The American Journal of Medicine
Volume 116, Issue 2 , Pages 91-95, 15 January 2004

Nocturnal 6-sulfatoxymelatonin excretion in insomnia and its relation to the response to melatonin replacement therapy☆

  • Damien Leger, MD

      Affiliations

    • Centre du Sommeil (DL), Hotel-Dieu de Paris, Paris, France
    • ,
  • Moshe Laudon, PhD

      Affiliations

    • Neurim Pharmaceuticals Ltd (ML, NZ), Tel Aviv, Israel
    • ,
  • Nava Zisapel, PhD

      Affiliations

    • Corresponding Author InformationRequests for reprints should be addressed to Nava Zisapel, PhD, Department of Neurobiochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
    • Neurim Pharmaceuticals Ltd (ML, NZ), Tel Aviv, Israel
    • Department of Neurobiochemistry (NZ), Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel

Received 18 November 2002; accepted 9 September 2003.

Article Outline

Abstract 

Purpose

Melatonin, which is produced by the pineal gland at night, is an endogenous sleep regulator. Both sleep disorders and impaired melatonin production are common among the elderly. We examined the excretion of the major melatonin metabolite 6-sulfatoxymelatonin in insomnia patients aged ≥55 years and its relation with the subsequent response to melatonin therapy.

Methods

We studied 517 insomnia patients, along with 29 age-matched and 30 younger healthy volunteers. Nocturnal urinary 6-sulfatoxymelatonin excretion was assessed between 10 pm and 10 am. Three hundred and ninety-six of the insomnia patients were treated for 2 weeks with placebo and for 3 weeks with 2 mg per night of controlled-release melatonin, of which 372 provided complete datasets. Clinical response, assessed with the Leeds Sleep Evaluation Questionnaire, was defined as an improvement of 10 mm or more on the visual analog scales.

Results

Mean (± SD) 6-sulfatoxymelatonin excretion was lower in the insomnia patients (9.0 ± 8.3 μg per night) than in volunteers of the same age (18.1 ± 12.7 μg per night, P <0.05) and in younger volunteers (24.2 ± 11.9 μg per night, P <0.05). About 30% of patients (112/372) excreted ≤3.5 μg of sulfatoxymelatonin per night, which is considered to be lower than normal for this age group. These “low excretors” had a significantly higher response to melatonin replacement therapy (58% [65/112] vs. 47% [122/260], P <0.05).

Conclusion

Low nocturnal melatonin production is associated with insomnia in patients aged 55 years or older, and identifies patients who are somewhat more likely to respond to melatonin replacement.

 

Primary insomnia is characterized by difficulty initiating or maintaining sleep for at least 1 month that distresses the patient or impairs daytime functioning. About 30% of persons aged 65 years or older have insomnia 1, 2, 3, 4, 5, 6. Because complaints about poor sleep do not correlate well with objective findings 7, 8, the diagnosis of insomnia and the clinical assessment of treatment effects are based on self-report.

Melatonin (N-acetyl-5-methoxytryptamine) is produced and secreted by the pineal gland at night, and promotes sleep in humans (9). It is metabolized rapidly in the liver. Urinary excretion of its major metabolite—6-sulfatoxymelatonin—is a useful measure of the total amount of melatonin produced (10). Peak serum levels of melatonin at night, as well as 6-sulfatoxymelatonin excretion, decrease significantly with advancing age 11, 12, 13, 14, 15, although these age-related declines are less pronounced in healthy subjects 16, 17. Several studies have suggested a possible association between age-related disturbances in the sleep-wake cycle and this decrease in melatonin output 16, 18, 19, 20, 21, but other studies have found similar age-related decline in melatonin production in good and in poor sleepers 22, 23.

