26 August 2012

Harrison's Ch. 27: "Sleep Disorders"

Note: While I attempt to read the 397 chapters of Harrison's Principles of Internal Medicine, I am writing occasional reflections.  

From Harrison's Ch. 27 ("Sleep Disorders"):
Driving is particularly hazardous for patients with increased sleepiness. Reaction time is equally impaired by 24 h of sleep loss as by a blood alcohol level of 0.10 g/dL. More than half of Americans admit to having fallen asleep while driving. An estimated 250,000 motor vehicle crashes per year are due to drowsy drivers, causing about 20% of all serious crash injuries and deaths....

Failure to recognize and treat [sleep apnea] appropriately may lead to impairment of daytime alertness, increased risk of sleep-related motor vehicle accidents, hypertension and other serious cardiovascular complications, and increased mortality. Sleep apnea is particularly prevalent in overweight men and in the elderly, yet it is estimated to remain undiagnosed in 80–90% of affected individuals. This is unfortunate since effective treatments are available.

Traditionally, doctors and patients haven't given terribly much thought to the health impact of the third or so of our lives we spend in bed. But as we become more overweight (causing sleep problems) and as we better understand the health burden of sleep problems, perhaps there will be a renewed focus on sleep.

When I was seeing patients in a primary-care clinic, I asked some of them whether they felt well-rested during the day. Most said they were sleepy all the time. When I then administered the Epworth Sleepiness Scale, a standard test to assess risk for sleep apnea, some of the results were startling. One patient scored a 21 out of a possible 24, with 9 being the cutoff for urgent referral to a sleep expert. Patients were falling asleep during business meetings and while driving. I dutifully referred them for a home sleep study. I regret not having asked more patients about their sleeping habits, because I'm sure that many of them had undiagnosed sleep apnea. I vividly recall years ago hearing a sleep expert call sleep apnea a "walking time bomb."

I also saw a handful of patients who had been diagnosed with sleep apnea and who were on treatment (typically CPAP, a mask worn at night that supplies air). They said they felt like new people.

I recently came across the excellent "Anonymous Doc" blog, written by a medical resident. He writes about a time he was very sleepy.

Harrison's discusses the phenomenon of tired medical residents in the chapter:
Resident physicians constitute another group of workers at risk for accidents and other adverse consequences of lack of sleep and misalignment of the circadian rhythm. Recurrent scheduling of resident physicians to work shifts of 24 h or more consecutive hours impairs psychomotor performance to a degree that is comparable to alcohol intoxication, doubles the risk of attentional failures among intensive care unit interns working at night, and significantly increases the risk of serious medical errors in intensive care units, including a fivefold increase in the risk of serious diagnostic mistakes. Some 20% of hospital interns report making a fatigue-related mistake that injured a patient, and 5% admit making a fatigue-related mistake that results in the death of a patient. Moreover, working for >24 h consecutively increases the risk of percutaneous injuries and more than doubles the risk of motor vehicle crashes on the commute home.