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

Manipulating the sleep-wake cycle and circadian rhythms to improve clinical management of major depression

BACKGROUND

Clinical psychiatry has always been limited by the lack of objective tests to substantiate diagnoses and a lack of specific treatments that target underlying pathophysiology. One area in which these twin failures has been most frustrating is major depression. Due to very considerable progress in the basic and clinical neurosciences of sleep-wake cycles and underlying circadian systems this situation is now rapidly changing.

DISCUSSION

The development of specific behavioral or pharmacological strategies that target these basic regulatory systems is driving renewed clinical interest. Here, we explore the extent to which objective tests of sleep-wake cycles and circadian function - namely, those that measure timing or synchrony of circadian-dependent physiology as well as daytime activity and nighttime sleep patterns - can be used to identify a sub-class of patients with major depression who have disturbed circadian profiles.

SUMMARY

Once this unique pathophysiology is characterized, a highly personalized treatment plan can be proposed and monitored. New treatments will now be designed and old treatments re-evaluated on the basis of their effects on objective measures of sleep-wake cycles, circadian rhythms and related metabolic systems.

Melatonin and mitochondrial dysfunction in the central nervous system

Cell death and survival are critical events for neurodegeneration, mitochondria being increasingly seen as important determinants of both. Mitochondrial dysfunction is considered a major causative factor in Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD). Increased free radical generation, enhanced mitochondrial inducible nitric oxide (NO) synthase activity and NO production, and disrupted electron transport system and mitochondrial permeability transition, have all been involved in impaired mitochondrial function. Melatonin, the major secretory product of the pineal gland, is an antioxidant and an effective protector of mitochondrial bioenergetic function. Both in vitro and in vivo, melatonin was effective to prevent oxidative stress/nitrosative stress-induced mitochondrial dysfunction seen in experimental models of AD, PD and HD. These effects are seen at doses 2-3 orders of magnitude higher than those required to affect sleep and circadian rhythms, both conspicuous targets of melatonin action. Melatonin is selectively taken up by mitochondria, a function not shared by other antioxidants. A limited number of clinical studies indicate that melatonin can improve sleep and circadian rhythm disruption in PD and AD patients. More recently, attention has been focused on the development of potent melatonin analogs with prolonged effects which were employed in clinical trials in sleep-disturbed or depressed patients in doses considerably higher than those employed for melatonin. In view that the relative potencies of the analogs are higher than that of the natural compound, clinical trials employing melatonin in the range of 50-100mg/day are needed to assess its therapeutic validity in neurodegenerative disorders.

Drugs for insomnia

INTRODUCTION

Sleep is a vital neurochemical process involving sleep-promoting and arousal centers in the brain. Insomnia is a pervasive disorder characterized by difficulties in initiating or maintaining or non-refreshing (poor quality) sleep and clinically significant daytime distress. Insomnia is more prevalent in women and old age and puts sufferers at significant physical and mental health risks. This review summarizes published data on the current and emerging insomnia drug classes, rationale for development and associated risks/benefits. (Summary of Product Characteristics and Medline search on "hypnotic" or specific drug names and "Insomnia").

AREAS COVERED

GABA(A) receptor modulators facilitate sleep onset and some improve maintenance but increase risk of dependence, memory, cognitive and psychomotor impairments, falls, accidents and mortality. Melatonin receptor agonists improve quality of sleep and/or sleep onset but response may develop over several days. They have more benign safety profiles and are indicated for milder insomnia, longer usage and (prolonged release melatonin) older patients. Histamine H-1 receptor antagonists improve sleep maintenance but their effects on cognition, memory and falls remain to be demonstrated. Late-stage pipeline orexin OX1/OX2 and serotonin 5HT2A receptor antagonists may hold the potential to address several unmet needs in insomnia pharmacotherapy but safety issues cast some doubts over their future.

EXPERT OPINION

Current and new insomnia drugs in the pipeline target different sleep regulating mechanisms and symptoms and have different tolerability profiles. Drug selection would ideally be based on improvement in the quality of patients' sleep, overall quality of life and functional status weighed against risk to the individual and public health.

Pharmacotherapy of insomnia

INTRODUCTION

Insomnia is one of the most prevalent sleep disorders in developed countries, being surpassed only by chronic sleep deprivation. Patients with insomnia tend to have an altered quality of life, impaired daytime functioning and an increased risk of work accidents and motor vehicle crashes. Insomnia is commonly associated with chronic medical conditions, metabolic illnesses and mental disorders (such as depression and anxiety), with which there is a dual, reciprocal relationship.

AREAS COVERED

This paper focuses on current pharmacotherapy options for the treatment of insomnia, particularly benzodiazepine receptor agonists, which nowadays represent the mainstay of hypnotic therapy. The melatonin receptor antagonist, ramelteon, is reviewed (an alternative for some patients with only sleep-onset difficulty), as are sedating antidepressants, which are commonly used 'off-label' to treat insomnia, despite limited efficacy data and potential significant safety concerns. Orexin (OX) antagonists are also discussed, especially those that block OX2 or both OX1 and OX2 receptors, as these are the most promising new agents for the treatment of insomnia, with encouraging results in preliminary clinical trials.

EXPERT OPINION

Research to evaluate and formulate treatments for insomnia is often complicated by the fact that insomnia is usually of multifactorial etiology. Understanding the molecular and receptor mechanisms involved in promoting sleep in varied disorders could provide future approaches in new drug development. In the long term, more randomized controlled trials are needed to assess both short-term and long-term effects of these medications and their efficacy in comorbid diseases that affect sleep quality or quantity.

Melatonin and its analogs in insomnia and depression

Benzodiazepine sedative-hypnotic drugs are widely used for the treatment of insomnia. Nevertheless, their adverse effects, such as next-day hangover, dependence and impairment of memory, make them unsuitable for long-term treatment. Melatonin has been used for improving sleep in patients with insomnia mainly because it does not cause hangover or show any addictive potential. However, there is a lack of consistency on its therapeutic value (partly because of its short half-life and the small quantities of melatonin employed). Thus, attention has been focused either on the development of more potent melatonin analogs with prolonged effects or on the design of slow release melatonin preparations. The MT(1) and MT(2) melatonergic receptor ramelteon was effective in increasing total sleep time and sleep efficiency, as well as in reducing sleep latency, in insomnia patients. The melatonergic antidepressant agomelatine, displaying potent MT(1) and MT(2) melatonergic agonism and relatively weak serotonin 5HT(2C) receptor antagonism, was found effective in the treatment of depressed patients. However, long-term safety studies are lacking for both melatonin agonists, particularly considering the pharmacological activity of their metabolites. In view of the higher binding affinities, longest half-life and relative higher potencies of the different melatonin agonists, studies using 2 or 3mg/day of melatonin are probably unsuitable to give appropriate comparison of the effects of the natural compound. Hence, clinical trials employing melatonin doses in the range of 50-100mg/day are warranted before the relative merits of the melatonin analogs versus melatonin can be settled.

