Josephine Arendt

Josephine Arendt
University of Surrey · Faculty of Health and Medical Sciences

PhD

About

279
Publications
25,290
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13,264
Citations

Publications

Publications (279)
Article
Full-text available
Last year melatonin was 60 years old, or at least its discovery was 60 years ago. The molecule itself may well be almost as old as life itself. So it is time to take yet another perspective on our understanding of its functions, effects and clinical uses. This is not a formal review—there is already a multitude of systematic reviews, narrative revi...
Article
Full-text available
For many years now a treatment mitigating the debilitating effects of jet lag has been sought. Rapid travel across time zones leads, in most people, to temporary symptoms, in particular poor sleep, daytime alertness and poor performance. Mis-timed circadian rhythms are considered to be the main factor underlying jet-lag symptoms, together with the...
Chapter
Many aspects of human physiology, metabolism, and behavior are dominated by 24-h circadian rhythms including the sleep–wake cycle, alertness and performance patterns, and some hormones. These rhythms are spontaneously generated by an internal circadian clock in the brain and daily light exposure to the eyes synchronizes the clock with the external...
Chapter
Advanced, delayed, free-running and irregular sleep-wake rhythm disorders
Article
Living for extended periods in Antarctica exposes base personnel to extremes of daylength (photoperiod) and temperature. At the British Antarctic Survey base of Halley, 75(0)S, the sun does not rise for 110 d in the winter and does not set for 100 d in summer. Photoperiod is the major time cue governing the timing of seasonal events such as reprodu...
Article
Full-text available
Circadian (∼ 24 hour) timing systems pervade all kingdoms of life, and temporally optimize behaviour and physiology in humans. Relatively recent changes to our environments, such as the introduction of artificial lighting, can disorganize the circadian system, from the level of the molecular clocks that regulate the timing of cellular activities to...
Article
There are conflicting reports regarding seasonal sleep difficulties in polar regions. Herein we report differences in actigraphic sleep measures between two summer trials (collected at Canadian Forces Station Alert, 82.5°N, in 2012 and 2014) and evaluate exogenous melatonin for preventing/treating circadian phase delay due to nocturnal light exposu...
Article
Full-text available
The seasonal extremes of photoperiod in the high Arctic place particular strain on the human circadian system, which leads to trouble sleeping and increased feelings of negative affect in the winter months. To qualify for our study, potential participants had to have been at Canadian Forces Station (CFS) Alert (82° 30’ 00” N) for at least two weeks...
Article
Melatonin (N-acetyl-5-methoxytryptamine) is synthesised largely in the pineal gland at night with a marked circadian rhythm, driven by a central 'clock' the suprachiasmatic nuclei of the hypothalamus. Light suppresses production and synchronises the rhythm to 24. h. Melatonin signals time of day and time of year to body physiology by its profile of...
Article
Full-text available
AimsPreterm infants are deprived of the normal intra-uterine exposure to maternal melatonin and may benefit from replacement therapy. We conducted a pharmacokinetic study to guide potential therapeutic trials. Methods Melatonin was administered to 18 preterm infants in doses ranging from 0.04-0.6gkg(-1) over 0.5-6h. Pharmacokinetic profiles were an...
Article
Full-text available
At Arctic and Antarctic latitudes, personnel are deprived of natural sunlight in winter and have continuous daylight in summer: light of sufficient intensity and suitable spectral composition is the main factor that maintains the 24-h period of human circadian rhythms. Thus, the status of the circadian system is of interest. Moreover, the relativel...
Article
Jet lag is a recognized circadian rhythm disorder characterized by nighttime insomnia, daytime sleepiness, gastrointestinal complaints, and poor mood following rapid travel across multiple time zones. Jet lag manifests from desynchronization between internal rhythms and external time cues. The symptoms often remain for several days until the body c...
Article
Full-text available
To determine the prevalence of self-reported circadian-related sleep disorders, sleep medication and melatonin use in the New Zealand blind population. A telephone survey incorporating 62 questions on sleep habits and medication together with validated questionnaires on sleep quality, chronotype and seasonality. PARTICIPANTS WERE GROUPED INTO: (i)...
