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ORIGINAL ARTICLES |
From the Department of Psychiatry, University of Toronto, and Sleep Research Laboratory, University Health Network, Toronto Western Hospital (L.K., G. B., R.J., C.M.S.); Toronto Western Research Institute, University of Toronto (L.K., C.M.S.); and Ajax-Pickering General Hospital (K.B.), Pickering, Ontario, Canada.
Dr. Leonid Kayumov, Department of Psychiatry, University of Toronto and University Health Network, Toronto Western Hospital, MP 10-320, 399 Bathurst St., Toronto, ON, M5T 2S8, Canada. Email: lkayumov{at}playfair.utoronto.ca
| ABSTRACT |
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METHODS: Two consecutive overnight polysomnographic recordings were performed on three occasions: at baseline (before treatment), after 4 weeks of melatonin treatment, and after 4 weeks of placebo treatment.
RESULTS: In the 20 patients who completed the study, sleep onset latency was significantly reduced while subjects were taking melatonin as compared with both placebo and baseline. There was no evidence that melatonin altered total sleep time (as compared with baseline total sleep time), but there was a significant decrease in total sleep time while patients were taking placebo. Melatonin did not result in altered scores on subjective measures of sleepiness, fatigue, and alertness, which were administered at different times of the day. After an imposed conventional sleep period (from 24:00 to 08:00), subjects taking melatonin reported being less sleepy and fatigued than they did while taking placebo.
CONCLUSIONS: Melatonin ameliorated some symptoms of delayed sleep phase syndrome, as confirmed by both objective and subjective measures. No adverse effects of melatonin were noted during the 4-week treatment period.
Key Words: melatonin delayed sleep phase syndrome sleep circadian rhythms.
Abbreviations: aMT6s = sulfatoxymelatonin; CES-D = Center for Epidemiologic Studies Depression Scale; DSPS = delayed sleep phase syndrome; HAM-D = Hamilton Depression Scale; REM = rapid eye movement; SOL = sleep onset latency; SSS = Stanford Sleepiness Scale; TST = total sleep time; WASO = wakefulness after sleep onset.
| INTRODUCTION |
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Weitzman et al. (1) reported that 7% to 10% of adults attending sleep disorders clinics had DSPS. A survey of students aged 12 to 20 years found that 16% had chronic difficulty falling asleep and arising in the morning and that 7.3% met the diagnostic criteria for DSPS (4). According to Regestein and Monk (2), within the clinical sleep disorder population DSPS is the most common sleep/wake scheduling disorder observed and accounts for approximately 10% of cases of chronic insomnia.
DSPS is a manifestation of a problem with the physiological timing system of the body clock. The endogenous clock time is controlled by an oscillator located within the hypothalamic suprachiasmatic nucleus. The sleep/wake system depends on the endogenous circadian rhythm of a number of biological parameters, including temperature, hormones, and metabolic parameters. The temporal cue that normally constrains the length of the endogenous circadian period to 24 hours is the ambient light/dark cycle. In some individuals this control system seems to be insufficient. For example, in the blind, those who spend the winter at higher latitudes, and those who have abnormal circadian responses to light stimuli (57), the endogenous period may be insufficiently synchronized to a regular 24-hour cycle using body temperature as a marker of the circadian period.
DSPS is a debilitating condition. It is invariably associated with educational, occupational, financial, social, and marital problems, which may in turn lead to psychiatric problems (1, 2). There seems to be a strong association between DSPS and depression; Regestein and Monk (2) reported that 75% of patients with DSPS seen in a sleep clinic had current symptoms or a history of severe depression, compared with 16% of patients with chronic insomnia but not DSPS and 2% of patients with sleep apnea. The direction of causality between DSPS and depression is unclear. The sleep disturbance in DSPS differs from the sleep disturbance that often accompanies psychiatric disorders, in which it is common to find that once the psychiatric condition is treated the sleep problem diminishes. In DSPS the sleep disruption persists despite treatment for depression. This poor treatment response suggests that DSPS is a cause rather than a consequence of depression.