Disaster hypertension - its characteristics, mechanism, and management -

The devastating Great East Japan Earthquake, which was 9.0 on the Richter scale, occurred on March 11, 2011. Japan experienced the Great Hanshin-Awaji Earthquake 16 years ago, and I was working at the epicenter, and reported the characteristics of the earthquake-associated cardiovascular risk and high blood pressure (BP) found during the continuous practice and clinical studies of Tsuna Medical Association before and after the quake. A major disaster increases thrombophilic tendency and BP, both of which trigger disaster-induced cardiovascular events such as stroke, cardiac events, etc. The high salt intake and the increased salt sensitivity caused by disrupted circadian rhythms are the 2 major leading causes of disaster hypertension (HT) through neurohumoral activation under stressful conditions. To better assess and reduce the risks for disaster-associated cardiovascular events, we introduced the web-based Disaster Cardiovascular Prevention (DCAP) network (which consists of DCAP risk and prevention score assessment, and self-measured BP monitoring at both the shelter and the home) to the survivors of the 2011 disaster, and frequently found newly developed HT. Here I review the recent evidence, possible mechanism and the management of "disaster HT" for effective prevention of disaster-induced cardiovascular events.

Efficacy and safety of prolonged-release melatonin for insomnia in middle-aged and elderly patients with hypertension: a combined analysis of controlled clinical trials

BACKGROUND

Add-on prolonged-release melatonin (PRM) in antihypertensive therapy has been shown to ameliorate nocturnal hypertension. Hypertension is a major comorbidity among insomnia patients. The efficacy and safety of PRM for primary insomnia in patients aged 55 years and older who are treated with antihypertensive drugs were evaluated.

METHODS

Post hoc analysis of pooled antihypertensive drug-treated subpopulations from four randomized, double-blind trials of PRM and placebo for 3 weeks (N[PRM] = 195; N[placebo] = 197) or 28 weeks (N[PRM] = 157; N[placebo] = 40). Efficacy measurements included Leeds Sleep Evaluation Questionnaire scores of quality of sleep and alertness and behavioral integrity the following morning after 3 weeks, and sleep latency (daily sleep diary) and Clinical Global Impression of Improvement (CGI-I) after 6 months of treatment. Safety measures included antihypertensive drug-treated subpopulations from these four and three additional single-blind and open-label PRM studies of up to 1 year (N[PRM] = 650; N[placebo] = 632).

RESULTS

Quality of sleep and behavior following wakening improved significantly with PRM compared with placebo (P < 0.0001 and P < 0.0008, respectively). Sleep latency (P = 0.02) and CGI-I (P = 0.0003) also improved significantly. No differences were observed between PRM and placebo groups in vital signs, including daytime blood pressure at baseline and treatment phases. The rate of adverse events normalized per 100 patient-weeks was lower for PRM (3.66) than for placebo (8.53).

CONCLUSIONS

The findings demonstrate substantive and sustained efficacy of PRM in primary insomnia patients treated with antihypertensive drugs. PRM appears to be safe for insomnia in patients with cardiovascular comorbidity.

Mood disorders, circadian rhythms, melatonin and melatonin agonists

Recent advances in the understanding of circadian rhythms have led to an interest in the treatment of major depressive disorder with chronobiotic agents. Many tissues have autonomous circadian rhythms, which are orchestrated by the master clock, situated in the suprachiasmatic nucleus (SNC). Melatonin (N-acetyl-5-hydroxytryptamine) is secreted from the pineal gland during darkness. Melatonin acts mainly on MT1 and MT2 receptors, which are present in the SNC, regulating physiological and neuroendocrine functions, including circadian entrainment, referred to as the chronobiotic effet. Circadian rhythms has been shown to be either misaligned or phase shifted or decreased in amplitude in both acute episodes and relapse of major depressive disorder (MDD) and bipolar disorder. Manipulation of circadian rhythms either using physical treatments (such as high intensity light) or behavioral therapy has shown promise in improving symptoms. Pharmacotherapy using melatonin and pure melatonin receptor agonists, while improving sleep, has not been shown to improve symptoms of depression. A novel antidepressant, agomelatine, combines 5HT2c antagonist and melatonin agonist action, and has shown promise in both acute treatment of MDD and in preventing relapse.

Genetic variations of the melatonin pathway in patients with attention-deficit and hyperactivity disorders

Melatonin is a powerful antioxidant and a synchronizer of many physiological processes. Alteration in melatonin signaling has been reported in a broad range of diseases, but little is known about the genetic variability of this pathway in humans. Here, we sequenced all the genes of the melatonin pathway -AA-NAT, ASMT, MTNR1A, MTNR1B and GPR50 - in 321 individuals from Sweden including 101 patients with attention-deficit/hyperactivity disorder (ADHD) and 220 controls from the general population. We could find several damaging mutations in patients with ADHD, but no significant enrichment compared with the general population. Among these variations, we found a splice site mutation in ASMT (IVS5+2T>C) and one stop mutation in MTNR1A (Y170X) - detected exclusively in patients with ADHD - for which biochemical analyses indicated that they abolish the activity of ASMT and MTNR1A. These genetic and functional results represent the first comprehensive ascertainment of melatonin signaling deficiency in ADHD.

Prolonged-release melatonin for insomnia - an open-label long-term study of efficacy, safety, and withdrawal

Background

Prolonged-release melatonin (PRM) 2 mg is indicated for insomnia in patients aged 55 years and older. A recent double-blind placebo-controlled study demonstrated 6-month efficacy and safety of PRM in insomnia patients aged 18–80 and lack of withdrawal and rebound symptoms upon discontinuation.

Objective

To investigate the efficacy, safety, and withdrawal phenomena associated with 6–12 months PRM treatment.

Methods

Data from a prospective 6–12-month open-label study of 244 community dwelling adults with primary insomnia, who had participated in a placebo-controlled, double-blind dose-ranging trial of PRM. Patients received PRM nightly, followed by a 2-week withdrawal period. Main outcome measures were patient-reported sleep quality ratings (diary), adverse events, vital signs, and laboratory tests recorded at each visit, and withdrawal symptoms (CHESS-84 [Check-list Evaluation of Somatic Symptoms]). Nocturnal urinary 6-sulfatoxymelatonin excretion, a measure of the endogenous melatonin production, was assessed upon discontinuing long-term PRM.

Results

Of the 244 patients, 36 dropped out, 112 completed 6 months of treatment, and the other 96 completed 12 months of treatment. The mean number of nights by which patients reported sleep quality as “good” or “very good” was significantly higher during PRM than before treatment. There was no evidence of tolerance to PRM. Discontinuation of PRM was not associated with rebound insomnia or withdrawal symptoms; on the contrary, residual benefit was observed. PRM was well tolerated, and there was no suppression of endogenous melatonin production.