Article
Delayed sleep phase (and sometimes free-run) is common in the Antarctic winter (no natural sunlight) and optimizing the artificial light conditions is desirable. This project evaluated sleep when using 17,000 K blue-enriched lamps compared with standard white lamps (5000 K) for personal and communal illumination. Base personnel, 10 males, five fema...
Technical Report
Full-text available
In response to operational difficulties resulting from the effects of fatigue (secondary to jetlag and shiftlag) on performance of Air Force personnel, the Air Force funded a 4-year project to optimize CF ability to manipulate circadian rhythms forwards or backwards to counter jetlag and shiftlag. This report presents the highlights of that work an...
Article
Full-text available
Melatonin and light treatment are recommended for hastening adaptation to time zone change. We evaluated an afternoon regimen of 3 mg sustained release (SR) melatonin with and without next morning green light treatment for circadian phase advance. Effects of melatonin and light were tested separately and then combined to determine if the total phas...
Data
Bland-Altman statistics for period measurements. For each subject, average period length (in vivo and in vitro) is plotted against the difference between the two measurements, expressed in standard deviations from the mean. (0.11 MB TIF)
Data
Comparison of fibroblast period length measured at 36.5 degrees C and at 37.0 degrees C incubator temperature. A. Period length was measured from skin fibroblasts of blind and sighted subjects (from Guildford and Novosibirsk) at two different incubator temperatures, and plotted in comparison. Most subjects showed a similar augmentation in period at...
Article
Full-text available
Diurnal behavior in humans is governed by the period length of a circadian clock in the suprachiasmatic nuclei of the brain hypothalamus. Nevertheless, the cell-intrinsic mechanism of this clock is present in most cells of the body. We have shown previously that for individuals of extreme chronotype ("larks" and "owls"), clock properties measured i...
Article
Subjects working a 12 h offshore night shift for 2 weeks normally adapt to the night shift and are out of synchrony when they return home to day life, with consequent problems of poor sleep. The aim of this study was to investigate the effectiveness of timed light treatment to hasten circadian adaptation and improve sleep after the night shift. Ten...
Article
Full-text available
The internal circadian clock adapts slowly, if at all, to rapid transitions between different shift schedules. This leads to misalignment (desynchrony) of rhythmic physiological systems, such as sleep, alertness, performance, metabolism and the hormones melatonin and cortisol, with the imposed work-rest schedule. Consequences include sleep deprivat...
Article
Full-text available
Melatonin is recommended for hastening adaptation to phase shift, but there is little information on appropriate formulations. We evaluated the efficacy of three melatonin formulations for circadian phase advance and delay: (a) 3 mg regular release (RR), (b) 3 mg sustained release (SR), and (c) 3 mg surge-sustained release (SSR; consisting of 1 mg...
Article
Full-text available
Jet lag degrades performance and operational readiness of recently deployed military personnel and other travelers. The objective of the studies reported here was to determine, using a narrow bandwidth light tower (500 nm), the optimum timing of light treatment to hasten adaptive circadian phase advance and delay. Three counterbalanced treatment or...
Article
Melatonin is an evolutionarily conserved molecule that serves a time-keeping function in various species. In vertebrates, melatonin is produced predominantly by the pineal gland with a marked circadian rhythm that is governed by the central circadian pacemaker (biological clock) in the suprachiasmatic nuclei of the hypothalamus. High levels of mela...
Article
Jet lag is due to the misalignment of the internal circadian clock(s) with external time cues. For short stopovers (1-2 days) adapting the circadian system is not advised, and at present immediate circadian adaptation is virtually impossible. The use of short-term measures such as judicious naps, caffeine and short acting hypnotics to maintain aler...
Article
Full-text available
SUMMARY  The pineal hormone melatonin has clear circadian phase-shifting effects in humans which have recently been formalized as a phase response curve. Its potential use in circadian rhythm disorders has been investigated in field studies of jet lag and shift work and in simulated phase shift. A substantial amount of information indicates that in...
Article
The pineal hormone melatonin is able to shift the timing of circadian rhythms, including the sleep-wake cycle, and to promote sleep. Melatonin agonists with similar properties have therapeutic potential for the treatment of circadian rhythm sleep disorders. Depression is specifically targeted by agomelatine, which is also a serotonin-2C (5-HT(2C))...