If melatonin deficiency is a cause of insomnia, patients with low melatonin levels should be more likely to benefit from melatonin therapy than those with normal levels. Some 24, 25, 26, 27, 28, 29 but not all 30, 31, 32 studies have demonstrated beneficial effects of melatonin on sleep in insomnia patients aged 55 years or over and in patients who presumably had low production of melatonin. These studies varied in their inclusion criteria and most had only a relatively small number of subjects. We therefore assessed 6-sulfatoxymelatonin levels in a large cohort of well-characterized insomnia patients aged 55 years or over, and determined the relation between 6-sulfatoxymelatonin excretion and subsequent improvement in sleep after melatonin replacement therapy.

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Methods 

Subjects 

Patients (330 men, 187 women) aged 55 years or over (mean [± SD] age, 68 ± 8 years; range, 55 to 93 years) with primary insomnia according to standard criteria (33) were recruited from general medical clinics in France, Israel, and The Netherlands from 1995 to 1998. Patients were excluded if they had symptoms of anxiety (Covi scale 34), depression (Raskin scale 35), or senile dementia (MINI 36), or had a history of a severe psychiatric disorder. Of these patients, 172 (age, 65 ± 6 years) were healthy and 345 (age, 69 ± 9 years) had one or more chronic medical problems.

We also enrolled two groups of healthy volunteers without sleep complaints: a younger group comprising subjects aged 20 to 35 years (n = 30; all men; mean age, 27 ± 2 years) and an older group comprising subjects aged ≥55 years (n = 29; 13 men and 16 women; mean age, 67 ± 6 years). These patients had been recruited for pharmacokinetic and drug interaction studies. The number of healthy volunteers was small compared with the number of patients because the excretion of 6-sulfatoxymelatonin in healthy subjects has been studied extensively 15, 22, 23, 37, 38, 39, 40 and our results were compatible with the published data.

All subjects could not have used any psychoactive medication for at least 1 month before the study. The study protocols had been approved by the local ethics or human subjects committees; and all subjects were informed in detail about the investigation and gave written informed consent.

Measurements 

Urine was collected at night (10 pm to 10 am) and during the day (10 am to 10 pm) while at home. To enhance compliance, no specific instructions were given about lighting conditions while sleeping. Urinary 6-sulfatoxymelatonin levels were determined by radioimmunoassay (41). Patients and their physicians were not provided the results of these tests.

Of the 446 insomnia patients who were recruited in France, 396 were treated with placebo tablets for 2 weeks (once daily, between 9 and 11 pm), followed by tablets of identical composition and appearance containing 2 mg of melatonin (Circadin, controlled-release formulation; Neurim Pharmaceuticals, Tel Aviv, Israel) for 3 weeks. A controlled-release formulation was used to provide sufficient melatonin levels throughout the night; this formulation has been shown, in double-blind placebo-controlled studies, to be superior to placebo in improving sleep 26, 27. Each patient served as his or her own control for comparisons of the effects of melatonin versus placebo.

On each of the last three mornings of the placebo and treatment periods, patients reported their sleep the night before and their behavior in the morning using the Leeds Sleep Evaluation Questionnaire (42). This questionnaire includes 10 questions that measure four domains of sleep and morning behavior: ease of getting to sleep (mean of questions 1, 2, and 3); quality of sleep (mean of questions 4 and 5); hangover on awakening from sleep (mean of questions 6 and 7); and alertness and behavioral integrity the following morning (mean of questions 8, 9, and 10). Answers are provided on a 0- to 100-mm analog scale. The mean changes in the four domains at the end of the treatment period (as compared with the placebo period) were calculated for each patient. In accordance with other visual analog scale variables 43, 44, 45, clinical response was defined as a mean improvement of 10 mm or more.

Statistical analysis 

Normality of the distributions of 6-sulfatoxymelatonin values was examined with the Kolmogorov-Smirnov test. Because the nocturnal excretion of 6-sulfatoxymelatonin in patients with insomnia aged 55 years or older showed significant dispersions from normality, comparisons were performed using log-transformed values, with one-way analysis of variance and the Duncan post-hoc test. The normal range of 6-sulfatoxymelatonin was defined as the 2.5 to 97.5 percentiles for the log-transformed values in the healthy volunteers. Rates of response to melatonin treatment among patients by levels of 6-sulfatoxymelatonin excretion were analyzed with the chi-squared test for trend. Patients were also dichotomized into those excreting high and low 6-sulfatoxymelatonin levels; the rates of response to melatonin treatment between these two groups were compared using the chi-squared test. A P value <0.05 was considered significant. Statistical analyses were performed with SAS software, version 7 (SAS Institute Inc., Cary, North Carolina).