Conclusion

Results support the efficacy and safety of PRM in primary insomnia patients aged 20–80 throughout 6–12 months of continuous therapy. PRM discontinuation even after 12 months was not associated with adverse events, withdrawal symptoms, or suppression of endogenous melatonin production.

Melatonin decreases delirium in elderly patients: a randomized, placebo-controlled trial

BACKGROUND

Disturbance in the metabolism of tryptophan and tryptophan-derived compounds (e.g., melatonin) may have a role in the pathogenesis of delirium.

OBJECTIVE

To evaluate the efficacy of low dose exogenous melatonin in decreasing delirium.

DESIGN

A randomized, double-blinded, placebo-controlled study.

SETTING

An Internal Medicine service in a tertiary care centre in London, Ontario, Canada.

PARTICIPANTS

145 individuals aged 65 years or over admitted through the emergency department to a medical unit in a tertiary care hospital.

INTERVENTION

Patients were randomized to receive either 0.5 mg of melatonin or placebo every night for 14 days or until discharge.

MEASUREMENTS

The primary outcome was the occurrence of delirium as determined by Confusion Assessment Method (CAM) criteria.

RESULTS

Of a total of 145 individuals (mean age (standard deviation): 84.5 (6.1) years) 72 were randomly assigned to the melatonin group and 73 to the placebo group. Melatonin was associated with a lower risk of delirium (12.0% vs. 31.0%, p = 0.014), with an odds ratio (OR), adjusted for dementia and co-morbidities of 0.19 (95% confidence intervals (CI): 0.06-0.62). Results were not different when patients with prevalent delirium were excluded.

LIMITATION

An intention to treat analysis was not possible due to loss to follow-up.

CONCLUSION

Exogenous low dose melatonin administered nightly to elderly patients admitted to acute care may represent a potential protective agent against delirium.

Melatonin agonists in primary insomnia and depression-associated insomnia: are they superior to sedative-hypnotics?

Current pharmacological treatment of insomnia involves the use of sedative-hypnotic benzodiazepine and non-benzodiazepine drugs. Although benzodiazepines improve sleep, their multiple adverse effects hamper their application. Adverse effects include impairment of memory and cognitive functions, next-day hangover and dependence. Non-benzodiazepines are effective for initiating sleep but are not as effective as benzodiazepines for improving sleep quality or efficiency. Furthermore, their prolonged use produces adverse effects similar to those observed with benzodiazepines. Inasmuch as insomnia may be associated with decreased nocturnal melatonin, administration of melatonin is a strategy that has been increasingly used for treating insomnia. Melatonin can be effective for improving sleep quality without the adverse effects associated with hypnotic-sedatives. Ramelteon, a synthetic analog of melatonin which has a longer half life and a stronger affinity for MT1 and MT2 melatonergic receptors, has been reportedly effective for initiating and improving sleep in both adult and elderly insomniacs without showing hangover, dependence, or cognitive impairment. Insomnia is also a major complaint among patients suffering from depressive disorders and is often aggravated by conventional antidepressants especially the specific serotonin reuptake inhibitors. The novel antidepressant agomelatine, a dual action agent with affinity for melatonin MT1 and MT2 receptors and 5-HT2c antagonistic properties, constitutes a new approach to the treatment of major depressive disorders. Agomelatine ameliorates the symptoms of depression and improves the quality and efficiency of sleep. Taken together, the evidence indicates that MT1/MT2 receptor agonists like ramelteon or agomelatine may be valuable pharmacological tools for insomnia and for depression-associated insomnia.

Cherries and health: a review

Cherries, and in particular sweet cherries, are a nutritionally dense food rich in anthocyanins, quercetin, hydroxycinnamates, potassium, fiber, vitamin C, carotenoids, and melatonin. UV concentration, degree of ripeness, postharvest storage conditions, and processing, each can significantly alter the amounts of nutrients and bioactive components. These constituent nutrients and bioactive food components support the potential preventive health benefits of cherry intake in relation to cancer, cardiovascular disease, diabetes, inflammatory diseases, and Alzheimer's disease. Mechanistically, cherries exhibit relatively high antioxidant activity, low glycemic response, COX 1 and 2 enzyme inhibition, and other anti-carcinogenic effects in vitro and in animal experiments. Well-designed cherry feeding studies are needed to further substantiate any health benefits in humans.

Prolonged release melatonin in the treatment of primary insomnia: evaluation of the age cut-off for short- and long-term response

OBJECTIVES

The authors recently reported on efficacy and safety of prolonged-release melatonin formulation (PRM; Circadin 2  mg) in elderly insomnia patients. The age cut-off for response to PRM and the long-term maintenance of efficacy and safety were further evaluated by looking at the total cohort (age 18-80 years) from that study and subsets of patients aged 18-54 and 55-80 years (for whom the drug is currently indicated).

DESIGN

Randomised, double-blind, placebo controlled trial.

SETTING

Multicentre, outpatients, primary care setting.

METHODS

A total of 930 males and females aged 18-80 years with primary insomnia who reported mean nightly sleep latency (SL) >20  min were enrolled and 791 entered the active phase of the study. The study comprised a 2-week, single-blind placebo run-in period followed by 3 week's double-blind treatment with PRM or placebo, one tablet per day at 2 hours before bedtime. PRM patients continued whereas placebo completers were re-randomised 1:1 to PRM or placebo for 26 weeks followed by 2-weeks run-out on placebo.

MAIN OUTCOME MEASURES

SL and other sleep variables derived from sleep diary, Pittsburgh Sleep Quality Index (PSQI), Quality of life (WHO-5), Clinical Global Impression of Improvement (CGI-I) and adverse effects, recorded each visit, withdrawal and rebound effects during run-out.

RESULTS

In all, 746 patients completed the 3-week and 555 (421 PRM, 134 placebo) completed the 6-month period. The principal reason for drop-out was patient decision. At 3 weeks, significant differences in SL (diary, primary variable) in favour of PRM vs. placebo treatment were found for the 55-80-year group (-15.4 vs. -5.5  min, p = 0.014) but not the 18-80-year cut-off which included younger patients. Other variables (SL-PSQI, PSQI, WHO-5, CGI-I scores) improved significantly with PRM in the 18-80-year population, more so than in the 55-80-year age group. Improvements were maintained or enhanced over the 6-month period with no signs of tolerance. No withdrawal symptoms or rebound insomnia were detected. Most adverse events were mild with no significant differences between PRM and placebo groups in any safety outcome.

CONCLUSIONS

The results demonstrate short- and long-term efficacy of PRM in insomnia patients aged 18-80 years, particularly those aged 55 and over. PRM was well-tolerated over the entire 6-month period with no rebound or withdrawal symptoms following discontinuation. Study Registry No: ClinicalTrials.gov ID: NCT00397189.

