Exposure to real-ambient bedroom light at night delayed circadian rhythm in healthy Chinese young adults: A cross-sectional study

BACKGROUND

Light at night (LAN) have attracted increased research attention on account of its widespread health hazards. However, the underlying mechanism remains unknown. The objective of this study was to investigate the effects of real-ambient bedroom LAN exposure on circadian rhythm among young adults and potential sex differences.

METHODS

Bedroom LAN exposure was measured at 60-s intervals for 2 consecutive days using a portable illuminance meter. Circadian phase was determined by the dim light melatonin onset (DLMO) time in 7 time-series saliva samples.

RESULTS

The mean age of the 142 participants was 20.7 ± 0.8 years, and 59.9% were women. The average DLMO time was 21:00 ± 1:11 h, with men (21:19 ± 1:12 h) later than women (20:48 ± 1:07 h). Higher level of LAN intensity (LANavg ≥ 3lx vs. LANavg < 3lx) was associated with an 81.0-min later in DLMO time (95% CI: 0.99, 1.72), and longer duration of nighttime light intensity ≥ 5lx (LAN5; LAN5 ≥ 45 min vs. LAN5 < 45 min) was associated with a 51.6-min later in DLMO time (95% CI: 0.46, 1.26). In addition, the delayed effect of LAN exposure on circadian phase was more pronounced in men than in women (all P-values <0.05).

CONCLUSIONS

Overall, bedroom LAN exposure was significantly associated with delayed circadian rhythm. Additionally, the delayed effect is more significant in men. Keeping bedroom dark at night may be a practicable option to prevent circadian disruption and associated health implications. Future studies with more advanced light measurement instrument and consensus methodology for DLMO assessment are warranted.

Distribution of dim light melatonin offset (DLMOff) and phase relationship to waketime in healthy adults and associations with chronotype

OBJECTIVES

Dim light melatonin onset, or the rise in melatonin levels representing the beginning of the biological night, is the gold standard indicator of circadian phase. Considerably less is known about dim light melatonin offset, or the decrease in melatonin to low daytime levels representing the end of the biological night. In the context of insufficient sleep, morning circadian misalignment, or energy intake after waketime but before dim light melatonin offset, is linked to impaired insulin sensitivity, suggesting the need to characterize dim light melatonin offset and identify risk for morning circadian misalignment.

METHODS

We examined the distributions of dim light melatonin offset clock hour and the phase relationship between dim light melatonin offset and waketime, and associations between dim light melatonin offset, phase relationship, and chronotype in healthy adults (N = 62) who completed baseline protocols measuring components of the circadian melatonin rhythm and chronotype.

RESULTS

74.4% demonstrated dim light melatonin offset after waketime, indicating most healthy adults wake up before the end of biological night. Later chronotype (morningness-eveningness, mid-sleep on free days corrected, and average mid-sleep) was associated with later dim light melatonin offset clock hour. Later chronotype was also associated with a larger, positive phase relationship between dim light melatonin offset and waketime, except for morningness-eveningness.

CONCLUSIONS

These findings suggest morning circadian misalignment risk among healthy adults, which would not be detected if only dim light melatonin onset were assessed. Chronotype measured by sleep timing may better predict this risk in healthy adults keeping a consistent sleep schedule than morningness-eveningness preferences. Additional research is needed to develop circadian biomarkers to predict dim light melatonin offset and evaluate appropriate dim light melatonin offset timing to promote health.

Correlation of Circadian Rhythms and Improvement of Depressive Symptoms in Acute Ischemic Stroke Patients

OBJECTIVES

To investigate the correlation between evening melatonin timing secretion, dim light melatonin onset (DLMO), and post-stroke depression (PSD) in acute ischemic stroke (AIS) patients and their influence on the improvement of depressive symptoms.

MATERIALS AND METHODS

120 patients with a recent magnetic resonance imaging confirmed stroke were included. Salivary melatonin samples were collected at 5 time points within 1 week after hospitalization (7 p.m.-11 p.m., 1 sample per hour). The circadian phase was defined by calculating DLMO secretion. Post-stroke depressive symptoms were evaluated by the 17-item Hamilton Rating Scale for Depression (HRSD) both on day 7 of hospitalization and 3 months after stroke. Patients were divided into PSD and non-PSD groups based on whether the acute phase HRSD score was ≥8. Similarly, patients were divided into the improved depressive symptoms (IDS) and no improvement in depressive symptoms (non-IDS) groups based on whether the HRSD score at 3 months was lower than at baseline. Neurological recovery at 3 months was assessed using the modified Rankin Scale (mRS).

RESULTS

The difference in DLMO between PSD and non-PSD patients was not statistically significant (p =0.173). In the non-IDS group, there was a significant decrease in melatonin secretion at 10 p.m. (p =0.012), and DLMO was significantly later than in the IDS group (p =0.017). Logistic regression analysis showed that DLMO (OR 1.91, 95%CI:1.13-3.23, p = 0.016) was an independent risk factor for persistent no improvement in depressive symptoms, which was associated with a markedly worse prognosis (p <0.001).

CONCLUSION

Our findings suggest possible interventions for the very early identification of non- IDS patients.

What a difference a year makes: Objective rest/activity patterns, circadian phase markers, and sleep quality before and during the COVID-19 pandemic

OBJECTIVES

The COVID-19 pandemic led to numerous changes in sleep duration, quality, and timing. The goal of this study was to examine objective and self-reported changes in sleep and circadian timing before and during the pandemic.

