National Sleep Foundation Statement in Response to Archives of General Psychiatry Article

2/14/2002

From: Marcia C. Stein of the National Sleep Foundation, 202-347-3471, ext. 205; e-mail: Mstein@sleepfoundation.org

WASHINGTON, Feb. 14 -- Following is a National Sleep Foundation statement in response to the Archives of General Psychiatry article, "Mortality Associated With Sleep Duration and Insomnia" (February 2002):

The Kripke et al. data and conclusions, that there is little mortality risk associated with short sleep and insomnia, have the potential of causing the public unnecessary confusion and concern. The fact that the same issue of the Archives of General Psychiatry contains a commentary that cautions against over-interpretation of the data indicates that at least some scientists, and the journal, recognize the limitations of the Kripke et al. data and the potential for confusion. We urge people interested in this article to also read the commentary by Buysse and Ganguli, as well as to consider the following:

Although the study reports data that is of interest, limitations in the study methodology restrict the conclusions that can be reached, particularly about the amount of sleep needed to sustain an individual's health, safety and well-being. The database used in the article was simply not designed to answer the questions asked, and clearly cannot be used to establish cause and effect relationships. The following limitations restrict the conclusions to be drawn from these data:

-- Although sizeable, the study population (friends and relatives of American Cancer Society volunteers) is not a random sample and doesn't represent the entire population. Geographic, racial and other factors of the study group are not indicated. Indeed, the authors question the validity of the sample by stating that the overall death rate of their sample was quite different from that of the general population.

-- By only asking only a single question about sleep duration, the estimates of daily sleep time are likely to represent typical workweek sleep (at least for those employed) and to exclude weekend sleep and daytime naps. According to National Sleep Foundation polls, adults sleep more on weekends than weeknights, (7.8 hours/night vs. 7.0 hours/night). Thus, actual daily sleep times may be higher than those reported by survey respondents in this article.

-- By not using a standardized definition of "insomnia," respondents used their own subjectively determined or unique definition of the problem.

-- Similarly, patient self-report for use of "sleeping pills" was not validated or controlled so that any type of product or medication the respondent thought of as a "sleeping pill" was included as a positive response. Additionally, such medications used between 1980-1986, when the study was conducted, are different from those in use today; the data reflected in this article may unduly alarm current users of these medications. Moreover, people who use sleeping pills are likely to be the most severely affected insomniacs, both in terms of insomnia itself, but also in terms of other illnesses (since insomnia commonly is a result of other illnesses). Attributing mortality to use of sleeping pills per se would be an error.

As Drs. Buysse and Ganguli note in their commentary, "short sleep duration and insomnia can be bad for you, even if they are not associated with early death." There are many scientific investigations which have documented negative consequences or correlates of both:

-- insomnia -- e.g., increased risk of depression; problems with memory, family/social relationships and mood; poorer quality of life; increased health care costs; increased absenteeism; increase risk for coronary disease; and hyperarousal.

-- insufficient sleep -- e.g., excessive sleepiness; negative mood changes; reduced performance on standardized tasks; increased accident risk; and acute negative effects on glucose metabolism and immune function.

Thus, even if short and long sleep durations are statistically related to mildly increased mortality risk, and even if insomnia is not related to increased mortality risk, there are many reasons to continue to urge people to obtain adequate sleep and to discuss insomnia with their doctor. Mortality is not the only important outcome measure.

The National Sleep Foundation emphasizes that substantial research serves as the basis for the recommendation that adults obtain an average of seven to nine hours of sleep each night, recognizing that each person has an individual requirement for his/her own amount of sleep. If someone sleeps 8.5 hours a night and feels alert and energetic, it would be incorrect to reduce sleep time based on the Kripke article.

The National Sleep Foundation also urges patients and physicians to give greater attention to sleep. Too much or too little sleep may signal serious health problems that should be discussed with a physician. Patients should report to their doctors about the quantity and quality of sleep, and whether they experience daytime sleepiness, insomnia, snoring, pauses in breathing, or excessive movements during sleep.