Efficacy and safety of prolonged-release melatonin in insomnia patients with diabetes: a randomized, double-blind, crossover study

BACKGROUND

Diabetes is a major comorbidity in insomnia patients. The efficacy and safety of prolonged-release melatonin 2 mg in the treatment of glucose, lipid metabolism, and sleep was studied in 36 type 2 diabetic patients with insomnia (11 men, 25 women, age 46-77 years).

METHODS

In a randomized, double-blind, crossover study, the subjects were treated for 3 weeks (period 1) with prolonged-release melatonin or placebo, followed by a one-week washout period, and then crossed over for another 3 weeks (period 2) of treatment with the other preparation. All tablets were taken 2 hours before bedtime for a period of 3 weeks. In an extension period of 5 months, prolonged-release melatonin was given nightly to all patients in an open-label design. Sleep was objectively monitored in a subgroup of 22 patients using wrist actigraphy. Fasting glucose, fructosamine, insulin, C-peptide, triglycerides, total cholesterol, high-density and low-density lipoprotein cholesterol, and some antioxidants, as well as glycosylated hemoglobin (HbA1c) levels were measured at baseline and at the end of the study. All concomitant medications were continued throughout the study.

RESULTS

No significant changes in serum glucose, fructosamine, insulin, C-peptide, antioxidant levels or blood chemistry were observed after 3 weeks of prolonged-release melatonin treatment. Sleep efficiency, wake time after sleep onset, and number of awakenings improved significantly with prolonged-release melatonin as compared with placebo. Following 5 months of prolonged-release melatonin treatment, mean HbA1c (±standard deviation) was significantly lower than at baseline (9.13% ± 1.55% versus 8.47% ± 1.67%, respectively, P = 0.005).

CONCLUSION

Short-term use of prolonged-release melatonin improves sleep maintenance in type 2 diabetic patients with insomnia without affecting glucose and lipid metabolism. Long-term prolonged-release melatonin administration has a beneficial effect on HbA1c, suggesting improved glycemic control.

British Association for Psychopharmacology consensus statement on evidence-based treatment of insomnia, parasomnias and circadian rhythm disorders

Sleep disorders are common in the general population and even more so in clinical practice, yet are relatively poorly understood by doctors and other health care practitioners. These British Association for Psychopharmacology guidelines are designed to address this problem by providing an accessible up-to-date and evidence-based outline of the major issues, especially those relating to reliable diagnosis and appropriate treatment. A consensus meeting was held in London in May 2009. Those invited to attend included BAP members, representative clinicians with a strong interest in sleep disorders and recognized experts and advocates in the field, including a representative from mainland Europe and the USA. Presenters were asked to provide a review of the literature and identification of the standard of evidence in their area, with an emphasis on meta-analyses, systematic reviews and randomized controlled trials where available, plus updates on current clinical practice. Each presentation was followed by discussion, aimed to reach consensus where the evidence and/or clinical experience was considered adequate or otherwise to flag the area as a direction for future research. A draft of the proceedings was then circulated to all participants for comment. Key subsequent publications were added by the writer and speakers at draft stage. All comments were incorporated as far as possible in the final document, which represents the views of all participants although the authors take final responsibility for the document.

International Union of Basic and Clinical Pharmacology. LXXV. Nomenclature, classification, and pharmacology of G protein-coupled melatonin receptors

The hormone melatonin (5-methoxy-N-acetyltryptamine) is synthesized primarily in the pineal gland and retina, and in several peripheral tissues and organs. In the circulation, the concentration of melatonin follows a circadian rhythm, with high levels at night providing timing cues to target tissues endowed with melatonin receptors. Melatonin receptors receive and translate melatonin's message to influence daily and seasonal rhythms of physiology and behavior. The melatonin message is translated through activation of two G protein-coupled receptors, MT(1) and MT(2), that are potential therapeutic targets in disorders ranging from insomnia and circadian sleep disorders to depression, cardiovascular diseases, and cancer. This review summarizes the steps taken since melatonin's discovery by Aaron Lerner in 1958 to functionally characterize, clone, and localize receptors in mammalian tissues. The pharmacological and molecular properties of the receptors are described as well as current efforts to discover and develop ligands for treatment of a number of illnesses, including sleep disorders, depression, and cancer.

Nightly treatment of primary insomnia with prolonged release melatonin for 6 months: a randomized placebo controlled trial on age and endogenous melatonin as predictors of efficacy and safety

BACKGROUND

Melatonin is extensively used in the USA in a non-regulated manner for sleep disorders. Prolonged release melatonin (PRM) is licensed in Europe and other countries for the short term treatment of primary insomnia in patients aged 55 years and over. However, a clear definition of the target patient population and well-controlled studies of long-term efficacy and safety are lacking. It is known that melatonin production declines with age. Some young insomnia patients also may have low melatonin levels. The study investigated whether older age or low melatonin excretion is a better predictor of response to PRM, whether the efficacy observed in short-term studies is sustained during continued treatment and the long term safety of such treatment.

METHODS

Adult outpatients (791, aged 18-80 years) with primary insomnia, were treated with placebo (2 weeks) and then randomized, double-blind to 3 weeks with PRM or placebo nightly. PRM patients continued whereas placebo completers were re-randomized 1:1 to PRM or placebo for 26 weeks with 2 weeks of single-blind placebo run-out. Main outcome measures were sleep latency derived from a sleep diary, Pittsburgh Sleep Quality Index (PSQI), Quality of Life (World Health Organzaton-5) Clinical Global Impression of Improvement (CGI-I) and adverse effects and vital signs recorded at each visit.

RESULTS

On the primary efficacy variable, sleep latency, the effects of PRM (3 weeks) in patients with low endogenous melatonin (6-sulphatoxymelatonin [6-SMT] <or=8 microg/night) regardless of age did not differ from the placebo, whereas PRM significantly reduced sleep latency compared to the placebo in elderly patients regardless of melatonin levels (-19.1 versus -1.7 min; P = 0.002). The effects on sleep latency and additional sleep and daytime parameters that improved with PRM were maintained or enhanced over the 6-month period with no signs of tolerance. Most adverse events were mild in severity with no clinically relevant differences between PRM and placebo for any safety outcome.

CONCLUSIONS

The results demonstrate short- and long-term efficacy and safety of PRM in elderly insomnia patients. Low melatonin production regardless of age is not useful in predicting responses to melatonin therapy in insomnia. The age cut-off for response warrants further investigation.

