Maintenance of wakefulness test: A polysomnographic technique for evaluating treatment efficacy in patients with excessive somnolence ☆

Ten male subjects were studied for a total of 306 days on self-selected schedules Four of them developed bedrest-activity cycle period lengths very different from 24 hr (mean = 368 hr) despite the persistence of near-24-hr oscillations in other physiologic functions, including that of body temperature (mean = 246 hr) The percentage of sleep time spent in REM sleep varied significantly with the phase of that near-24-hr body temperature cycle The peak in REM sleep propensity (RSP) occurred on the rising slope of the average body temperature curve, coincident with the phase of peak sleep tendency This was associated with a significantly increased REM episode duration and shortened REM latency (including sleep-onset REM episodes), but without a significant change in the REM-NREM cycle length We conclude that there is an endogenous circadian rhythm of REM sleep propensity which is closely coupled to the body temperature rhythm and is capable of free-running with a period different from both 24 hr and the average period of the sleep-wake cycle

Timing of REM sleep is coupled to the circadian rhythm of body temperature in man.

The multiple sleep latency test (MSLT) was first used at the Stanford Sleep Laboratory in the spring of 1976 in a validation sleep-loss study, and the data were presented at the 1977 Associated Professional Sleep Societies (APSS) meeting.1 The success of that initial study and the desire to learn more about the measure led to the inclusion of the MSLT as a core measure for the Stanford Summer Sleep Camp experiments carried out over the next 10 years. These experiments included the longitudinal assessment of adolescent sleep, as well as a number of studies in which sleep quantity was manipulated, studies in normal elderly persons, and evaluations of patients with narcolepsy and sleep apnea syndrome. These Sleep Camp experiments began in the summer of 1976, and the 1977 APSS meeting also included early reports of MSLT in 10to 13-year-old adolescents under baseline conditions2 and following a night of acute sleep restriction.3 The following summer’s study of the adolescent participants included Tanner staging of pubertal development, and the first report of MSLT as a function of developmental stage in this cohort was presented at the 1978 APSS meeting.4 The 1980 report in SLEEP reprinted for this anniversary issue5 summarized baseline sleep and MSLT data from the first 3 years of the Stanford longitudinal adolescent study. This project was an important part of Carskadon’s doctoral dissertation,6 completed with the mentorship of a committee comprising William C. Dement, MD, PhD; Helena Chmura Kraemer, PhD; and Thomas F. Anders, MD. Dr. Kraemer’s influence is most apparent in the survival-curve analysis of the MSLT data for the dissertation and the 1980 paper. The survival-curve approach remains among the best but most underused methods for analyzing MSLT data, although a resurgence of this approach has recently emerged.7 In terms of visual display of the data, the survival curves are superior to virtually every other method because they show every data point in the sample. At the same time, however, the survival-curve displays are somewhat inefficient and do not always clearly convey patterns that may be important. Most subsequent studies with MSLT have used a variety of other analysis and display techniques, including simple median and mean and log transform. In rereading the 1980 paper,5 several methodologic features stand out. In the first place, this study was a major departure from previous evaluations of normal sleep: sleep schedules were fixed not only during the recording nights, but also for 1 week before in-lab visits and for all the follow-up evaluations. Most sleep studies (either longitudinal or cross sectional) in the 1960s and 1970s evaluated sleep in the context of subjects’ “usual schedules.” Second, this study was one of the first polysomnographic examinations of human sleep in a 24-hour context, giving equal weight to evaluating the sleeping and waking portions of the day. In contrast to earlier 24-hour sleep-wake studies that used alternative sleep schedules, such as the 240-minute schedule,8 the 180minute day,9 or the 90-minute day,3,10 this project attempted to examine waking alertness in the context of optimal nighttime sleep. [These innovations came from a collaborative effort of Carskadon and her dissertation advisers: Tom Anders was interested in learning about the “sleepy child” and Bill Dement was interested in sleepiness per se. They determined that a basal protocol run in normal children, stabilizing scheduled sleep at a level that appeared adequate for younger participants, was fundamental to both goals. The collaboration provided Carskadon great latitude in the design and implementation of the protocol: what a wonderful research opportunity for a graduate student!] Another striking feature of the 1980 paper was the discussion’s extensive apologia of the MSLT as a valid measure of sleepiness. Although the MSLT had been in use for several years and a number of publications had appeared,11-13 many scientists remained skeptical about the MSLT’s utility. This skepticism continued for a number of years. In 1986, however, the American Sleep Disorders Association recognized the importance and usefulness of the MSLT by convening a committee to prepare guidelines for its use.14 Data collection from this cohort of normal youngsters continued for a total of six summers, and more of the data were included in two subsequent summaries of the findings. Carskadon’s 1982 chapter in Guilleminault’s book on indications and techniquesa provided summary tables by Tanner stage of the nocturnal sleep and daytime MSLT data for each of the three study days.16 Data from a comparison group of young adults who had been studied under similar conditions were also included in that chapter. (Similar summary tables for children aged 8 and 9 years appeared in a subsequent publication.17) Preliminary data from a small sample of children with a family history of narcolepsy who were followed along with the normal adolescent sample were included in the 1982 chapter. Carskadon and colleagues published the final summary of the longitudinal data in another book chapter,18 which presented the data from all 6 years of the longitudinal study and provided tables and formulas for determining values of sleep and MSLT by age, sex, and Tanner stage. These tabled data were used as the context for interpreting findings from the cohort of adolescents with a family history of narcolepsy.

