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My first car was a ’65 Ford Fairlane wagon. It was a fairly simple—albeit large—vehicle. I could even do some of the work on it myself. There was a lot of room under the hood and few electronics. The only engine sensors were a temperature gauge and an oil-pressure gauge.

Things are very different with my ’99 Volvo. There’s no extra room under the hood—and there are lots of electronics. And then there are all those little warning lights sensing so many different aspects of my car’s function that they have to be connected to an internal computer to determine what’s wrong.
Cars have undoubtedly improved over my lifetime. They are safer, more comfortable, and more reliable. The engineering is better. But I’m not sure these improvements have much to do with all those little warning lights.
Check-engine lights—red flags that indicate something may be wrong with the vehicle—are getting pretty sophisticated. These sensors can identify abnormalities long before the vehicle’s performance is affected. They are making early diagnoses.

Maybe your check-engine lights have been very useful. Maybe one of them led you to do something important (like add oil) that prevented a much bigger problem later on.

Or maybe you have had the opposite experience.

Check-engine lights can also create problems. Sometimes they are false alarms (whenever I drive over a big bump, one goes off warning me that something’s wrong with my coolant system). Often the lights are in response to a real abnormality, but not one that is especially important (my favorite is the sensor that lights up when it recognizes that another sensor is not sensing).
Recently, my mechanic confided to me that many of the lights should probably be ignored.

Maybe you have decided to ignore these sensors yourself. Or maybe you’ve taken your car in for service and the mechanic has simply reset them and told you to wait and see if they come on again.

Or maybe you have had the unfortunate experience of paying for an unnecessary repair, or a series of unnecessary repairs. And maybe you have been one of the unfortunate few whose cars were worse off for the efforts.

If so, you already have some feel for the problem of overdiagnosis.

I don’t know what the net effect of all these lights has been. Maybe they have done more good than harm. Maybe they have done more harm than good. But I do know there’s little doubt about their effect on the automotive repair business: they have led to a lot of extra visits to the shop.

And I know that if we doctors look at you hard enough, chances are we’ll find out that one of your check-engine lights is on.

A routine checkup

I probably have a few check-engine lights on myself. I’m a male in my midfifties.
I have not seen a doctor for a routine checkup since I was a child. I’m not bragging, and I’m not suggesting that this is a path others should follow.
But because I have been blessed with excellent health, it’s kind of hard to argue that I have missed out on some indispensable service.

Of course, as a doctor, I see doctors every day. Many of them are my friends (or at least they were before they learned about this book). And I can imagine some of the diagnoses I could accumulate if I were a patient in any of their clinics (or in my own, for that matter):

• From time to time my blood pressure runs a little high. This is particularly true when I measure it at work (where blood pressure machines are readily available).
Diagnosis: borderline hypertension

• I’m six foot four and weigh 205 pounds; my body mass index (BMI) is 25.
(A “normal” BMI ranges from 20 to 24.9.)
Diagnosis: overweight

• Occasionally, I’ll get an intense burning sensation in my midchest after eating or drinking. (Apple juice and apple cider are particularly problematic for me.)
Diagnosis: gastroesophageal reflux disease

• I often wake up once a night and need to go to the bathroom.
Diagnosis: benign prostatic hyperplasia

• I wake up in the morning with stiff joints and it takes me a while to loosen up.
Diagnosis: degenerative joint disease

• My hands get cold. Really cold. It’s a big problem when I’m skiing or snowshoeing, but it also happens in the office (just ask my patients). Coffee makes it worse; alcohol makes it better.
Diagnosis: Raynaud’s disease

• I have to make lists to remember things I need to do. I often forget people’s names—particularly my students’. I have to write down all my
PINs and passwords (if anyone needs them, they are on my computer).
Diagnosis: early cognitive impairment

• In my house, mugs belong on one shelf, glasses on another. My wife doesn’t understand this, so I have to repair the situation whenever she unloads the dishwasher. (My daughter doesn’t empty the dishwasher, but that’s a different topic.) I have separate containers for my work socks,
running socks, and winter socks, all of which must be paired before they are put away. (There are considerably more examples like this that you don’t want to know about.)
Diagnosis: obsessive-compulsive disorder

Okay. I admit I’ve taken a little literary license here. I don’t think anyone would have given me the psychiatric diagnoses (at least, not anyone outside of my immediate family). But the first few diagnoses are possible to make based solely on a careful interview and some simple measurements (for example,
height, weight, and blood pressure).