MT2 melatonin receptor immunoreactivity in neurons is very high in the aged hippocampal formation in gerbils

Melatonin exerts many physiological functions via its G protein-coupled receptors. In the present study, we investigated age-related changes in MT2 melatonin receptor immunoreactivity and its levels in the gerbil hippocampus during normal aging. In the postnatal month 1 (PM 1) group, MT2 immunoreaction was well observed in neurons in all subregions of the gerbil hippocampus. In the PM 3 and 6 groups, MT2 immunoreactivity in neurons was decreased compared to that in the PM 1 group. Thereafter, MT2 immunoreactivity in neurons was increased. In the PM 18 and 24 groups, MT2 immunoreactivity in neurons was strong in all subregions of the gerbil hippocampus. In addition, the number of MT2 immunoreactive cells was lowest at PM 3 and highest at PM 24. From western blot analysis, age-dependent change pattern in MT2 level in the gerbil hippocampus was similar to the immunohistochemical result. These results indicate that MT2 immunoreactivity and levels are altered in the gerbil hippocampus during normal aging; lowest at young adult stage and highest at aged stage.

The effect of prolonged-release melatonin on sleep measures and psychomotor performance in elderly patients with insomnia

Objectives of this study were to investigate the effects of prolonged-release melatonin 2 mg (PRM) on sleep and subsequent daytime psychomotor performance in patients aged > or =55 years with primary insomnia, as defined by fourth revision of the Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Association. Patients (N = 40) were treated nightly single-blind with placebo (2 weeks), randomized double-blind to PRM or placebo (3 weeks) followed by withdrawal period (3 weeks). Sleep was assessed by polysomnography, all-night sleep electroencephalography spectral analysis and questionnaires. Psychomotor performance was assessed by the Leeds Psychomotor Test battery. By the end of the double-blind treatment, the PRM group had significantly shorter sleep onset latency (9 min; P = 0.02) compared with the placebo group and scored significantly better in the Critical Flicker Fusion Test (P = 0.008) without negatively affecting sleep structure and architecture. Half of the patients reported substantial improvement in sleep quality at home with PRM compared with 15% with placebo (P = 0.018). No rebound effects were observed during withdrawal. In conclusion, nightly treatment with PRM effectively induced sleep and improved perceived quality of sleep in patients with primary insomnia aged > or =55 years. Daytime psychomotor performance was not impaired and was consistently better with PRM compared with placebo. PRM was well tolerated with no evidence of rebound effects.

Urinary 6‐hydroxymelatonin sulfate excretion in intellectually disabled subjects with sleep disorders and multiple medications: Validation of measurements in urine extracted from diapers

The aim of this study was to examine the applicability of urinary 6-hydroxymelatonin sulfate (MT6s) measurements in the evaluation of melatonin secretion in intellectually disabled patients with sleep disorders. All 17 patients received drugs with potential interactions with melatonin metabolism. Serum melatonin 24-h profiles were determined at hourly intervals. The area under the curve (AUC) value, peak amplitude, half-rise time, and half-decline time were calculated individually. Urinary MT6s excretion was determined from samples collected from disposable diapers during three consecutive days at varying intervals. The average excretion rate for each hour of the day was calculated. The excretion profiles were characterized by total amount of MT6s excretion/24 h/kg body mass, amount of excreted MT6s during 6 h of maximum excretion (MAX 6h), and start time of the maximum excretion (start MAX 6h). There were significant positive correlations between serum melatonin AUC value and total excretion of MT6s/body mass, between serum melatonin amplitude and urinary MAX 6h, and between melatonin half-rise time and start MAX 6h; one patient on phenobarbital medication was out of line. The serum melatonin profiles of the patients were classified by comparing them with those of matched healthy volunteers (low-, normal-, or high secretors, normal or delayed rhythm). Similarly, the parameters of MT6s profiles were compared with those obtained from healthy controls, and the patients were reclassified as normal or aberrant. The classifications based on serum melatonin and urinary MT6s measurements were mostly concordant. The daily pattern of urinary MT6s excretion reliably reflected the phase of the serum melatonin rhythm irrespective of the medications, but in some cases, the total amount of excreted MT6s was lower than expected based on serum melatonin measurements.

Ramelteon: a review of its therapeutic potential in sleep disorders

Ramelteon is a tricyclic synthetic analog of melatonin that acts specifically on MT(1) and MT(2) melatonin receptors. Ramelteon's half-life is longer than that of melatonin, being metabolized in the body to four main metabolites, M-I, M-II, M-III, and M-IV. M-II has an affinity to MT(1) and MT(2) of about one-tenth of the parent compound, but its concentration in the circulation exceeds that of ramelteon by more than an order of magnitude. Ramelteon is effective in decreasing latency to persistent sleep and increasing total sleep time in freely moving monkeys. A number of clinical studies have been undertaken to study the efficacy of ramelteon in subjects with chronic insomnia. In almost all of these studies, ramelteon, in various doses of 4, 8, or 16 mg most commonly, significantly reduced sleep latency and increased sleep duration. Its primary action in sleep promotion is not a generalized gamma-aminobutyric (GABA)-ergic central nervous system depression, but rather it acts as a melatonergic agonist in the suprachiasmatic nucleus (and at other central nervous system sites), from where downstream processes, including GABA-ergic effects, are controlled via the hypothalamic sleep switch. Unlike other commonly prescribed hypnotic drugs, ramelteon is not associated with next morning hangover effects or reductions in alertness, nor has it been shown to cause withdrawal symptoms. The adverse symptoms reported with ramelteon are mild. All long-term investigations that have been carried out support the conclusion that ramelteon is a well tolerated and effective drug for the treatment of insomnia.

Melatonin and melatonergic drugs on sleep: possible mechanisms of action

Pineal melatonin is synthesized and secreted in close association with the light/dark cycle. The temporal relationship between the nocturnal rise in melatonin secretion and the "opening of the sleep gate" (i.e., the increase in sleep propensity at the beginning of the night), coupled with the sleep-promoting effects of exogenous melatonin, suggest that melatonin is involved in the regulation of sleep. The sleep-promoting and sleep/wake rhythm regulating effects of melatonin are attributed to its action on MT(1) and MT(2) melatonin receptors present in the suprachiasmatic nucleus (SCN) of the hypothalamus. Animal experiments carried out in rats, cats, and monkeys have revealed that melatonin has the ability to reduce sleep onset time and increase sleep duration. However, clinical studies reveal inconsistent findings, with some of them reporting beneficial effects of melatonin on sleep, whereas in others only marginal effects are documented. Recently a prolonged-release 2-mg melatonin preparation (Circadin(TM)) was approved by the European Medicines Agency as a monotherapy for the short-term treatment of primary insomnia in patients who are aged 55 or above. Several melatonin derivatives have been shown to increase nonrapid eye movement (NREM) in rats and are of potential pharmacological importance. So far only one of these melatonin derivatives, ramelteon, has received approval from the U.S. Food and Drug Administration to be used as a sleep promoter. Ramelteon is a novel MT(1) and MT(2) melatonergic agonist that has specific effects on melatonin receptors in the SCN and is effective in promoting sleep in experimental animals such as cats and monkeys. In clinical trials, ramelteon reduced sleep onset latency and promoted sleep in patients with chronic insomnia, including an older adult population. Both melatonin and ramelteon promote sleep by regulating the sleep/wake rhythm through their actions on melatonin receptors in the SCN, a unique mechanism of action not shared by any other hypnotics. Moreover, unlike benzodiazepines, ramelteon causes neither withdrawal effects nor dependence. Agomelatine, another novel melatonergic antidepressant in its final phase of approval for clinical use, has been shown to improve sleep in depressed patients and to have an antidepressant efficacy that is partially attributed to its effects on sleep-regulating mechanisms.