Despite increased awareness of the prevalence and impact of DSPS, little has been achieved in the way of treatment. Regestein and Monk (2) described the relatively unsuccessful responses to a variety of treatments, including sleep hygiene, chronotherapy, triazolam, and vitamin B12. Chronotherapy is a behavioral technique in which the bedtime is systematically delayed by 3-hour increments each day until the desired bedtime is reached (3, 8, 9). This approach is highly dependent on patient compliance and motivation, resulting in a fairly low success rate; it is not used very much because patients often relapse. Another technique that has been tried in patients with DSPS is bright-light therapy, which has been shown to successfully realign the circadian phase of shift workers (10). Exposure to bright light in the morning and avoidance of light in the evening would be expected to advance sleep onset, but a significant proportion of DSPS patients are not able to wake up before noon and sometimes awaken even later.
Pharmacological approaches to the treatment of DSPS have the potential of being controlled more readily and of increasing patient compliance. One agent of interest is melatonin, which is produced by the pineal gland with a nocturnal peak of secretion during the dark period (1117). Melatonin has been reported to have phase-shifting effects on the sleep/wake cycle (18).
The findings to date regarding melatonin treatment of DSPS are promising but limited. Deacon et al. (19) found that administration of 5 mg of melatonin immediately suppressed core body temperature and increased sleep propensity, suggesting that temperature suppression may play an integral role in phase shifting. Melatonin has been reported to advance sleep onset in patients with DSPS by 82 to 115 minutes (2022). These studies did not include full polysomnographic measures of sleep and involved small numbers of patients. More recently Nagtegaal et al. (23) administered melatonin 5 hours before the individuals "dim-light melatonin onset." Apparently melatonin production is not influenced by sleep and activity and is masked only by bright light. Measuring the onset of melatonin secretion, which is clearly a demarcated event, can be a reliable marker for the circadian phase position. The dim-light melatonin onset has been shown to advance with exposure to bright light in the morning and to delay with exposure to bright light in the evening. A phase-response curve to melatonin in humans is a converse of the phase-response curve to light and is about 12 hours out of phase with the phase-response curve to light (24). In Nagtegaal et al.s study, administration of exogenous melatonin (5 mg) in the evening for 4 weeks caused a predictable (in accordance with the phase-response curve) advance in the onset of the nocturnal melatonin profile of approximately 1.5 hours.
Thus, melatonin seems to be an effective treatment for DSPS. However, prospective studies of large populations of DSPS patients have not been conducted, so treatment remains empirical and intuitive.
The purpose of this study was to investigate the effect of exogenous melatonin on DSPS in a randomized, double-blind, placebo-controlled, crossover trial. A partially fixed time of melatonin administration (from 19:00 to 21:00 hours) was used, allowing patients to adjust themselves to the most beneficial phase-setting effects of the medication. We formulated the following hypotheses: 1) Administration of 5 mg of melatonin at a partially fixed time (early to mid evening) will significantly reduce SOL in DSPS patients during an imposed sleep period time (socially desirable time from 24:00 to 8:00 hours); and 2) Sleep continuity and sleep architecture will be not significantly affected by melatonin.
| METHODS |
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The following exclusion criteria were applied: shift work, presence of other sleep disorders, age <16 years, alcohol or drug abuse, current use of psychotropic medications, active behavioral treatment, and severe psychiatric and neurological disorders. The study protocol was approved by the Human Ethics Committee of the Toronto Hospital, and written informed consent was obtained from all participants after the procedures had been fully explained. All subjects were asked to sign the consent form, confirming that they understood the goals, risks, and potential benefits of the study and their right to withdraw from the study at any time.
The trial was conducted over 9 consecutive weeks during one season (for each patient) to control for seasonal variations in endogenous melatonin levels. Figure 1 illustrates the design of the study. Two consecutive overnight polysomnographic studies were performed at baseline (before treatment) and at the end of 4 weeks of treatment with melatonin and after 4 weeks of treatment with placebo. Polysomnographic results obtained on the first night on each occasion were not included in the analysis to avoid a possible "first-night" effect (28). For the baseline recordings, patients chose their own retiring and wake up times as consistent with their normal routine. After the second baseline night, patients were randomly assigned to either the placebo or melatonin group. Each subject then received either 5 mg/d of melatonin or placebo (of identical appearance) for 4 weeks. The order of treatment was randomized, and no effects of order were noticed (the order of treatment was accounted for as a blocking factor). Both melatonin and placebo capsules were supplied by Penn Pharmaceutical Limited (Edinborough, UK). The medication (melatonin or placebo) was taken at 19:00 hours during the first week, between 19:00 and 21:00 hours during the second and third weeks (according to the patients preference), and at a consistent time chosen by the patient during the fourth week. The mean time chosen by patients taking melatonin was 21:03 ± 5.7 (the second value represents standard deviation in minutes); the mean time chosen by those taking placebo was 20:57 ± 9.2 (p > .05). At the end of each 4-week treatment phase, two consecutive overnight polysomnographic recordings were made during the imposed sleep period (24:00 to 08:00 hours). There was a washout period of 1 week between the two treatment phases.
