The Effects of a Blue Monochromatic Light Intervention on Evening-type Individuals' Sleep and Circadian Rhythms
试验速览
- 阶段
- 不适用
- 状态
- 已完成
- 入组人数
- 34
- 试验地点
- 1
- 主要终点
- Change scores from baseline to post-intervention in Dim light melatonin onset (DLMO)
研究概览
简要总结
The present project is aimed to contribute with new knowledge concerning how light conditions in the physical environment can be manipulated to alter the sleep and circadian rhythms of individuals with an evening-type circadian rhythm. More precisely, the study will explore whether exposure to blue light (compared to a full spectrum light control condition) during the morning hours advance the circadian rhythms of evening-type individuals, towards that which is more similar to the daily rhythm of morning-type individuals. This study is important as it has been found that evening-type adolescents and adults are at higher risk of poor academic performance and demonstrate lower intellectual performance when tested at their nonoptimal early times of day, and given the fact that most schools and workplaces structure their working hours during such early hours of the day. Such an intervention could thus help evening-type individuals better adjust to the different early day requirements that they are exposed to. The project involves a three-day intervention where participants will be exposed to blue monochromatic light, administered through ceiling mounted light emitting diode (LED)-based room lighting, in the early hours of each morning for a duration of 60 min. The participants' sleep, circadian rhythm and waking function will be assessed both objectively and subjectively. The effects of the intervention are transferable to real life educational and work settings and can thus be applied in naturalistic settings. The intervention is based on the new laboratory infrastructure available at the sleep laboratory situated in Christies gate 12.
详细描述
Background:
Morningness/eveningness is a phenomenon that reflects the tendency to be an "early morning bird" or a "late night owl" and is thus a source of inter-individual variation in timing of sleep and other behaviors. Evening- and morning-type individuals demonstrate differences that derive internally regarding the circadian phase of their endogenous biological clock. A certain group of individuals referred to as morning-type individuals have been consistently found to perform better in the morning, whereas evening-type individuals appear to be more alert and perform better in the evening. Morning-type individuals have earlier bed- and rise times than evening-types, while evening-type individuals have been known to report significantly later bed- and rise-times compared to morning-type individuals. In addition, evening-type adolescents have been known to demonstrate poorer academic and intellectual performances during their nonpreferred, i.e., early hours of the day.
Circadian rhythms are known as biological processes that display endogenous, entrainable oscillations in a period of about 24 hours. These rhythms have been found to be controlled by the circadian pacemaker, which is located in the suprachiasmatic nuclei (SCN) of the hypothalamus. These 24-hour rhythms manifest themselves in an observable manner within numerous physiological measures, such as the sleep-wake cycle, the core body temperature, and the excretion of hormones such as melatonin. The core body temperature falls during the night and reaches its lowest point (nadir) in the early morning, after which it starts to rise again. Melatonin secretion follows a curve which is almost inverse compared to the core body temperature rhythm, and is sensitive to light exposure which inhibits melatonin secretion. Melatonin either in plasma, saliva or urine is regarded as an objective marker of circadian rhythms, of which the dim light melatonin onset (time when melatonin reaches 4 pg/ml in saliva) is the most commonly used parameter.
Sleep is known to be most easily initiated when the core body temperature is falling and as the melatonin level is rising. It is also known to be most easily initiated in a timeframe of six hours before nadir until a couple of hours after nadir of the core body temperature.
Evening-type individuals experience increased sleepiness and poorer performances during the early hours of the morning, as there is a mismatch between their circadian rhythms and their requirement of being awake at such early hours. Sleepiness is known to have severe implications for performance.
研究设计
- 研究类型
- Interventional
- 分配方式
- Randomized
- 干预模型
- Parallel
- 主要目的
- Treatment
- 盲法
- Double (Participant, Investigator)
盲法说明
A third-party investigator is recruited to be present during the intervention. This third-party investigator has no knowledge of the hypotheses of the study.
Although the participants can see the type of light they receive, they have no knowledge of the study hypotheses.
入排标准
- 性别
- All
- 接受健康志愿者
- 是
入选标准
- •Scoring below 42 on the Horne-Östberg Morningness-Eveningness Questionnaire, as this categorizes moderate and definitely evening types (Horne & Östberg, 1976).