Article
6 normal volunteers were required to maintain a regular sleep/wake schedule for one week prior to exposure of moderately bright light during the following periods on three consecutive days in December: Day (D)l: 2000–0200h, D2: 2200–0400h and D3:2400–0800h followed by 8h of darkness (< 1 lux). On D4 subjects returned to their normal environment. Du...
Article
Full-text available
The hormone melatonin is increasingly used for the treatment of certain sleep disorders, particularly those related to disturbed biological rhythms. This article summarises current knowledge of its mechanism of action and identifies situations where there is good evidence for its efficacy. The authors provide advice, based on their own experience a...
Article
Antarctic Base personnel live for 3 months in winter with no natural sunlight. This project compared sleep, by actigraphy, during periods of increased exposure to white light or blue enriched light in 2003. The primary aim was to help define the optimum spectral composition and intensity of artificial environmental light. Nine men and one woman (33...
Article
Blind people report disturbances in alertness, mood and performance. In laboratory studies, these waking functions can only be maintained when the wake-dependent deterioration is opposed by appropriately-timed endogenous circadian rhythms. We aimed to quantify whether variations in waking function experienced by blind people living in society were...
Article
Full-text available
Complaints concerning sleep are high among those who work night shifts; this is in part due to the disturbed relationship between circadian phase and the timing of the sleep-wake cycle. Shift schedule, light exposure, and age are all known to affect adaptation to the night shift. This study investigated circadian phase, sleep, and light exposure in...
Article
People who are blind, in addition to having to cope with partial or no sight, have an added handicap; the transmission of ocular light from the retina to their circadian clock is impaired. At its worse, for example in people with both eyes enucleated, this lesion results in desynchronisation of the biological clock (located in the hypothalamic supr...
Article
Full-text available
The Canadian Forces has initiated a multiple study project to optimize circadian phase changes using appropriately timed phototherapy and/or ingestion of melatonin for those personnel on long-range deployments and shift workers. The work reported here compared four phototherapeutic devices for efficacy in effecting circadian phase delays. In a part...
Article
Heart rate (HR) and heart rate variability (HRV) undergo marked fluctuations over the 24-h day. Although controversial, this 24-h rhythm is thought to be driven by the sleep-wake/rest-activity cycle as well as by endogenous circadian rhythmicity. We quantified the endogenous circadian rhythm of HR and HRV and investigated whether this rhythm can be...
Article
Full-text available
Many aspects of human physiology and behavior are dominated by 24-hour circadian rhythms that have a major impact on our health and well-being, including the sleep-wake cycle, alertness and performance patterns, and many daily hormone profiles. These rhythms are spontaneously generated by an internal "pacemaker" in the hypothalamus, and daily light...
Article
Full-text available
Ocular light plays a key role in human physiology by transmitting time of day information. The production of the pineal gland hormone melatonin is under the control of the light-dark cycle. Its profile of secretion defines biological night and it has been called the 'darkness hormone'. Light mediates a number of non-visual responses, such as phase...
Article
Numerous factors influence the increased health risks of seamen. This study investigated sleep (by actigraphy) and the adaptation of the internal clock in watch-keeping crew compared to day workers, as possible contributory factors. Fourteen watch keepers, 4 h on, 8 h off (0800-1200/2000-2400 h, 1200-1600/2400-0400 h, 1600-2000/0400-0800 h) (fixed...
Article
In humans a range of non-image-forming (NIF) light responses (melatonin suppression, phase shifting and alertness) are short wavelength sensitive (440-480 nm). The aim of the current study was to assess the acute effect of three different short wavelength light pulses (420, 440 and 470 nm) and 600 nm light on subjective alertness. Healthy male subj...
Article
Melatonin signals time of day and time of year in mammals by virtue of its pattern of secretion, which defines 'biological night.' It is supremely important for research on the physiology and pathology of the human biological clock. Light suppresses melatonin secretion at night using pathways involved in circadian photoreception. The melatonin rhyt...
