet counseling with no out-of-pocket costs.