Each producer tries to convince the public that something is dangerously wrong, or about to go wrong, and that immediate steps must be taken to remedy the situation. An indifferent public is first galvanized into becoming a market of alarmed consumers by constant reminders of myriad threats to health, and then convinced of the need for more and more products and services to protect them. In the process, deep-seated fears about disease are mobilized, and insecurities about health and longevity are intensified. As a result, many come to feel less secure about their health, more worried about the possibility of disease, more absorbed in trivial symptoms.
Fast forward to this year, when a blog post from the U.S. Department of Health and Human Services advised, "It's never too early to prevent type 2 diabetes." Noting that women with high blood sugar levels in pregnancy (gestational diabetes) are more likely to develop type 2 diabetes later in life, this post suggested that mothers be tested for diabetes 6 to 12 weeks after the birth, then tested again periodically, with more frequent testing if their results showed prediabetes.
When medical and public health professionals talk about diabetes prevention, they are generally referring to helping people with prediabetes (high blood sugar levels that aren't high enough to meet diagnostic criteria for diabetes) improve their diets, become more physically active, and (if overweight) lose extra weight. In March, the Centers for Disease Control and Prevention and the American Medical Association announced the Prevent Diabetes: STAT campaign, with STAT standing for Screen, Test, Act-Today. Since few persons with prediabetes have recognizable symptoms, the reasoning goes, physicians need to find them by screening. But what is the evidence that screening for prediabetes makes a difference in long-term health outcomes?
Let's start with screening for diabetes. In 2008, the U.S. Preventive Services Task Force recommended that adults with blood pressures over 135/80 be screened for diabetes, not from direct evidence that screening was beneficial, but because at that time blood pressure goals were lower for diabetic patients. However, the 2014 JNC-8 hypertension guideline set the same goal blood pressure of 140/90 for adults younger than 60 years regardless of diabetes status, removing this rationale for screening.
So when the USPSTF updated their 2008 recommendations, they would need to find proof that earlier treatment of screen-detected diabetes (as opposed to clinically detected) prevented or delayed patients from going blind, losing limbs, requiring dialysis, having heart attacks, or dying as a result of their disease. The Task Force completed its review last November. The review found no evidence that screening for diabetes, even in high-risk persons, prevented or delayed any of the those outcomes. In fact, two randomized trials of screening for diabetes found no differences in mortality rates after 10 years of follow-up. These findings would typically have resulted in a "I" (insufficient evidence) statement or "D" (don't do) recommendation. Instead, the USPSTF provisionally recommended screening a much larger group of adults than before, reasoning that in the process of screening for diabetes, physicians would find lots of people with prediabetes and hopefully be able to prevent them from developing diabetes.
Huh?
Both the USPSTF review and a more recent review commissioned by the Community Preventive Services Task Force clearly showed that combined diet and physical activity promotion programs can slow (or sometimes stop) the progression from prediabetes to diabetes. No argument there. What we don't know is if finding more adults with prediabetes (and, since so many are thought to be undiagnosed, creating an epidemic of prediabetes) will help them live longer or better. Most persons with prediabetes are overweight, sedentary, and/or consume an unhealthy diet. Family physicians already provide lifestyle counseling to these patients. And if (like a few of my own patients with prediabetes) they happen to be normal-weight long-distance runners who haven't touched junk food in years, I just tell them to keep doing what they're doing.
Two editorials that accompanied publication of the USPSTF and Community Task Force reviews in Annals of Internal Medicine essentially argued that we don't need any more evidence to go out and screen everybody for prediabetes. Drs. K.M. Venkat Narayan and Mary Beth Weber wrote, "Much of the debate around screening for prediabetes and diabetes focuses on the lack of direct evidence from randomized, controlled trials comparing screened with unscreened persons on a hard outcome, such as CVD or mortality. However, such a definitive trial of hyperglycemia screening is infeasible, unrealistic, and arguably unethical ..."
Tell that to the authors of exactly this type of randomized trial which has been going on for more than a decade! Similarly, Dr. Ronald Ackermann argued, "As a society, we should no longer hold for ransom the potential to reduce the burden of diabetes by continuing to await further evidence that interventions will be cost-saving or prevent myocardial infarctions or deaths."
Well, while we're talking about hostage-taking, consider that being told that he or she has diabetes or prediabetes makes a patient immediately feel worse (or as Dr. Barsky would have put it, feel less secure about their health, more worried about the possibility of disease, [and] more absorbed in trivial symptoms). In my view, widespread screening for prediabetes will only become ethically justifiable when we have proof that it will lead to people living longer or better.