Wholesale returns of conjecture
Newspapers and websites around the country are reporting a story coming out of the American Heart Association's Cardiovascular Disease Epidemiology and Prevention annual conference in Palm Harbor, Florida yesterday. Medical researcher Dr. Kirsten Bibbins-Domingo, an assistant professor of medicine and epidemiology at the University of California, San Francisco, reported that if Americans cut just one gram of salt from their daily diet, there would be 250,000 fewer new cases of heart disease and more than 200,000 fewer deaths over a decade.
This dramatic statement was not the result of any clinical trials or observed data but rather the product of a computer simulation called the Coronary Heart Disease Policy Model. Many such statistical models are available and were the subject of a systematic review in 2006. The conclusion of this review stated that
"…few Coronary Heart Disease Policy Models have been calibrated, replicated or validated against minimum quality criteria. Before being accepted as a policy aid, any model should explicitly include a statement of its aims, assumptions, outputs, strengths and limitations."
Despite this, most media devoted to food and health report this study without any qualifications - as if it were fact and not the consequence of speculation and assumption. It's little wonder that in his book "Life on the Mississippi" Mark Twain wrote:
"There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact."
Over the last number of years we have heard, seen and read about hundreds, of medical breakthroughs and pending calamities that vanished into thin air after a short period, never to be heard from again. Most of these were based on conjectures and assumptions that never panned out, yet, the media, consumer advocates and the medical establishment latched onto them without any reference to the quality of data - as if they were proven fact.
It's a pity that there isn’t a requirement to have all public statements regarding health, conform to a minimum level of evidentiary quality. At the very least, there should be a system established so that consumers will be informed of the level of evidence behind any health-related public statements or claims. After all, the consumer advocacy movement, followed by the medical establishment, was the first to insist on food labels so that consumers would be better informed as to what they were getting for their money. Why shouldn’t the same sentiment govern the public statements consumers get concerning our health, so that they can judge their value and trustworthiness?
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