Late evening brain activation patterns and their relation to the internal biological time, melatonin, and homeostatic sleep debt

Sleep propensity increases sharply at night. Some evidence implicates the pineal hormone melatonin in this process. Using functional magnetic resonance imaging, brain activation during a visual search task was examined at 22:00 h (when endogenous melatonin levels normally increase). The relationships between brain activation, endogenous melatonin (measured in saliva), and self-reported fatigue were assessed. Finally, the effects of exogenous melatonin administered at 22:00 h were studied in a double blind, placebo-controlled crossover manner. We show that brain activation patterns as well as the response to exogenous melatonin significantly differ at night from those seen in afternoon hours. Thus, activation in the rostro-medial and lateral aspects of the occipital cortex and the thalamus diminished at 22:00 h. Activation in the right parietal cortex increased at night and correlated with individual fatigue levels, whereas exogenous melatonin given at 22:00 h reduced activation in this area. The right dorsolateral prefrontal cortex, an area considered to reflect homeostatic sleep debt, demonstrated increased activation at 22:00 h. Surprisingly, this increase correlated with endogenous melatonin. These results demonstrate and partially differentiate circadian effects (whether mediated by melatonin or not) and homeostatic sleep debt modulation of human brain activity associated with everyday fatigue at night.

Effect of melatonin administration on sleep, behavioral disorders and hypnotic drug discontinuation in the elderly: a randomized, double-blind, placebo-controlled study

BACKGROUND AND AIMS

The aim of the study was to evaluate the effect of melatonin administration on sleep and behavioral disorders in the elderly and the facilitation of the discontinuation of regular hypnotic drugs.

METHODS

This was a prospective, randomized, double-blind, placebo-controlled, crossover trial in a community-living population. Participants were 22 older adults (7 men, 15 women over 65) with a history of sleep disorder complaints. Fourteen of these subjects were receiving hypnotic drug therapy. Participants received 2 months of melatonin (5 mg/day) and 2 months of placebo. Sleep disorders were evaluated with the Northside Hospital Sleep Medicine Institute (NHSMI) test, discarding secondary insomnia and evaluating sleep quality. Behavioral disorders were evaluated with the Yesavage Geriatric Depression Scale (GDS) and Goldberg Anxiety Scale (GAS). Patients discontinuing hypnotic drugs were also recorded.

RESULTS

Melatonin treatment for two months significantly improved sleep quality scores measured by the NHSMI test (1.78+/-0.40) when compared with both basal (3.72+/-0.45; p=0.001) and placebo (3.44+/-0.56; p=0.025) groups. Depression measured by GDS and anxiety measured by GAS also improved significantly after melatonin administration (p=0.043 and p=0.009, respectively). Nine out of 14 subjects receiving hypnotic drugs were able to discontinue this treatment during melatonin but not placebo administration; one discontinued hypnotic drugs during both melatonin and placebo administration, and four were unable to discontinue hypnotic therapy.

CONCLUSIONS

The results of this study suggest that melatonin administration significantly improves sleep and behavioral disorders in the elderly and facilitates discontinuation of therapy with conventional hypnotic drugs.

Prolonged-release melatonin for the treatment of insomnia in patients over 55 years

BACKGROUND

Clinical data show that poor quality, rather than quantity, of sleep corresponds negatively to measures of health, well-being and satisfaction with life. However, until now treatment of insomnia has primarily targeted quantity of sleep. PR (prolonged release)-melatonin offers a new treatment option in insomnia.

OBJECTIVES

To provide an overview of PR-melatonin, the first melatonin receptor agonist to be granted marketing authorisation in Europe as monotherapy for the treatment of primary insomnia in patients aged > 55 years.

METHODS

Review data published in peer review journals and the EMEA (European Medicines Agency) website.

RESULTS/CONCLUSION

PR-melatonin significantly improves morning alertness and quality of sleep compared with placebo. There are no safety concerns.

Effects of prolonged-release melatonin, zolpidem, and their combination on psychomotor functions, memory recall, and driving skills in healthy middle aged and elderly volunteers

BACKGROUND

Melatonin is an important regulator of the sleep-wake cycle. A prolonged-release formulation of melatonin (PR-M) that essentially mimics the profile of the endogenous production of the hormone is effective in the treatment of insomnia in patients aged 55 years and older. Because hypnotics result in impairments of various cognitive skills, it is important to examine the cognitive effects associated with the use of PR-M.

OBJECTIVES AND METHODS

The effects of therapeutic oral doses of PR-M (2 mg), zolpidem (10 mg) and their combination administered at bedtime on cognitive functions in healthy subjects aged 55 years and older (12 males + 4 females, age 59.4 +/- 3.2 years) were assessed in a randomized, double-blind, placebo-controlled, and four-way crossover study. Psychomotor functions, memory recall, and driving skills were assessed at 1 and 4 h following administration and the next morning.

RESULTS

Compared to placebo, PR-M alone did not impaired performances on any cognitive tasks. Zolpidem significantly impaired psychomotor and driving performance 1 h and 4 h post-dosing, and early memory recall; these impairment were exacerbated with PR-M co-administration. No effects on next morning psychomotor or driving performance were observed except that the decline in memory recall after zolpidem was more pronounced in the next day. No pharmacokinetic interactions were found.

CONCLUSIONS

This study extends previous researches showing impairment of cognitive functions by zolpidem within 5 h post-administration. Further, PR-M use was not found associated with impairment of psychomotor functions, memory recall, and driving skills, and point to a pharmacodynamic interaction between melatonin and GABA-A modulators.

The roles of melatonin and light in the pathophysiology and treatment of circadian rhythm sleep disorders

Normal circadian rhythms are synchronized to a regular 24 h environmental light-dark cycle, and the suprachiasmatic nucleus and the hormone melatonin have important roles in this process. Desynchronization of circadian rhythms, as occurs in chronobiological disorders, can produce severe disturbances in sleep patterns. According to the International Classification of Sleep Disorders, circadian rhythm sleep disorders (CRSDs) include delayed sleep phase syndrome, advanced sleep phase syndrome, non-24 h sleep-wake disorder, jet lag and shift-work sleep disorder. Disturbances in the circadian phase position of plasma melatonin levels have been documented in all of these disorders. There is compelling evidence to implicate endogenous melatonin as an important mediator in CRSD pathophysiology, although further research involving large numbers of patients will be required to clarify whether the disruption of melatonin secretion is a causal factor in CRSDs. In this Review, we focus on the use of exogenous melatonin and light therapy to treat the disturbed sleep-wake rhythms seen in CRSDs.