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Urine samples for sulfatoxymelatonin (aMT6s) measurements were collected on the 27th day of both placebo and melatonin treatment during the 24-hour period at four times: from 21:00 to 24:00 hours, from 24:00 to 08:00 hours, from 08:00 to 15:00 hours, and from 15:00 to 21:00 hours. Urine was collected under dim-light conditions during the dark period. Urine was not collected at baseline because the patients were allowed to follow their habitual routine (eg, watch TV, read, or work at late hours) and light exposure was not controlled. Immunoassays to determine the concentration of aMT6s in urine were performed according to the methods described by Aldhous and Arendt (30) using a commercial kit (CIDtech Research Inc., Mississaug, Ontario, Canada).
Before retiring to bed on the second night of each phase of the trial, patients completed the Toronto Alexithymia Scale (31, 32), a standard presleep questionnaire; the SSS (33); a seven-item Fatigue Scale; and a newly developed seven-item alertness scale, ZOGIM-A (34). On the following morning, immediately after awakening, each patient completed a standard postsleep questionnaire, the SSS, and the Fatigue Scale. Approximately 20 minutes after awakening, patients assessed their level of fatigue and sleepiness using the following scales: the Fatigue Severity Scale, the Epworth Sleepiness Scale (35), the Toronto Western Hospital Fatigue Questionnaire, the Fatigue Scale, and the FaST Adjective Checklist. The total results were reported as a composite fatigue score, which has been validated in studies on patients with multiple sclerosis (36).
After completing fatigue questionnaires, patients were asked to complete a complex verbal reasoning task (37, 38). Accuracy and time required to complete the test were assessed. To evaluate subjective circadian profiles of sleepiness, fatigue, and alertness, the patients were asked to complete the SSS, the Fatigue Scale, and the seven-item alertness scale at 2-hour intervals throughout the day starting approximately half an hour after the final awakening. This protocol was used as a substitute of the standard Multiple Sleep Latency Test (39) and Maintenance of Wakefulness Test (40) after each overnight polysomnographic study.
One-way analysis of variance was used to determine the statistical significance of sleep variables and subjective scores for the three nights from each phase of the trial. Statistically significant results detected by analysis of variance (p < .05) were further analyzed by using Tukey post hoc paired comparisons using the Statistical Package for the Social Sciences software (SPSS for Windows). Results in the text are expressed as mean ± standard deviation.
| RESULTS |
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Objective and subjective parameters obtained in the sleep clinic in all phases of the trial are shown separately for convenience. The results of the objective measures, namely the polysomnographic sleep variables, have been separated into three categories: sleep continuity, sleep architecture, and REM sleep. Differences in sleep data at baseline, while taking placebo, and while taking melatonin are shown in Table 1.
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Results of the subjective assessments of sleepiness, fatigue, and alertness are presented in Table 2.
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There was also no significant difference in performance on the verbal reasoning task at baseline or with melatonin or placebo treatment.
We examined the association between excretion of aMT6s and objective and subjective measurements of sleep in patients with DSPS. During placebo treatment, absolute values of aMT6s excreted in urine were low, but the pattern of secretion was normal.
The repeated-measures procedure revealed a robust circadian pattern of aMT6s excretion (F = 15.3; p = .0001) in 15 of the 20 patients. There was a significant increase of nocturnal aMT6s excretion in the urine collected between 24:00 and 08:00 hours while taking placebo ( Figure 2) compared with excretion of the melatonin metabolite between 21:00 and 24:00 hours (2.9 ± 6.3 vs. 24.8 ± 38.3 nmol, p = .02). A significant decrease of aMT6s excretion during the day from 08:00 to 15:00 hours toward evening hours from 15:00 to 21:00 hours was observed (8.5 ± 8.6 and 3.0 ± 3.5 nmol; p = .05 and p = .006, respectively). Five of the 20 patients showed an abnormal circadian pattern of melatonin secretion while receiving placebo treatment ( Figure 3). Their peak excretion of aMT6s did not occur at night, as would normally be expected, but between 08:00 and 15:00 hours. These five patients had the most severe symptoms of DSPS. In three of these five patients, exogenous melatonin treatment normalized the pattern of excretion with the nocturnal peak and daytime decrease in the level of excreted aMT6s.