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Results 

Mean (± SD) nocturnal 6-sulfatoxymelatonin excretion was lower in the patients with insomnia (9 ± 8 μg per night) than in the older (18 ± 13 μg per night) or the younger healthy volunteers (24 ± 12 μg per night; Figure; P <0.001). Insomnia patients with chronic medical problems (specifically coronary heart disease) excreted significantly lower amounts of 6-sulfatoxymelatonin than those without these problems (Table 1).

  • View full-size image.
  • Figure. 

    Frequency distribution of nocturnal 6-sulfatoxymelatonin excretion in healthy volunteers (n = 30 [open squares], ages 20 to 35 years; n = 29 [open circles], ages ≥55 years) and in patients with insomnia aged ≥55 years (n = 517 [closed circles]).

Table 1. Nocturnal 6-Sulfatoxymelatonin Excretion in Insomnia Patients Aged ≤55 Years
Group of PatientsNo. of Patients6-Sulfatoxymelatonin Excretion (μg per night)P Value
Mean ± SD
Without chronic medical problems17210.4 ± 7.9
With chronic medical problems3458.3 ± 8.4<0.05*
Coronary heart disease596.5 ± 4.7<0.01*
Hypertension1628.2 ± 7.50.3*
Diabetes247.5 ± 6.00.4*
Country of origin
The Netherlands207.6 ± 4.6
Israel518.9 ± 7.5
France4468.9 ± 7.6

* Compared with patients who did not have chronic medical problems.

The normal range of 6-sulfatoxymelatonin excretion was defined as 8 to 56 μg per night for healthy adults aged 20 to 35 years and 4 to 55 μg per night for healthy adults aged 55 years or older. The median 6-sulfatoxymelatonin excretion in the patients with insomnia was 6.7 μg per night. More than half (56% [289/517]) of the insomnia patients excreted less 6-sulfatoxymelatonin than the amount considered to be normal for the healthy volunteers aged 20 to 35 years (≥8 μg per night), and 30% (155/517) excreted less than the amount considered to be normal for the older healthy adults (≥4 μg per night). Among the 172 insomnia patients without medical problems, 43% (n = 74) excreted less than 7 μg of 6-sulfatoxymelatonin per night and 16% (n = 28) excreted less than 3.5 mg of 6-sulfatoxymelatonin per night.

Response to melatonin treatment 

Of the 396 insomnia patients who were treated with placebo and melatonin (mean baseline excretion, 8.9 ± 7.8 μg per night), data on sleep quality were missing for one or both treatment periods in 24 patients. The remaining 372 were divided into six groups, based on their baseline 6-sulfatoxymelatonin excretion (Table 2). Lower baseline levels of excretion were associated with a significantly higher response to melatonin replacement therapy for three of the four outcome measures: ease of getting to sleep, quality of sleep, and alertness and behavioral integrity the following morning (Table 2).

Table 2. Relation between Nocturnal 6-Sulfatoxymelatonin Excretion and Subsequent Response to Melatonin Therapy
Category of Response*6-Sulfatoxymelatonin Excretion Range (μg per night)P for Trend†
0.15–0.62 (n = 10)0.63–1.25 (n = 14)1.26–2.5 (n = 46)2.6–5 (n = 71)5.1–10 (n = 107)10.1–80 (n = 124)
Number (%) Responders
Ease of getting to sleep8 (80)11 (79)22 (48)34 (48)41 (38)53 (43)0.005
Quality of sleep9 (90)8 (57)28 (61)33 (46)48 (45)62 (50)0.04
Hangover on awakening from sleep6 (60)4 (29)18 (39)22 (31)26 (24)42 (34)0.2
Alertness and behavioral integrity the following morning6 (60)5 (36)22 (48)2 (30)23 (21)35 (28)0.02

* Response was defined as a ≥10-mm improvement (on a 0- to 100-mm scale) compared with placebo.

