Your Medical Mind_ How to Decide What Is Right for You - Jerome Groopman [23]
The search for the “best choice” takes us to an eighteenth-century Dutch mathematician named Daniel Bernoulli. At the time, Holland was a hub of world commerce, and its traders were making decisions about buying and selling everything from Asian spices to Caribbean sugarcane. Bernoulli was born in the city of Groningen in 1700. His father, a mathematician, encouraged him to study business to assure himself a good income. At first, Bernoulli refused. Later, he agreed to study both business and medicine, but only under the condition that his father instruct him privately in mathematics. He ultimately became a professor of medicine, metaphysics, and natural philosophy at the University of Basel in Switzerland. His seminal work in fluid mechanics helps explain how birds fly and was crucial to the development of airplanes. In 1738, he turned his attention to probability theory and devised a formula that he believed would calculate the wisdom of any decision where the outcome was uncertain and the choice involved risk. He proposed that by multiplying the probability or chance of an outcome by the utility of that outcome, meaning how much we value it, we obtain a number, the “expected utility.” The highest number, the greatest “expected utility,” indicates the most rational choice.
[(probability of outcome) × (utility of outcome) = expected utility]
Bernoulli was thinking mostly about choices that involved goods and money, and his formula for “rational” decision making has been widely applied in economics. Over the last few decades, however, “expected utility” theory has moved beyond economics and into clinical medicine. Researchers have proposed that doctors should advise a patient like Patrick Baptiste of his best option by using Bernoulli’s calculations. First, the physician would tell Patrick the probability of a clinical outcome and then ask him to place a numerical value or “utility” on his health state if that outcome occurred. Multiplying the chance that a particular outcome might occur by the numerical value Patrick placed on living with that outcome yields a number; the highest number indicates his most rational or “best” choice.
This formula has great appeal, as it pinpoints two key components we all should consider when choosing among different options: what is likely to happen and how our life would be affected if it did happen. All of us want to live the longest life with the highest quality. In the case of Graves’ disease, all three options—radioiodine, surgery, medication—can yield the desired positive outcome, control of hyperthyroidism. But there are differences in potential negative outcomes and side effects, as well as in quality of life in the future.
Let’s first imagine that the endocrinologist advising Patrick used Bernoulli’s equation. As all the treatments can be effective in controlling hyperthyroidism, the probability of this outcome is equivalent for all three therapies. What differs are the potential side effects. Patrick’s physician views the side effects of antithyroid medication and surgery as much more serious than those of radioactive iodine. So he would assign these treatments a lower “utility” or value, and he would logically arrive at treatment with radioactive iodine as the best option. He framed his discussion with Patrick in these terms.
But Patrick would solve the same equation quite differently. He cringed when the endocrinologist said that it was “no big deal” to destroy his thyroid gland with radioactive iodine so that he would have to take a thyroid hormone pill every day for the rest of his life. “I don’t like having to take medication every day for my diabetes. And I didn’t want to commit myself to taking another pill every day—to have another chronic condition.” He explained that “when I watched my diet, exercised, and controlled my weight, I was able to come off insulin injections.