Role of the melatonin system in the control of sleep: therapeutic implications

The circadian rhythm of pineal melatonin secretion, which is controlled by the suprachiasmatic nucleus (SCN), is reflective of mechanisms that are involved in the control of the sleep/wake cycle. Melatonin can influence sleep-promoting and sleep/wake rhythm-regulating actions through the specific activation of MT(1) (melatonin 1a) and MT(2) (melatonin 1b) receptors, the two major melatonin receptor subtypes found in mammals. Both receptors are highly concentrated in the SCN. In diurnal animals, exogenous melatonin induces sleep over a wide range of doses. In healthy humans, melatonin also induces sleep, although its maximum hypnotic effectiveness, as shown by studies of the timing of dose administration, is influenced by the circadian phase. In both young and elderly individuals with primary insomnia, nocturnal plasma melatonin levels tend to be lower than those in healthy controls. There are data indicating that, in affected individuals, melatonin therapy may be beneficial for ameliorating insomnia symptoms. Melatonin has been successfully used to treat insomnia in children with attention-deficit hyperactivity disorder or autism, as well as in other neurodevelopmental disorders in which sleep disturbance is commonly reported. In circadian rhythm sleep disorders, such as delayed sleep-phase syndrome, melatonin can significantly advance the phase of the sleep/wake rhythm. Similarly, among shift workers or individuals experiencing jet lag, melatonin is beneficial for promoting adjustment to work schedules and improving sleep quality. The hypnotic and rhythm-regulating properties of melatonin and its agonists (ramelteon, agomelatine) make them an important addition to the armamentarium of drugs for treating primary and secondary insomnia and circadian rhythm sleep disorders.

Prolonged-release melatonin improves sleep quality and morning alertness in insomnia patients aged 55 years and older and has no withdrawal effects

Melatonin, secreted nocturnally by the pineal gland, is an endogenous sleep regulator. Impaired melatonin production and complaints on poor quality of sleep are common among the elderly. Non-restorative sleep (perceived poor quality of sleep) and subsequently poor daytime functioning are increasingly recognized as a leading syndrome in the diagnostic and therapeutic process of insomnia complaints. The effects of 3-weeks prolonged-release melatonin 2 mg (PR-melatonin) versus placebo treatment were assessed in a multi-center randomized placebo-controlled study in 170 primary insomnia outpatients aged > or =55 years. Improvements in quality of sleep (QOS) the night before and morning alertness (BFW) were assessed using the Leeds Sleep Evaluation Questionnaire and changes in sleep quality (QON) reported on five categorical unit scales. Rebound insomnia and withdrawal effects following discontinuation were also evaluated. PR-melatonin significantly improved QOS (-22.5 versus -16.5 mm, P = 0.047), QON (0.89 versus 0.46 units; P = 0.003) and BFW (-15.7 versus -6.8 mm; P = 0.002) compared with placebo. The improvements in QOS and BFW were strongly correlated (Rval = 0.77, P < 0.001) suggesting a beneficial treatment effect on the restorative value of sleep. These results were confirmed in a subgroup of patients with a greater symptom severity. There was no evidence of rebound insomnia or withdrawal effects following treatment discontinuation. The incidence of adverse events was low and most side-effects were judged to be of minor severity. PR-melatonin is the first drug shown to significantly improve quality of sleep and morning alertness in primary insomnia patients aged 55 years and older-suggesting more restorative sleep, and without withdrawal symptoms upon discontinuation.

Pharmacotherapy of insomnia

Insomnia is the most common sleep disorder in the industrialized world. A variety of precipitating events have been identified, but when it becomes a persistent problem, maladaptive patterns become established, thereby, perpetuating the sleep disturbance. Individuals with insomnia have impaired next-day functioning, which impacts their quality of life and places them at increased risk of motor vehicle accidents. Insomnia is commonly associated with chronic medical conditions, as well as an increased incidence of mental disorders. Despite considerable scientific advances in both the understanding and treatment, insomnia continues to be inadequately identified and treated, with < 15% of those with severe insomnia receiving appropriate treatment. The mainstay of treatment for insomnia is cognitive-behavioral therapy, along with judicious use of hypnotic agents.

Complementary and alternative medicine for sleep disturbances in older adults

Complementary and alternative medicines (CAM) are frequently used for the treatment of sleep disorders, but in many cases patients do not discuss these therapies directly with their health care provider. There is a growing body of well-designed clinical trials using CAM that have shown the following: (1) Melatonin is an effective agent for the treatment of circadian phase disorders that affect sleep; however, the role of melatonin in the treatment of primary or secondary insomnia is less well established. (2) Valerian has shown a benefit in some, but not all clinical trials. (3) Several other modalities, such as Tai Chi, acupuncture, acupressure, yoga, and meditation have improved sleep parameters in a limited number of early trials. Future work examining CAM has the potential to significantly add to our treatment options for sleep disorders in older adults.

Prolonged-release melatonin for the treatment of insomnia: targeting quality of sleep and morning alertness

Prolonged-release (PR) melatonin (Circadin®, Neurim Pharmaceuticals, Tel-Aviv, Israel) is a nonbenzodiazepine licensed to treat primary insomnia in patients aged 55 years and older. It exerts its effects by mimicking endogenous melatonin, a hormone which regulates sleep. PR-melatonin has been shown to be effective in improving quality of sleep and morning alertness. An oral dose of 2 mg once-daily for 3 weeks has generally been well tolerated, and does not cause ‘hangover’ effects or impair memory and psychomotor skills.

Drug Insight: the use of melatonergic agonists for the treatment of insomnia-focus on ramelteon

Melatonin, a chronobiotic that participates in the control of the circadian system, is known for its sleep-promoting effects, which include shortening of sleep latency and lengthening of sleep duration. As a result of its short half-life, melatonin does not exhibit undesirable side effects, and its broad applicability for a variety of sleep problems has been the focus of numerous scientific studies. Melatonin has not, however, received regulatory approval from the US FDA as a drug, because it can be sold freely as a food supplement. Consequently, there has been an active search for patentable melatonin receptor ligands in recent years. Ramelteon, an agonist that acts solely on melatonin MT(1) and MT(2) receptors, is of particular interest, and preliminary research indicates that it holds considerable promise for clinical applications. Ramelteon has been shown to induce sleep initiation and maintenance in various animal models and in clinical trials. In chronic insomnia, ramelteon decreases sleep latency and increases total sleep time and sleep efficiency, without causing hangover, addiction or withdrawal effects. Ramelteon is thought to promote sleep by influencing homeostatic sleep signaling mediated by the suprachiasmatic nucleus. Although ramelteon's metabolism and pharmacokinetics differ from those of melatonin, its safety seems to be sufficient for short-term application. Its long-term effects remain to be determined.

