Circadian phase-shifting effects of a laboratory environment: a clinical trial with bright and dim light (original) (raw)
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Circadian phase response curves to light in older and young women and men
Journal of Circadian Rhythms, 2007
The phase of a circadian rhythm reflects where the peak and the trough occur, for example, the peak and trough of performance within the 24 h. Light exposure can shift this phase. More extensive knowledge of the human circadian phase response to light is needed to guide light treatment for shiftworkers, air travelers, and people with circadian rhythm phase disorders. This study tested the hypotheses that older adults have absent or weaker phase-shift responses to light (3000 lux), and that women's responses might differ from those of men.
International Journal of Molecular Sciences
Artificial light at night can have negative effects on human wellbeing and health. It can disrupt circadian rhythms, interfere with sleep, and participate in the progress of civilisation diseases. The aim of the present study was to explore if dim artificial light during the entire night (ALAN) can affect melatonin production and sleep quality in young volunteers. We performed two experiments in real-life home-based conditions. Young volunteers (n = 33) were exposed to four nights of one lux ALAN or two nights of five lux ALAN. Melatonin production, based on 6-sulphatoxymelatonin/creatinine concentrations in urine, and sleep quality, based on actimetry, were evaluated. Exposure to ALAN one lux during the entire night did not suppress aMT6s/creatinine concentrations but did aggravate sleep quality by increasing sleep fragmentation and one-minute immobility. ALAN up to five lux reduced melatonin biosynthesis significantly and interfered with sleep quality, as evidenced by an increased...
Behavioral Sleep Medicine, 2003
The endogenous melatonin onset in dim light (DLMO) is a marker of circadian phase that can be used to appropriately time the administration of bright light or exogenous melatonin in order to elicit a desired phase shift. Determining an individual's circadian phase can be costly and time-consuming. We examined the relationship between the DLMO and sleep times in 16 young healthy individuals who slept at their habitual times for a week. The DLMO occurred about 2 hours before bedtime and 14 hours after wake. Wake time and midpoint of sleep were significantly associated with the DLMO (r = 0.77, r = 0.68 respectively), but bedtime was not (r = 0.36). The possibility of predicting young healthy normally entrained people's DLMOs from their sleep times is discussed.
Biological Rhythm Research, 2014
Light, especially its blue component, is the main synchronizer of circadian rhythms. We investigated effects of suppressed blue band of the spectrum on melatonin production and sleep efficiency in 18 young volunteers. During control days, participants lived in their home environment, and next five days in a room lit only by daylight with windows equipped with a filter blocking the blue band of the light spectrum. Light intensity, circadian stimulus and light irradiance were monitored. No significant changes in the daily pattern and total urinary 6-sulphatoxymelatonin excretion were found between control and experimental conditions. Parameters of sleep efficiency measured by wrist actigraphy were not worsened, but neutral chronotypes exhibited shortened sleep duration under light-modified conditions. We conclude that young healthy people can compensate for negative effects of transitory-worsened lighting conditions on their daily rhythms, but chronotypes and other personal characteristics may modify biological responses and should be considered.
Progress in Neuro-Psychopharmacology and Biological Psychiatry, 2007
The circadian rhythm of melatonin in saliva or plasma, or of the melatonin metabolite 6-sulphatoxymelatonin (aMT6S) in urine, is a defining feature of suprachiasmatic nucleus (SCN) function, the endogenous oscillatory pacemaker. A substantial number of studies have shown that, within this rhythmic profile, the onset of melatonin secretion under dim light conditions (the dim light melatonin onset or DLMO) is the single most accurate marker for assessing the circadian pacemaker. Additionally, melatonin onset has been used clinically to evaluate problems related to the onset or offset of sleep. DLMO is useful for determining whether an individual is entrained (synchronized) to a 24-h light/dark (LD) cycle or is in a free-running state. DLMO is also useful for assessing phase delays or advances of rhythms in entrained individuals. Additionally, it has become an important tool for psychiatric diagnosis, its use being recommended for phase typing in patients suffering from sleep and mood disorders. More recently, DLMO has also been used to assess the chronobiological features of seasonal affective disorder (SAD). DLMO marker is also useful for identifying optimal application times for therapies such as bright light or exogenous melatonin treatment.
