John B. Hickam, 1914-1970 (Photo/Smithsonian Institution Archives)
John B. Hickam, 1914-1970 (Photo/Smithsonian Institution Archives)

Medical decisions can come down to Occam’s razor vs. Hickam’s dictum

A 64-year-old woman who I will call Doris came to see me because she’d been feeling fatigued for more than six months. She had not seen a doctor for many years. Doris told me she slept well, at least seven hours per night, and had no other medical problems she was aware of.

As part of my initial evaluation, I had her complete a standard mental-health questionnaire, and the score revealed she had moderate depression. She was willing to take an antidepressant but was not interested in psychotherapy. I could have stopped there in my evaluation of her fatigue, but I decided to order some blood tests to see if there was an additional explanation. I asked her to return in two to four weeks.

The customary teaching about medical decision making is based on the principle called Occam’s razor, attributed to 14th-century philosopher William of Ockham. He sought the simplest explanation for a particular phenomenon, one that requires the fewest assumptions. When applied to medicine, this means choosing a diagnosis that accounts for a patient’s symptoms with the simplest explanation. Accordingly, the refrain constantly repeated in my medical school was, “When you hear hoofbeats, think horses, not zebras.” Both patients and doctors prefer having a single diagnosis for a specific problem. Who likes ambiguity?

From my experience, though, as patients get older and more things go wrong, Occam’s razor does not always apply. The counter argument that challenges the simplicity of Occam’s razor is called Hickam’s dictum. This is based on 20th-century physician John Hickam’s assertion: “Patients can have as many diseases as they damn well please.”

In this specific case, Doris’ blood tests revealed she had a second diagnosis: diabetes. When I saw Doris again, her mood had improved, but she was still fatigued. Since fatigue is a common symptom of poorly controlled diabetes, I was not surprised. Other patients with poorly controlled diabetes may have blurred vision, excessive thirst and frequent urination, but apparently fatigue was Doris’ only symptom.

As patients get older and more things go wrong, Occam’s razor does not always apply.

Doris was willing to take medication to control her high blood sugar. In addition, I referred her for diabetes education and to receive instruction about how to monitor her glucose levels. I was feeling optimistic that I had solved her fatigue problem, and I asked her to return in one month.

When Doris returned, she brought her home glucose records showing that her diabetes was well controlled. She felt a little better but was still fatigued! I was dismayed. There had to be yet another explanation. Despite Doris having told me that she slept well, I decided to send her for a sleep study to check for sleep apnea, a condition that results in poor sleep quality because of obstructed nocturnal breathing. From my experience, many people who have this condition think they sleep soundly and are unaware of any problem.

Doris returned to my office a few weeks after her sleep study. The results showed she had severe sleep apnea. In the interim of my seeing her, she had been fitted with a sleep mask to help her obstructed breathing. For the first time in ages, she felt normal. Although Doris ultimately came away with three diagnoses, she was grateful to have her life back.

Managing Doris was a balancing act between choosing Occam’s razor vs. Hickam’s dictum. If I had strictly followed the former, I could have stopped with the diagnosis of depression. Tunnel vision would have resulted in missing the subsequent diagnoses of diabetes and sleep apnea. By contrast, if I had relied only on Hickam’s dictum, I would have subjected Doris to endless costly testing without clear resolution.

As illustrated with Doris, medical decision making can be a challenge. When, as a patient, you don’t seem to be improving as expected, it is reasonable to ask your doctor if there is one diagnosis that accounts for your symptoms — or what additional disorders might be considered. Ideally, your doctor should thoughtfully integrate the principles of Occam’s razor and Hickam’s dictum to provide the best medical care possible.

Dr. Jerry Saliman

Jerry Saliman, MD, retired from Kaiser South San Francisco after a 30-year career and is now a volunteer internist at Samaritan House Medical Clinic in San Mateo.