The study population includes healthy adults in early middle age. We also examine the extent to which a single-day report of how much a person slept the previous night reflects measured sleep for that night. In this study we estimate the extent to which self-reports of usual sleep hours reflect an average of objectively measured sleep durations. There has been little validation of such questions relative to more objective measures of sleep. Many of the epidemiologic investigations to date have mined established cohorts that included a survey question such as “How many hours of sleep do you usually get a night (or when you usually sleep)?” ( 1). In a sleep laboratory, hours available for sleep are carefully controlled, and sleep is precisely monitored through polysomnography. Sleep, though, is measured differently in experimental sleep laboratory studies than it is in most epidemiologic studies. Thus sleep duration has become a potentially important and novel risk factor for chronic disease. These studies have in part been motivated by exciting findings from sleep laboratory studies that have demonstrated reduced sleep hours produce short-term metabolic and hormonal derangements, notably impaired glucose tolerance and increased appetite ( 14- 16). Recent epidemiologic studies have found that sleep duration is associated with obesity, diabetes, hypertension and mortality ( 1- 13). Although asking about sleep duration seems uncomplicated, the correlation between self-reported and objectively-measured sleep in this population was moderate and systematically biased. The extent of overestimation, calibration and correlation varied by personal and sleep characteristics. Overall, there was a correlation of 0.45 between reported and measured sleep duration. Our model suggests that persons sleeping 5 and 7 hours over-reported, on average, by 1.3 and 0.3 hours respectively. Subjective reports were not well calibrated, increasing on average by 31 minutes for each additional hour of measured sleep. Average measured sleep was 6 hours, and subjective reports averaged 0.80 hours longer than measured sleep. Sleep measurements collected in two waves included: 3-days of wrist actigraphy, a sleep log, and standard questions about usual sleep duration.
Eligible participants at the Chicago site of Coronary Artery Risk Development in Young Adults Study were invited to participate in a 2003-2004 ancillary sleep study 82% (n=669) agreed. We model the extent to which self-reported habitual sleep reflects average objectively measured sleep. These studies have used self-reported habitual sleep duration, which has not been well validated. Recent epidemiologic studies have found that sleep duration is associated with obesity, diabetes, hypertension and mortality.
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