排除标准
- •Participants will be excluded if a positive case is indicated on the Mood Disorder Questionnaire (MDQ), indicating the presence or history of bipolar disorder.
- •Participants will also be excluded if they have worked night shifts during the past three months.
研究组 & 干预措施
Blue monochromatic light
Three consecutive mornings of one hour exposure to monochromatic light (20 lx, irradiance = 49.65 µW/cm2) with peak wavelength of 455 nm (blue light), with equal photon flux as the control condition.
干预措施: Blue light exposure (Other)
Full spectrum light control condition
Three consecutive mornings of one hour exposure to full spectrum light (2500 Kelvin, irradiance = 37.72 µW/cm2) with equal photon flux as the blue light.
We will adjust the light intensity to make sure that the photon energy is the same across the two conditions.
干预措施: Full spectrum light exposure (Other)
结局指标
主要结局
Change scores from baseline to post-intervention in Dim light melatonin onset (DLMO)
时间窗: Pre-intervention/baseline (Monday in the week of intervention - one day before the first intervention day); Post-intervention (Friday, the week of intervention - one day after last intervention day)
Melatonin either in plasma, saliva or urine is regarded as an objective marker of circadian rhythms, of which the dim light melatonin onset (time when melatonin reaches 4 pg/ml in saliva) is the most commonly used parameter (Pandi-Perumal et al., 2007). The change score of the intervention group will be compared to the change score of the control group. Thus only one parameter will be estimated.
Psychomotor Vigilance Task (PVT)
时间窗: PVT will be given to participants on the three days of light intervention (Tuesday, Wednesday and Thursday). The average score of these three days will be obtained and compared with the control group.
A 10-minute reaction-time test that provides a measure of sustained attention will be completed by the participants during light exposure in the laboratory. The participant simply responds to stimuli given on a display by pressing a button as soon as possible. PVT is especially sensitive to sleep loss and fatigue (Lamond, Dawson \& Roach, 2005). Average scores of reaction time across Tuesday, Wednesday and Thursday (the three days of light intervention) will be calculated for the intervention group and compared to the average scores of reaction time across Tuesday, Wednesday and Thursday (the three days of light intervention for the control group. Since the comparison is made across days/measurement points, only one composite parameter for each condition will be calculated.
Change scores of Feeling of Morning Wakefulness, measured by Sleep Diary
时间窗: Tuesday, Wednesday and Thursday (baseline; week before intervention); Tuesday, Wednesday and Thursday (week of light intervention)
Change scores of the feeling of morning wakefulness across Tuesday to Thursday the week before intervention, substracted from Feeling of Morning Wakefulness across Tuesday to Thursday on the intervention week. Since the comparison is made across days/measurement points, only one composite parameter for each condition will be calculated.
Karolinska Sleepiness Scale (KSS)
时间窗: Given on the days of intervention (Tuesday, Wednesday, Thursday) twice on each day. First immediately when the participants enter the lab to receive the intervention, and the second after they have received one hour of light, before they leave the lab.
KSS comprises a single item assessing state sleepiness on a scale from 1 (very rested) to 9 (very sleepy). (Aakerstedt \& Gillberg, 1990). The minimum score is 1 (very rested) and the maximum is 9 (very sleepy). Lower values present the feeling of restedness and are thus considered to be a better outcome. Average score of KSS will be calculated across the three intervention days (Tuesday, Wednesday, Thursday) for the intervention group, and compared to the average score of KSS across the same three intervention days for the control group. Accordingly, only one outcome measure will be calculated per group. Thus only one parameter will be estimated.
次要结局
- Change scores in Sleep Onset Time(Change scores of sleep onset time across Tuesday, Wednesday, and Thursday the week before intervention, substracted from sleep onset time across Tuesday, Wednesday, and Thursday on the intervention week.)
- Changes scores in Sleep Length(Change scores of sleep length across Tuesday, Wednesday and Thursday the week before intervention, substracted from sleep length across Tuesday, Wednesday and Thursday on the intervention week.)
- Changes scores in Wake-up Time(Change scores of wake-up time across Tuesday, Wednesday and Thursday the week before intervention, substracted from wake-up time across Tuesday, Wednesday and Thursday on the intervention week.)