Endogenous melatonin predicts efficacy of exogenous melatonin in consolidation of fragmented wrist-activity rhythm of adult patients with developmental brain disorders: A double-blind, placebo-controlled, crossover study

OBJECTIVE

: We studied whether the endogenous melatonin patterns in adult patients with developmental brain disorders have any role in response to exogenous melatonin given as a sleep-promoting medicine.

METHODS

: Participants included 15 adults (18-60 years, five females) with developmental brain disorders of varying etiologies, motor handicaps, and long-term history of sleep problems. According to the 24-h patterns of serum melatonin, patients were divided into two subgroups: lower and higher secretors. The pretreatment sleep disorder was characterized by a structured interview, 24-h ambulatory polysomnography and 7-day wrist actigraphy. Patients received 1, 3, or 6mg fast-release melatonin tablets, each for 4 weeks in increasing order, at a constant time of 30min before the desired sleep onset. Similarly, placebos with different codes were given during 3x4 weeks. The 7-day actigraphy was repeated at the end of each drug period. Outcome measures were six different parameters of non-parametric circadian rhythm analysis. Drug effects and 40 confounding/modulating factors were evaluated by applying two-level regression analyses with co-variables.

RESULTS

: Exogenous melatonin decreased the fragmentation of the rest-activity rhythm, increased the day/night ratio of activity and advanced the onset of rest period. The effects on fragmentation and day/night ratio were more pronounced in the lower than higher secretors of melatonin. Other contributing factors in the drug effects were blindness and some features of the original sleep disorder (disrupted cyclicity of the sleep architecture in polysomnography or reported daytime somnolence).

CONCLUSIONS

: Exogenous melatonin consolidated the fragmented rest-activity in about half of the patients. Low endogenous serum melatonin levels at night predicted improvement by the drug. Higher doses were not more effective than the lowest dose.

Insomnia and sleep disruption: relevance for athletic performance

Insomnia is a common sleep complaint even in young adults and has important daytime consequences. Several subjective and objective tools are recommended to assess the magnitude of the problem and to try to find a cause. Chronic insomnia is often caused by precipitating factors, such as acute stress, work conditions, illness, and travel, and perpetuating factors, such as poor sleep hygiene, anxiety, and medications. Insomnia may have implications in athletic performance resulting from physical and cognitive effects. Several pharmacologic and nonpharmacologic approaches are employed in the management of insomnia that have proven effective for short-term treatment. The pharmacologic approaches include the use of zolpidem and specific GABA agonists, benzodiazepines for specific indications, antidepressants, and melatonin. The nonpharmacologic approaches include stimulus control, sleep restriction, relaxation strategies, and cognitive behavioral therapy.

Sleep-anticipating effects of melatonin in the human brain

Melatonin, the hormone produced nocturnally by the pineal gland, is an endogenous regulator of the sleep-wake cycle. The effects of melatonin on brain activities and their relation to induction of sleepiness were studied in a randomized, double-blind, placebo controlled functional magnetic resonance imaging (fMRI) study. Melatonin, but not placebo, reduced task-related activity in the rostro-medial aspect of the occipital cortex during a visual-search task and in the auditory cortex during a music task. These effects correlated with subjective measurements of fatigue. In addition, melatonin enhanced the activation in the left parahippocampus in an autobiographic memory task. Results demonstrate that melatonin modulates brain activity in a manner resembling actual sleep although subjects are fully awake. Furthermore, the fatigue inducing effect of melatonin on brain activity is essentially different from that of sleep deprivation thus revealing differences between fatigues related to the circadian sleep regulation as opposed to increased homeostatic sleep need. Our findings highlight the role of melatonin in priming sleep-associated brain activation patterns in anticipation of sleep.

Daily illumination exposure and melatonin: influence of ophthalmic dysfunction and sleep duration

BACKGROUND

Ocular pathology lessens light's efficacy to maintain optimal circadian entrainment. We examined whether ophthalmic dysfunction explains unique variance in melatonin excretion of older adults over and above the variance explained by daily illumination, medical, and sociodemographic factors. We also examined whether ophthalmic dysfunction influences relationships between ambient illumination and melatonin.

METHODS

Thirty older adults (mean age = 69 years; Blacks = 42% and Whites = 58%) of both genders participated in the study. Demographic and health data were collected at baseline. Participants underwent eye exams at SUNY Downstate Medical Center, wore an actigraph to monitor illumination and sleep, and collected urine specimens to estimate aMT6s concentrations.

RESULTS

Hierarchical regression analysis showed that illumination factors explained 29% of the variance in aMT6s mesor. The proportion of variance explained by ophthalmic factors, sleep duration, and race was 10%, 2%, and 2%, respectively. Illumination factors explained 19% of the variance in aMT6s acrophase. The proportion of variance explained by ophthalmic factors, sleep duration, and race was 11%; 17%; and 2%, respectively. Controlling for sleep duration and race reduced the correlations between illumination and melatonin, whereas controlling for ophthalmic factors did not.

CONCLUSION

Ophthalmic exams showed that elevated intraocular pressure and large cup-to-disk ratios were independently associated with earlier melatonin timing. Lower illumination exposure also had independent associations with earlier melatonin timing. Conceivably, ophthalmic and illumination factors might have an additive effect on the timing of melatonin excretion, which in turn might predispose individuals to experience early morning awakenings.

Melatonin and sleep in aging population

The neurohormone melatonin is released from the pineal gland in close association with the light-dark cycle. There is a temporal relationship between the nocturnal rise in melatonin secretion and the 'opening of the sleep gate' at night. This association, as well as the sleep promoting effect of exogenous melatonin, implicates the pineal product in the physiological regulation of sleep. Aging is associated with a significant reduction in sleep continuity and quality. A decreased production of melatonin with age is documented in a majority of studies. Diminished nocturnal melatonin secretion with severe disturbances in sleep/wake rhythm has been consistently reported in Alzheimer's disease (AD). A recent survey on the effects of melatonin in sleep disturbances, including all age groups, failed to document significant and clinically meaningful effects of exogenous melatonin on sleep quality, efficiency and latency. However, in clinical trials involving elderly insomniacs and AD patients suffering from sleep disturbances exogenous melatonin has repeatedly been found to be effective in improving sleep. The results indicate that exogenous melatonin is more effective to promote sleep in the presence of a diminished production of endogenous melatonin. A MT1/MT2 receptor analog of melatonin (ramelteon) has recently been introduced as a new type of hypnotics with no evidence of abuse or dependence.