JAMA notes that just 11% of more than 2,700 recommendations approved by cardiologists for treating heart patients are supported by high-level scientific evidence. And the BMJ weighs in with the sobering statistic that a mere 13% of medical treatments are known to be beneficial, while 48% are of unknown effectiveness.

A new book, Dance With Chance, cites these statistics and sheds some light on the phenomenon. It starts with the premise that medicine is not an exact science. The authors then go on to debunk certain conventional wisdoms about health care such as what they call the ‘cholesterol myth.’

Some cholesterol-lowering drugs are not only ineffective, they say, but may even increase the risk of heart attacks while also producing serious, negative side effects. They also cite the fact that in southwest France, famous for producing the high-cholesterol delicacy foie gras and where the denizens consume copious amounts of butter and other fatty products, deaths from cardiovascular disease are 39.8 per 100,000 as opposed to 196.5 per 100,000 in the US. And salt? JAMA has apparently suggested that ‘restricting dietary sodium intake’ has only a minimal effect on blood pressure. Empirical evidence, they say, reveals no difference in life expectancy between those who undergo annual medical check-ups than those who don’t.

So does the book offer any prescriptions? The authors claim: “pressures from doctors, the media, the pharmaceutical industry, and society in general are sufficient to explain why the apparent certainty of medical science is just another illusion.”

As for the inexactitude of medicine, one need look no further than the PSA screening for prostate cancer, which produces a substantial number of false positives, meaning that many men with high levels have no cancer but might undergo unnecessary prostatectomy or other invasive procedures.

So, how do patients perceive risk? For example, do they really discern whether, upon the discovery of prostate cancer, the options for surgery or for radiation therapy are preferred? In that example, the patient’s choice of treatment can be strongly influenced by whether the risks are presented in terms of survival data or mortality data. Another good example is the uproar over the change in recommendations over Pap smears and breast cancer screening by US health authorities. How does a patient understand the difference between a one-in-400 versus a one-in-2800 risk of getting cancer, not to mention the added risk of radiation exposure?

In an extensive review of this issue in the journal Quality and Safety in Health Care, AJ Lloyd notes that people’s decision-making is not strictly rational but rather is subject to systematic biases. People employ simplifying heuristics in judgment and decision-making, says Lloyd, by coding risks qualitatively as simply ‘dangerous’ or ‘safe’ rather than retaining quantitative information (eg, 15% or 8.9 per 1000). Patients also commonly view hazards as more risky for other people than for themselves. He concludes that many patients have poor comprehension and recall of risk information.

The irrationality of interpreting risk was well illustrated in the aftermath of the September 11, 2001 terrorist attacks. While the deaths from those attacks were estimated to be 3000, there was an add-on death rate of 5,000 Americans resulting from a widespread move away from air travel (in which overall fatalities are minimal) to road travel (in which fatalities are thousands of times higher).

The Dance With Chance authors might be a bit cavalier in advising, “If you feel good, there’s no need to take a test to see if you’ve got an illness.” Nonetheless, they join forces with Jerome Groopman, author of How Doctors Think in suggesting a partnership between patient and doctor. In such an arrangement, patients might ask their physicians about the benefits and dangers of a given procedure, what the alternatives might be, what the side effects are of any associated drugs, and what the outcome is likely to be from doing nothing – and finally what’s it likely to cost and will the insurance cover it.

As Alexis Skoufalos, EdD, associate dean for continuing education at Thomas Jefferson University’s School of Population Health, puts it: “Comparative effectiveness is at the heart of that comment. A lot has to do with making sure that the patient is actively involved in decision-making. Communication with patients, their family members, and caregivers regarding the options, etc, is important.”

But AJ Lloyd notes: “In the present context, risk is considered to be the product of the probability of an outcome and the severity of that outcome. Clearly understanding both aspects of risks are crucial when patients are asked to make decisions about their treatment.” In other words, it’s not enough to understand the risk of a heart attack; a patient also needs to realize what a heart attack is and how it will affect his life, in the short- and long-term.

Lloyd AJ. I. Communicating and understanding risk: The extent of patients’ understanding of the risk of treatments. Qual Health Care 2001;10:i14-i18. doi:10.1136/qhc.0100014.

Makridakis S, Hogarth R, Gaba. Dance With Chance. Oneworld Publications; 2009.

David Woods, PhD is CEO of BioScriptUS and former editor of Health Outcomes Communicator.