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Abstract & commentary
Synopsis: Excessive daytime sleepiness is associated progressively with snoring frequency.
Source: Gottlieb DJ, et al. Am J Respir Crit Care Med 2000; 162:1512-1517.
The sleep heart health study is an ongoing, multicenter investigation into the cardiovascular consequences of sleep-disordered breathing.1 In this study, 5777 participants (mean age 64, 53% women) were divided into four groups based on Respiratory Disturbance Index (RDI), which is essentially the same as Apnea plus Hypopnea Index (AHI). As expected, sleepiness, assessed by total Epworth Sleepiness Score (ESS), increased with increasing RDI. The mean ESS in subjects with the lowest (< 1.5 events/h) RDI was 7.1, and the ESS for those with the highest (> 30) RDI was 9.7 events per hour. Subjects were also classified by responses to the question, "Have you ever snored?" For those who answered yes, snoring was quantified as not current (or unknown), less than one night per week, 1-2 nights per week, 3-5 nights per week, or 6-7 nights per week. Sleepiness (defined as a total ESS of 11 or more) increased progressively with snoring frequency. Eighteen percent of those with snoring less than one night per week, compared with 39% of those reporting snoring six or seven nights per week, met the definition of "sleepy" used in this study. Snoring was strongly associated with RDI of course, but analysis of variance indicated that snoring is an independent risk factor for sleepiness. Sleepiness also correlated with male gender, increasing age, endorsement of leg cramps "often" or "almost always," and the difference of the usual total sleep time on weekends minus usual total sleep time on weekdays. It was inversely related to self-reported total sleep time on week nights.
Comment by Barbara A. Phillips, MD, MSPH
The Epworth Sleepiness Scale2 is a deceptively simple tool that is the most commonly used measure of sleepiness in clinical practice. (See Table.)
|Table-The Epworth Sleepiness Scale|
|How likely are you to doze off or fall asleep in the following situations,
in contrast to just feeling tired? This refers to your usual way of life in
recent times. Even if you have not done some of these things recently, try
to work out how they would have affected you. Use the following scale
to choose the most appropriate number for each situation: 0 = would
never doze; 1 = slight chance of dozing;
2 = moderate chance of dozing; and 3 = high chance of dozing.
|Situation||Chance of Dozing|
|Sitting and reading||_____|
|Sitting, inactive, in a public place||_____|
|As a passenger in a car for an hour||_____|
|Lying down in the afternoon||_____|
|Sitting and talking to someone||_____|
|Sitting quietly after a lunch without alcohol||_____|
|In a car, while stopped for a few minutes in traffic||_____|
Critics of this tool cite its subjective nature and weak correlation with objectively measured sleepiness. However, the ESS has good test-retest reliability and internal consistency.3 It has previously been shown to correlate with RDI,4 with response to treatment of sleep-disordered breathing,5 to the likelihood of falling asleep while driving6 and to quality of life.7 Most importantly, it is easy and rapid to use. An even simpler assessment of sleepiness was recently reported to predict automobile crashes. Drivers who reported becoming so sleepy while driving that they feared falling asleep one out of three times that they drove on a highway had 10 times the rate of automobile crashes as those who did not.8 The fact that sleepiness is a risk factor for automobile accidents escalates the problems from one of personal to public health.
Like pain, depression, and pornography, self-reported sleepiness is subjective, which makes it difficult to define and to measure. While we are uncomfortable with imprecise and subjective measures, there is little doubt that they can have significant effects on human life.
That sleepiness is associated with snoring should not surprise us. Snoring has previously been reported to be associated with hypertension,9 pregnancy risk,10 and, of course, sleep apnea.
There are many take home messages from this paper. We need to query our patients about sleepiness, especially while driving. It might be good to include the ESS in a questionnaire of general health screening. Snoring is not necessarily a benign symptom. And, most of us need to get more sleep.
1. Quan SF, et al. Sleep 1997;20:1077-1085.
2. Johns MW. Sleep 1991;14:540-545.
3. Johns MW. Sleep 1994;15:376-381.
4. Bennett LS, et al. Am J Respir Crit Care Med 1998; 158:778-786.
5. Engleman HM, et al. Am J Respir Crit Care Med 1999; 159:461-467.
6. Maycock G. Accid Anal Prev 1997;29:453-462.
7. Briones B, et al. Sleep 1996;19:583-588.
8. Masa JF, et al. Am J Respir Crit Care Med 2000;162: 1407-1412.
9. Bixler EO, et al. Arch Intern Med 2000;160:2289-2295.
10. Franklin KA, et al. Chest 2000;117(1):137-141.