Working Under Daylight Intensity Lamp: An Occupational Risk for Developing Circadian Rhythm Sleep Disorder?

Relationship of activities outside work to sleep and depression/anxiety disorders in Korean workers: the 4th Korean working condition survey

BACKGROUND

Sleep disorders and depression/anxiety disorders are long-standing and significant problem for mental health. Also there are already known so many negative health effect of these disorders. But there were few studies to examine the association between activities outside work and forementioned disorders. So this study aimed the association of those things by using the Republic of Korean data.

METHODS

Data from 32,232 wage workers were used in the 4th Korean Working Condition Survey. General and occupational characteristics, sleep disorders, depression/anxiety disorders and activities outside work are included in questionnaire. To find the relationship between activities outside work and sleep, depression/anxiety disorders, multivariate logistic regression analysis was used after adjusting for general and occupational characteristics.

RESULTS

We observed that volunteer activities increased the odds ratio of both sleep disorders and depression/anxiety disorders(Odds ratio[OR] = 1.35, 95% confidence interval[CI]: 1.03-1.78 and OR = 1.54, 95% CI: 1.29-1.84, respectively). And self-development activities increase the odds ratio of sleep disorders(OR = 1.35, 95% CI: 1.17-1.57). Gardening activities lowered the odds ratio of depression/anxiety disorders(OR = 0.74, 95% CI: 0.59-0.94).

CONCLUSION

Some of activities outside work were related to sleep disorders and depression/anxiety disorders among Korean wage workers. Our results showed negative health effect of some kinds of activities outside work such as volunteering and self-devlopment compared to other studies that emphasized positive effect of those activities for health.

Circadian disruption: New clinical perspective of disease pathology and basis for chronotherapeutic intervention

Biological processes are organized in time as innate rhythms defined by the period (τ), phase (peak [Φ] and trough time), amplitude (A, peak-trough difference) and mean level. The human time structure in its entirety is comprised of ultradian (τ < 20 h), circadian (20 h > τ < 28 h) and infradian (τ > 28 h) bioperiodicities. The circadian time structure (CTS) of human beings, which is more complicated than in lower animals, is orchestrated and staged by a brain central multioscillator system that includes a prominent pacemaker - the suprachiasmatic nuclei of the hypothalamus. Additional pacemaker activities are provided by the pineal hormone melatonin, which circulates during the nighttime, and the left and right cerebral cortices. Under ordinary circumstances this system coordinates the τ and Φ of rhythms driven by subservient peripheral cell, tissue and organ clock networks. Cyclic environmental, feeding and social time cues synchronize the endogenous 24 h clocks and rhythms. Accordingly, processes and functions of the internal environment are integrated in time for maximum biological efficiency, and they are also organized and synchronized in time to the external environment to ensure optimal performance and response to challenge. Artificial light at night (ALAN) exposure can alter the CTS as can night work, which, like rapid transmeridian displacement by air travel, necessitates realignment of the Φ of the multitude of 24 h rhythms. In 2001, Stevens and Rea coined the phrase "circadian disruption" (CD) to label the CTS misalignment induced by ALAN and shift work (SW) as a potential pathologic mechanism of the increased risk for cancer and other medical conditions. Current concerns relating to the effects of ALAN exposure on the CTS motivated us to renew our long-standing interest in the possible role of CD in the etiopathology of common human diseases and patient care. A surprisingly large number of medical conditions involve CD: adrenal insufficiency; nocturia; sleep-time non-dipping and rising blood pressure 24 h patterns (nocturnal hypertension); delayed sleep phase syndrome, non-24 h sleep/wake disorder; recurrent hypersomnia; SW intolerance; delirium; peptic ulcer disease; kidney failure; depression; mania; bipolar disorder; Parkinson's disease; Smith-Magenis syndrome; fatal familial insomnia syndrome; autism spectrum disorder; asthma; byssinosis; cancers; hand, foot and mouth disease; post-operative state; and ICU outcome. Poorly conceived medical interventions, for example nighttime dosing of synthetic corticosteroids and certain β-antagonists and cyclic nocturnal enteral or parenteral nutrition, plus lifestyle habits, including atypical eating times and chronic alcohol consumption, also can be causal of CD. Just as surprisingly are the many proven chronotherapeutic strategies available today to manage the CD of several of these medical conditions. In clinical medicine, CD seems to be a common, yet mostly unrecognized, pathologic mechanism of human disease as are the many effective chronotherapeutic interventions to remedy it.

Phase advance with separate and combined melatonin and light treatment

INTRODUCTION

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 phase change is additive or synergistic.