Article
Full-text available
Melatonin is of great importance to the investigation of human biological rhythms. Its rhythm in plasma or saliva provides the best available measure of the timing of the internal circadian clock. Its major metabolite 6-sulphatoxymelatonin is robust and easily measured in urine. It thus enables long-term monitoring of human rhythms in real-life sit...
Article
Melatonin, hormone of the pineal gland, is concerned with biological timing. It is secreted at night in all species and in ourselves is thereby associated with sleep, lowered core body temperature, and other night time events. The period of melatonin secretion has been described as 'biological night'. Its main function in mammals is to 'transduce'...
Article
Full-text available
The rhythm of plasma melatonin originating from the pineal gland and driven by the circadian pacemaker located in the suprachiasmatic nucleus is closely associated with the circadian (approximately 24 h) variation in sleep propensity and sleep spindle activity in humans. We investigated the contribution of melatonin to variation in sleep propensity...
Article
Exogenous melatonin (0.5-10 mg) has been shown to entrain the free-running circadian rhythms of some blind subjects. The aim of this study was to assess further the entraining effects of a daily dose of 0.5 mg melatonin on the cortisol rhythm and its acute effects on subjective sleep in blind subjects with free-running 6-sulphatoxymelatonin (aMT6s)...
Article
Full-text available
The pineal hormone melatonin is a popular treatment for sleep and circadian rhythm disruption. Melatonin administered at optimal times of the day for treatment often results in a prolonged melatonin profile. In photoperiodic (day length-dependent) species, changes in melatonin profile duration influence the timing of seasonal rhythms. We investigat...
Article
Full-text available
Time-dependent variations in the hormonal and metabolic responses to food are of importance to human health, as postprandial metabolic responses have been implicated as risk factors in a number of major diseases, including cardiovascular disease. Early work reported decreasing glucose tolerance in the evening and at night with evidence for insulin...
Article
Full-text available
To investigate the link between extreme diurnal preference, delayed sleep phase syndrome, and a length polymorphism in Per3. Subjects were genotyped using polymerase chain reaction. Subjects with defined diurnal preference as determined by the Horne-Ostberg questionnaire and patients with delayed sleep phase syndrome. The Per3 polymorphism correlat...
Article
The photoreceptor(s) responsible for photoresetting of the human circadian system have not been identified. The aim of the present study was to assess the ability of short wavelength light to alter the timing of circadian rhythms. Eleven male subjects were studied in 15 4-day trials with a single 4 h light pulse administered on day 3, immediately a...
Article
Full-text available
to determine whether melatonin will improve quality of sleep in healthy older people with age-related sleep maintenance problems. a double blind randomised placebo controlled crossover trial in healthy older volunteers. a largely urban population, Auckland, New Zealand. participants were part of the larger Possible Role of Melatonin in Sleep of Eld...
Article
Mutations in clock genes are associated with abnormal circadian parameters, including sleep. An association has been reported previously between a polymorphism (3111C), situated in the 3'-untranslated region (3'-UTR) of the circadian gene Clock and evening preference. In the present study, this polymorphism was assessed in: (1) 105 control subjects...
Article
The light levels required to maintain human circadian phase in the absence of other strong time cues are not defined. We investigated circadian phase in two groups of men, living in partial temporal isolation, exposed to 12 h:12 h light:dark cycles of: (A) 200: <8 lux, broad spectrum white light for 14 days; and (B) 1000: <8lux for 14 days. The rhy...
Article
Nature is the international weekly journal of science: a magazine style journal that publishes full-length research papers in all disciplines of science, as well as News and Views, reviews, news, features, commentaries, web focuses and more, covering all branches of science and how science impacts upon all aspects of society and life.
Article
Full-text available
To determine whether older people with age-related sleep maintenance problems have significantly lower melatonin levels than comparable normal sleepers. Case-control study. A largely urban population, Auckland, New Zealand. People over the age of 65 years, who either slept normally, or had age-related sleep maintenance problems. Participants were r...
Article
The circadian rhythms of many night-shift workers are maladapted to their imposed behavioural schedule, and this factor may be implicated in the increased occurrence of cardiovascular disease (CVD) reported in shift workers. One way in which CVD risk could be mediated is through inappropriate hormonal and metabolic responses to meals. This study in...