Nocturnal Determinants of Daytime Sleepiness

Mary A. Carskadon, William C. Dement
1982 Sleep  
In the previous paper (1), we discussed a number of factors that contribute to the manifestation of physiological sleep tendency. In this paper, we shall describe factors that determine the level of this physiological tendency. In general, we feel that there are two major factors that account for physiological sleep tendency at any given time in normal individuals: phase of the circadian rhythm, which will be discussed in several other papers in this issue, and prior sleep history, that is, the
more » ... story, that is, the amount and "quality" of sleep. It seems clear that these two factors are interdependent: a change in circadian phase may disrupt nocturnal sleep, and restricting or displacing sleep may alter circadian systems. Thus, although there is no clearcut dichotomy between the two factors, we have focused on changes within a night or several nights of sleep that appear largely responsible for significant changes in daytime sleepiness. U sing the Multiple Sleep Latency Test (MSLT) as our chief dependent variable, we have performed a number of experimental manipulations of sleep in young adult volunteers. Most of these studies have had a similar structure: the level of daytime sleepiness was tested during basal conditions, after manipulating sleep, and after a return to baseline conditions. The studies have evaluated prolonged basal conditions, in addition to the effects of sleep extension, acute and prolonged sleep restriction, and sleep deprivation. All MSL T scores reported here were taken from daytime tests (usually 0930-1930) performed at 2-h intervals with a 20-min cutoff. Basal sleep schedule Basal sleep tendency was evaluated in six young adults (three women, three men; ages 18-23 years, mean age = 20.2) who lived on a fixed schedule for 7 consecutive days. The subjects reported habitual sleep times of 7.5 -8 h a night and were not habitual nappers. Bedtime each day was midnight, arising time was 0800, and MSLTs were performed in the standard manner beginning at 0930 each day. Data from this study provide an excellent opportunity to examine questions
doi:10.1093/sleep/5.s2.s73 fatcat:taq7zgbjl5h6nkfiuvvnkd5d4e