Scheduled Bright Light for Treatment of Insomnia in Older Adults
Journal of the American Geriatrics Society, 2009
Objectives-To determine if bright light can improve sleep in older individuals with insomnia. Design-Single-blind, placebo-controlled, twelve-week, parallel-group randomized design comparing four treatment groups representing a factorial combination of two lighting conditions and two times of light administration. Setting-At-home light treatment, eight office therapy sessions. Participants-Thirty six females, fifteen males (63.6 ± 7.1 years) meeting primary insomnia criteria, recruited from the community. Interventions-A 12-week program of sleep hygiene and exposure either to bright (∼4000 lux) or dim light (∼65 lux) scheduled daily in the morning or evening for 45 minutes. Measurements and Results-Within group changes were observed for subjective sleep measures (sleep logs, questionnaires) after morning or evening bright light, but were not significantly different from those observed after exposure to scheduled dim light. Objective sleep changes (actigraphy, polysomnography) after treatment were not significantly different between bright and dim light groups. Scheduled light exposure was able to shift circadian phase predictably, but was unrelated to changes in objective or subjective sleep measures. A polymorphism in CLOCK predicted morningness, but did not moderate the effects of light on sleep. The phase angle between the circadian system (melatonin midpoint) and sleep (darkness)
Circadian abnormalities in older adults
Journal of Pineal Research, 2001
This study examined the circadian phase adjustment of symptomatic elders ages 60 -79 years in comparison with that of young, healthy adults ages 20 -40 years. Seventy-two elders with complaints of insomnia or depression, and 30 young, healthy adults were assessed for 5 -7 days at home. Sleep and illumination were recorded with Actillume wrist monitors and sleep diaries. Urine was collected over two 24-hr periods and assayed for 6-sulphatoxymelatonin (6-smt). The volunteers were then observed continuously for 5 nights and 4 days in the laboratory. In the laboratory, sleep periods were fixed at 8 hr with polysomnographic assessment of sleep, apnea-hypopnea, and nocturnal myoclonus. Circadian dispersion, defined as the mean variation of 6-smt acrophase from the median age-specific acrophase, was significantly greater in the older vs. young adults. Likewise, circadian malsynchronization, defined as the absolute number of hours (advance or delay) between the 6-smt acrophase and the middle of the sleep period, was significantly greater in the older vs. young volunteers. For the older volunteers, multiple regressions were calculated associating sleep with potential correlates of sleep disturbance. Nocturnal myoclonus and circadian malsynchronization were more strongly associated with sleep impairment than other factors (e.g., sleep apnea, depression). These observations suggest that circadian malsynchronization might be a common and significant cause of disturbed sleep among adults over age 60.
Journal of Pineal Research, 1994
Different patterns of light exposure in relation to melatonin and cortisol rhythms and sleep of night workers. J. Pineal Res. 1994:16:127-135. Abstract: There is strong evidence to suggest that circadian psychophysiological adaptation processes are modified by light, depending on its intensity and timing. To characterize such modifications and determine whether they are associated with an alteration in the dayhight pattern of melatonin excretion, measurements were obtained around the clock in 14 permanent night workers, each studied over a 48 hr period in the field. The light exposure behavior of these workers was studied with a newly developed light dosimetry by measuring light intensity at eye level. Physical activity was continuously registered and sleep indices were obtained by sleep logs and activity markings. Circadian rhythms of melatonin and cortisol were analysed from salivary samples collected for 24 hr at 2 hr intervals. The interindividual variation of melatonin acrophase determined by cosinor analysis was greater than 180 degrees (from around midnight to noon) and that of cortisol was about 135 degrees (from early morning to afternoon). Hormonal phase positions coincided significantly with light exposure: the more bright light pulses in the morning (maximum lux between 0600 and 0900), the less were the melatonin and cortisol acrophases shifted into the day. There was also a negative correlation between melatonin acrophase shift and duration of the overall light exposure above 1500 lux. Morning light maximum and sleep onset correlated highly significantly. Night workers were divided into those with less than ('non-shifters', n = 9) and more than 6 hr deviation from midnight ('shifters', n = 5) of the melatonin acrophase. The group comparison revealed a marked difference of the mean melatonin concentrations at night, and at 0700. Shifters did not experience bright light exposure in the morning and showed a tendency towards shorter overall exposure of light above 1500 lux. In conclusion, light avoidance behavior during morning hours, as observed in 5 out of 14 night workers, coincided significantly with a phase delay of melatonin acrophase. Light avoidance also correlated with an earlier sleep onset and a tendency to longer sleep hours. Thus our data suggest that the interaction of a phase shifted activity cycle and the lighvdark exposure leads in the field situation to different degrees of adaptation to the prevailing activitykest requirements, depending on dose and phase position of bright light exposure.