† Chi-squared test for linear trend.

The percentage of responders to melatonin replacement therapy, as measured by improvement in quality of sleep, was significantly higher among the 112 low excretors of 6-sulfatoxymelatonin (≤3.5 μg per night) than among the remaining 260 patients (58% [n = 65] vs. 47% (n = 122), P <0.05). Similar results were seen for improvement in alertness and behavioral integrity (43% [n = 48] vs. 29% [n = 75], P <0.05), but not for ease of getting to sleep (51% [n = 57] vs. 42% [n = 109], P = 0.1) or hangover on awakening (36% [n = 40] vs. 30% [n = 78], P = 0.3).

Mean daytime 6-sulfatoxymelatonin excretion was 2.8 ± 4.4 μg/d (range, 0 to 67 μg/d) in the insomnia patients. The possibility that responders and nonresponders differed in the timing of melatonin excretion was examined by comparing the proportion of 6-sulfatoxymelatonin excreted during the night among responders and nonresponders (for quality of sleep). Mean nocturnal 6-sulfatoxymelatonin excretion was 73% ± 18% of the total amount excreted, and there was no difference between responders and nonresponders (P =0.4).

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Discussion 

Among patients with insomnia aged 55 years or older, low nocturnal melatonin production—as measured by urinary excretion of 6-sulfatoxymelatonin—is more common than among healthy persons of the same age who do not complain of sleep problems. Mean levels of excretion were especially low in patients with chronic medical problems, consistent with previous studies 24, 46, 47, 48. Insomnia patients who produce low amounts of melatonin are significantly more likely to benefit from melatonin replacement therapy than those who produce normal amounts.

Our results in healthy subjects aged 55 years or older without sleep problems (excretion of 4 to 55 μg of 6-sulfatoxymelatonin per night) are similar to previous reports 22, 23. Of note, low levels of excretion may be more common in the Southern hemisphere in patients aged 50 years or older (49).

Because melatonin replacement therapy was beneficial, particularly in patients with low melatonin production, we conclude that the decline in melatonin production with age (or perhaps with disease) impairs sleep in older patients. However, there is no systematic relation between melatonin production and objectively measured parameters of sleep, as measured in a sleep laboratory 30, 31, 32. This may not be surprising, as complaints in patients with insomnia do not correlate well with objective findings 7, 8. The partial overlap in 6-sulfatoxymelatonin excretion in patients with and without sleep complaints may explain the lack of a clear-cut correlation between 6-sulfatoxymelatonin excretion and subjective complaints of poor sleep 31, 32.

Melatonin might promote sleep via a circadian-entraining effect, rather than a sleep-regulating effect. For example, patients with an abnormal circadian phase should excrete less 6-sulfatoxymelatonin during the night and more during the daytime. We did not find a difference, however, between responders and nonresponders in the amount of 6-sulfatoxymelatonin excreted during the daytime; it therefore appears that an entraining effect of melatonin is not the major determinant of its efficacy. Rather, melatonin replacement therapy may improve sleep quality by treating an underlying deficiency in the endogenous production of this sleep-regulating hormone. It remains to be determined, however, whether the benefits of melatonin replacement therapy are sustained beyond the 3-week period that we studied.

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Acknowledgements 

We are thankful to Ricardo Tarrasch, MSc, Department of Psychology, Tel Aviv University, for thorough discussions and to Dr. Gilad Gal for the statistical analyses.

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☆ The study was supported by Neurim Pharmaceuticals, Tel Aviv, Israel.

PII: S0002-9343(03)00624-7

doi:10.1016/j.amjmed.2003.07.017

The American Journal of Medicine
Volume 116, Issue 2 , Pages 91-95, 15 January 2004

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