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| DISCUSSION |
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By conventional analysis of our data, we did not find any significant differences in sleep architecture measured at baseline, melatonin treatment, and placebo administration. The standard sleep variables (sleep efficiency, WASO, percentage of sleep stages, etc.) were marked by large interindividual variability and therefore lack the inherent sensitivity to express the intrinsic polysomnographic features.
A salient feature of our study design was allowing patients to select their baseline bedtime and duration of sleep. This strategy permitted us to compare their natural sleep pattern with that of the imposed sleep period (from 24:00 to 08:00 hours) while receiving treatment with melatonin or placebo. Our goal was to evaluate whether melatonin would provide the same or better quality and quantity of sleep in an imposed, socially desirable regimen of the sleep/wake cycle compared with the sleep obtained with the usual delayed regimen that these patients have. Our study failed to reveal any significant difference in TST at baseline and after melatonin treatment (notwithstanding the imposed bedtime in the latter condition). There was a significant decrease in TST after placebo treatment compared with baseline (p = .006). Thus, sleep at a phase-advanced, more socially acceptable time was normal in architecture and similar to the phase-delayed sleep of this study group.
In their recent study, Nagtegaal et al. (23) administered melatonin 5 hours before the onset of the evening rise of endogenous melatonin, based on the so-called "dim-light melatonin onset" (47). The authors themselves questioned whether this individualized timing resulted in better clinical effects compared with fixed times of melatonin administration. The partially fixed regimen used in our study allowed patients the flexibility to adjust the phase-setting actions of melatonin. The self-selected timing regimen seems to result in better patient compliance and may be more cost-effective in clinical settings. Furthermore, our findings, which are based on polysomnographic and subjective assessments of sleep, fatigue, alertness, and performance, support a successful entrainment of our patients with DSPS to the socially desirable time of sleep/wake cycle.
Numerous studies have confirmed the nocturnal rise of melatonin production and decline during the daytime in healthy people (7, 15, 17, 18). However, there are no published absolute normative values for aMT6s, and age and sex variations still need to be established (Brown GM, 1999, personal communication). Sack et al. (48) showed that aMT6s decreases with age; however, a recent study by Zeitzer et al. (49) did not support the hypothesis that a reduction in the plasma concentration of melatonin is a general characteristic of healthy aging. There has been considerable debate about the effect of exogenous melatonin on the circadian timing system of endogenous melatonin secretion (50). Although our results do not answer this question per se, we observed a normalization of the circadian pattern of excreted aMT6s after oral administration of 5 mg of melatonin in three of five DSPS patients who had abnormal melatonin production while taking placebo. These five patients showed peak melatonin excretion between 08:00 and 15:00 hours, and they had the most severe symptoms and manifestations of DSPS as confirmed by both objective and subjective measurements (inability to initiate sleep before 04:0006:00 hours, loss of employment, and symptoms of comorbid depression). The other 15 patients had the usual nocturnal rise in melatonin production while taking placebo.
Administration of 5 mg of melatonin caused a rapid increase in the amount of excreted aMT6s with the peak during nocturnal hours. Large interindividual differences in excreted aMT6s were observed. The rapid decline of aMT6s from 08:00 to 15:00 hours may explain why our patients did not report any hangover effects, as judged by the subjective assessments of the circadian pattern of sleepiness, fatigue, and alertness. These findings are consistent with previous reports on the effects on the following day (21).
In conclusion, melatonin was an effective treatment for patients with DSPS, as confirmed by both objective and subjective measures. No adverse effects of melatonin were noted during the 4 weeks of treatment. The "phase-advanced" sleep during melatonin treatment significantly decreased SOL compared with placebo but did not alter sleep architecture from that of phase-delayed sleep. However, more controlled observations are required to determine the intrinsic mechanisms involved in the chronobiotic effects of melatonin in DSPS. Dose-response relationships, consequences of long-term use, and the possibility of relapse after discontinuation of melatonin treatment remain to be explored.
Received for publication January 4, 2000.
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