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Regulation of sleepiness in adolescents: update, insights, and speculation.

▪ Abstract Evidence that the sleep-wake rhythm is generated endogenously has been provided by studies employing a variety of experimental paradigms such as sleep deprivation, sleep displacement, isolating subjects in environments free of time cues, or imposing on subjects sleep-wake schedules widely deviating from 24 hours. The initial observations obtained in isolated subjects revealed that the period of the endogenous circadian pacemaker regulating sleep is of approximately 25 hours. More recent studies, however, in which a more rigorous control of subjects' behavior was exerted, particularly over lighting conditions, have shown that the true periodicity of the endogenous pacemaker deviates from 24 hours by a few minutes only. Besides sleep propensity, the circadian pacemaker has been shown to regulate sleep consolidation, sleep stage structure, and electroencephalographic activities. The pattern of light exposure throughout the 24 hours appears to participate in the entrainment of the circadian pacemak...

Sleep-wake as a biological rhythm.

One hundred thirty sleep episodes of 6 subjects, living on a natural 24 hr day, were compared with 116 sleep times of the same subjects living isolated from external time cues The polygraphic sleep recordings were analyzed for the distribution of REM sleep under both conditions Additionally, the relationship between body temperature and REM sleep was analyzed by comparing sleep episodes in which the temperature minimum occurred early in the sleep episode with those in which there was a late temperature minimum The results show that there is more REM sleep in the beginning of sleep in sleep episodes of free-running rhythms as compared to sleep episodes of entrained 24 hr rhythms This higher amount of REM sleep is due to a longer first REM episode and shorter first NREM episodes The comparison of the sleep episodes that differ in the position of the temperature minimum shows similar differences, ie, more REM sleep in the beginning of sleep episodes in which the temperature minimum occurs earlier as compared to episodes in which the temperature minimum occurs later It was hypothesized that the amount of REM sleep depends on the phase relationship between sleep and the circadian temperature cycle From this point of view, the difference in the distribution of REM sleep in the entrained 24 hr rhythm, on the one hand, and the free-running rhythm, on the other hand, can be explained by the different courses of body temperature during sleep That only the first REM episode is influenced by circadian parameters may indicate an exceptional role for this REM episode in contrast to the following episodes

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J.M Moses

Papers

Dynamics of nap sleep during a 40 hour period