(I'm giving you fair warning: this is a long piece, but I've divided it up for you. Each part will do fine on its own, but of course I'd like you to read both. You'll be a better person for it. --PalMD)
Part I: Uncommon Sense
Everything was OK until Christmas; before that she felt fine. Then she began to feel tired. She was having trouble sleeping so, she thought, maybe that was it. She tried some sleeping pills from the drugstore, but she still didn't feel right. Just doing a load of laundry wore her out. She and her husband normally got together with the same set of friends every New Year's Eve, but this year she was too tired. She hated New Year's Day, because every year she made another set of resolutions, usually about her weight. When she got on the scale this year, she was up twenty pounds. Twenty pounds! Impossible! Her pants fit more or less the same, although her shoes were tight. In fact, she'd been wearing unlaced shoes around the house and couldn't really fit into most of her socks. She went to bed disappointed.
That night she woke out of a sound sleep and sat bolt upright---she couldn't breathe. She ran to the window, threw it open, and gulped in cold air, slowly feeling better. Her husband called an ambulance.
Heart failure is a condition in which the heart isn't pumping well enough to meet the body's needs. Fluid can back up into the lungs, making it hard to breathe, the legs can become swollen; and depending on the severity, heart failure can lead to sudden death. One of the mainstays for the treatment of heart failure is a class of medications called diruetics which cause patients to urinate more, decreasing swelling and easing breathing. But diuretics don't really affect the heart itself, they just drain off fluid, alleviating some symptoms. It seems logical that if a failing pump is responsible for many of the symptoms of heart failure (and it is), then medications that improve the pumping action would be a good thing, and those that decrease it bad. It's common sense. It's intuitive.
Medical students and residents often dread discussions about statistics (a characteristic which I'm sure is not unique to these groups). And who can blame them, really? Statistical analysis is inherently non-intuitive. Its purpose is to separate us from our own natural inclinations to identify patterns (our "intuition") in order to systematically study relationships between variables of interest.
A number of years ago, doctors noted that a certain class of drugs ("inotropes") improved the pumping action of the heart. Patients with heart failure were given these drugs, and their heart function improved. Common sense, right? But when the topic was studied systematically, researchers found that these drugs actually increased mortality. Oops (in this case, "oops" means people dying).
Another group of drugs called beta-blockers can reduce the pumping action of the heart, and for years were assiduously avoided in heart failure---until study after study showed that beta-blockers actually decrease mortality in chronic heart failure.
Common sense can give us a starting point, but until the big questions are examined systematically, we are in danger of intuiting our patients to death. Beta blockers are now a mainstay of heart failure treatment, and inotropes a rarely-used footnote, a treatment reserved for a specific set of circumstances. But we didn't figure that out through common sense alone.
Part II: Does smoking pot cause cancer? Continue Reading »