Epidemics by definition

Epidemics can sometimes be created. One of the most common tactics is to change the definition. When diagnostic criteria is broadened, suddenly, with the stroke of a pen, new cases can appear to explode in number.

The World Heart Federation, American College of Cardiology, American Heart Association and the European Society of Cardiology have been championing new criteria for heart attacks over recent years, and will officially release it next month in the Journal of the American College of Cardiology and in the AHA journal, Circulation. The new definition will use elevations of troponin levels, rather than the traditional cardiac biomarkers, such as the MB-CK enzyme, along with traditional symptoms. Troponin is more sensitive and is released more quickly with even the slightest heart cell damage or ischemia, meaning it will diagnose more heart attacks, even including other things that can cause temporary elevations in troponin levels. Troponin levels can rise for many reasons beyond heart attacks, such as acute or chronic myocarditis (heart inflammation), congestive heart failure, infections, kidney disease, dermatomyositis, polymyositis (muscle inflammation), pulmonary embolisms, as well as after therapeutic procedures like coronary angioplasty, electrophysiological ablations, other heart catheterization procedures, or electrical cardioversions.

What will this new definition mean? Dr. Richard N. Fogoros, M.D., described it on his blog this past week, writing:

1) Under the new definition, many patients with chest pain who previously would be told a heart attack had been “ruled out" will now be diagnosed as actually having a heart attack. Accordingly, because they indeed do have unstable coronary artery disease, they will get more appropriate and more aggressive therapy than they would have received in the past....

2) The number of patients who are diagnosed with heart attack will increase by at least 25% under this new definition, according to some estimates. Officially, the incidence of heart attacks will rise. Therefore, in a year or two expect breathless news stories about the alarming new “epidemic" of heart attacks. Any time we get better at making earlier diagnoses of any disease -— whether coronary artery disease, infectious disease, or cancer — the reported incidence of that disease will go up. This is something we need to remember whenever experts call for new federal regulations (which seems to be the main job of experts), based on the increasing incidence of some disease or other.

3) Because these “new" heart attack patients will have a milder form of heart attack, the acute mortality rate reported for heart attacks will go down. It will be very tempting for some to use this entirely predictable improvement in acute outcomes to justify the expensive technologies or procedures that will be said to have produced it. Careful analysis will actually be required to tease out the reasons for improvements in clinical outcomes. We already know of one — a new definition of heart attack.

And when claims of skyrocketing heart attacks make the news — perhaps attributing it to ‘obesity,’ the evils of our modern diets or lifestyles, pollution or whatever — how many will be told that the definition criteria had simply changed? Or, will it be like so many other popularized ‘epidemics’ and people just readily accept them and not take a critical look at the definitions?

“Overweight:”Definition changed from BMI ≥ 27 to BMI ≥ 25 by the U.S. National Heart Lung and Blood Institute in 1998, instantly increasing by 43% the numbers of Americans, an additional 30.5 million, deemed ‘overweight.’

“High cholesterol:”Definition changed from a total cholesterol ≥ 240 to ≥ 200 in 1998 increasing by 86% the numbers of Americans labeled has having high cholesterol, an additional 42.6 million adults.

“Hypertension:”Definition changed in 1997 from 160/100 to 140/90, instantly adding 35% more Americans, 13.5 million, to the rosters of hypertensive. A new definition for ‘prehypertension’ in 2003 increased to 58% the Americans believing they have hypertension.

“Diabetes:” Definition changed from a fasting glucose of ≥ 140 to ≥ 126 in 1997 by the American Diabetes Association and WHO Expert Committee on the Diagnosis and Classification of Diabetes Mellitus, increasing by 14% and 1.7 million the people diagnosed with diabetes. With the proposal of a new term, ‘prediabetes’ by the First International Congress on Prediabetes, and promoted by the International Diabetes Federation (sponsored by 12 pharmaceutical companies), 40% of the adult population was added to the rosters believing they have diabetes and are in need of treatment.

© 2007 Sandy Szwarc. All rights reserved.