MATERIAL AND METHODS

For each condition (melatonin, placebo, light, melatonin plus light), 11 subjects spent from Tuesday evening until Friday afternoon in the laboratory. For all four conditions, the following sleep schedule was maintained: night 1, 2345 to 0630 hours, night 2, 1600 to 0530 hours, and night 3, 2345 to 0700 hours. For the light-only condition, light treatment was administered between 0700 and 0800 hours on Thursday. For melatonin-only or placebo conditions, capsules were administered at 1600 hours on Wednesday. For the combined condition, melatonin was administered at 1600 hours on Wednesday with light treatment between 0600 and 0700 hours on Thursday. Circadian phase was assessed by calculating dim light melatonin onset (DLMO) from salivary melatonin, using a mean baseline +2 standard deviations (BL+2 SD) threshold. For all four conditions, pre-treatment and post-treatment DLMO assessments were on Tuesday and Thursday evenings, respectively.

RESULTS

Phase advances were: melatonin at 1600 hours, 0.72 h p<0.005, light treatment from 0700 to 0800 hours, 0.31 h, non-significant, and the combined treatment, 1.04 h p<0.0002.

CONCLUSION

The phase advance from the combination of afternoon melatonin with next morning light is additive.

Melatonin in the multi‐oscillatory mammalian circadian world

In mammals, the complex interaction of neural, hormonal, and behavioral outputs from the suprachiasmatic nucleus (SCN) drives circadian expression of events, either directly or through coordination of the timing of peripheral oscillators. Melatonin, one of the endocrine output signals of the clock, provides the organism with circadian information and can be considered as an endogenous synchronizer, able to stabilize and reinforce circadian rhythms and to maintain their mutual phase-relationship at the different levels of the circadian network. Moreover, exogenous melatonin, through an action on the circadian clock, affects all levels of the circadian network. The molecular mechanisms underlying this chronobiotic effect have also been investigated in rats. REV-ERB alpha seems to be the initial molecular target.

[Sleep disorders and hypnotic agents: medical, social and economical impact]

Insomnia is a subjective complaint relating to approximately 30% of the adult population in France, described by the patient as a difficulty of initiating and/or maintaining sleep. Its prevalence increases with age and sex: women are more affected than men (24% vs 14%). Insomnia is either occasional (20%), or chronic (10%). Chronic insomnia has an important impact on patients' everyday life e.g. fatigue, perturbed diurnal waking state, impaired quality-of-life... which results in lower work productivity and drowsiness as well as relational difficulties, absenteeism. About 80% of patients consult their general practitioner first. The aim of a hypnotic agent is to obtain sleep as physiological as possible. Benzodiazepines and benzodiazepines-like agents (zopiclone, zolpidem, zaleplon) are the most widely used hypnotics. However, their indications must be limited to occasional insomnia with a limited duration: less than four weeks. There is no advantage with using a combination of hypnotic agents, a practice which should be prohibited. Adverse effects can be serious, e.g. diurnal somnolence associated with risks of road accidents and, in the elderly, the risk of falls. After chronic use, hypnotics can be addictive, as their effects wear off in three to four weeks. After withdrawal, insomnia rebound is frequent. Use of hypnotics in association with alcohol is a well-known drug-addiction behavior. According to the French health insurance fund, 9% of the general population use hypnotics and about half of them regularly. Insurance refunds for hypnotics and sedatives reach more than 110 million euros annually. The efficiency of hypnotics wears off, quickly for benzodiazepines (three - four weeks), or less quickly for zopiclone and zolpidem (a few months). Insomnia is a major public health issue, each year 10% of the incident cases of insomnia treated by hypnotics joint the group of subjects with chronic insomnia. This failure to treat insomnia properly can be explained, at least in part, by several insufficiencies: physicians and pharmacists training, medical profession awareness, research, public information on the rules of good sleep (public health campaigns, booklets, role of physicians and the pharmacists).

Promoting adjustment of the sleep–wake cycle by chronobiotics

Chronobiotics are substances that adjust the timing of internal biological rhythms. Many classes of drugs have been claimed to possess such properties and arouse growing interest as the circumstances for their use in sleep disturbances caused by circadian rhythms alterations (delayed or advanced sleep-phase syndromes, non-24-h sleep-wake disorders, jet lag, shift work sleep disorders and so on) have become progressively more frequent. Amongst the substances potentially presenting chronobiotic properties, a consensus seems to be reached on the possible use of melatonin or its agonists to shift the phase of the human circadian clock, but optimizing the dose, formulation and especially the time of administration require further studies.