METHODS

Data were utilized from an ongoing longitudinal study of sleep and circadian timing with assessments at baseline and 1-year follow-up. Participants had baseline assessment between 2019 and March 2020 (before pandemic) and 12-month follow-up between September 2020 and March 2021 (during pandemic). Participants completed 7 days of wrist actigraphy, self-report questionnaires, and laboratory-collected circadian phase assessment (dim light melatonin onset).

RESULTS

Actigraphy and questionnaire data were available for 18 participants (11 women and 7 men, Mean = 38.8 years, SD = 11.8). Dim light melatonin onset was available for 11 participants. Participants demonstrated statistically significant decreases in sleep efficiency (Mean = -4.11%, SD = 3.22, P = .001), worse scores on Patient-Reported Outcome Measurement Information System sleep disturbance scale (Mean increase = 4.48, SD = 6.87, P = .017), and sleep end time delay (Mean = 22.4 mins, SD = 44.4 mins, P = .046). Chronotype was significantly correlated with change in dim light melatonin onset (r = 0.649, P = .031). This suggests that a later chronotype is associated with a greater delay in dim light melatonin onset. There were also non-significant increases in total sleep time (Mean = 12.4 mins, SD = 44.4 mins, P = .255), later dim light melatonin onset (Mean = 25.2 mins, SD = 1.15 hrs, P = .295), and earlier sleep start time (Mean = 11.4 mins, SD = 48 mins, P = .322).

CONCLUSION

Our data demonstrate objective and self-reported changes to sleep during the COVID-19 pandemic. Future studies should look at whether some individuals will require intervention to phase advance sleep when returning to previous routines such as returning to office and school settings.

Dim light melatonin patterns in unaffected offspring of parents with bipolar disorder: A case-control high-risk study

BACKGROUND

Circadian dysregulation has long been thought to be a key component in the pathophysiology of bipolar disorder (BD). However, it remains unclear whether this dysregulation constitutes a risk factor, manifestation, or consequence of BD. This study aimed to compare dim light melatonin secretion patterns between unaffected offspring of parents with BD (OBD) and offspring of control parents (OCP).

METHODS

This case-control study included unaffected OBD (mean age 14.0 years; male 50.0 %) and age- and sex-matched OCP (mean age 13.0 years; male: 43.5 %). Seventeen saliva samples were collected in dim light conditions. Dim light melatonin onset (DLMO), phase angles, and area under the curve (AUC) were calculated.

RESULTS

185 saliva samples from 12 OBD (n = 12) and 741 from OCP (n = 46) were collected. Unaffected OBD had a significant lower nocturnal melatonin level (14.8 ± 4.6 vs. 20.3 ± 11.7 pg/mL) and a smaller melatonin AUC within two hours after DLMO (35.5 ± 11.3 vs. 44.6 ± 18.1 pg/mL) but a significant larger phase angle between DLMO and sleep onset (2.2 ± 1.0 vs. 1.4 ± 1.2 h) than OCP. There was no significant between-group difference in DLMO. The graphic illustrations showed a considerably flattened melatonin secretion in unaffected OBD.

LIMITATIONS

The main limitations include lack of 24-h dim melatonin secretion measurement, large age range of participants, and small sample size.

CONCLUSIONS

These findings suggest that unaffected OBD already presented with circadian rhythm dysregulations. Future investigations are needed to clarify the role of abnormal melatonin secretion in the onset of BD.

Assessment of dim light melatonin onset based on plasma and saliva samples

Melatonin (MELA) is a nocturnal hormone involved in the regulation of the circadian rhythm. MELA can be detected in plasma and saliva, and its salivary concentration strongly correlates with its plasma concentration. Dim light melatonin onset (DLMO) is considered to be the most accurate objective marker for assessing the circadian phase. The purpose of the study was to establish a method for the determination of MELA in plasma and saliva based on the liquid chromatography with tandem mass spectrometry (LC-MS/MS) and compare DLMO using both plasma and saliva matrices. The validation of the LC-MS/MS methods was performed in accordance with the European Medicines Agency (EMA) guideline. The study was conducted on a group of 21 volunteers, male and females, aged 26-54 years. Plasma and saliva were collected at five time points: between 20:00 and 00:00 hours. The MELA concentration was determined by the LC-MS/MS. The DLMO was considered as the point in time when MELA concentration exceeds 20 pg/mL in plasma and 7 pg/mL in saliva. The correlation coefficient between the plasma and salivary MELA concentration was r = 0.764 (p < .001). The ratio of the plasma/saliva MELA concentrations was 2.87. The mean time of the DLMO in the plasma was 21:30 ± 0:45 hours, and in the saliva was as follows: 21:34 ± 1:00 hours. The correlation between the DLMO, calculated based on the plasma and saliva MELA profiles, was r = 0.679 (p < .05). The determination of salivary MELA concentration using LC-MS/MS allows for the determination of the DLMO. Our method may be applied in clinical practice for the diagnosis and monitoring of circadian rhythm disorders.Abbreviations: CE: Collision Energy; CID: Collision-Induced Dissociation; DL: Desolvation Module; DLMO: Dim Light Melatonin Onset; EFSA: European Food Safety Authority; EMA: European Medicines Agency; ESI: electrospray ionization; HB: heat block; HPLC: high performance liquid chromatography; IS: internal standard; K₃EDTA: ethylenediaminetetraacetic acid tripotassium salt; LC-MS/MS: liquid chromatography with tandem mass spectrometry; LLE: liquid-liquid extraction; LLOQ: lower limit of quantification; MELA: melatonin; MELA-D₄: melatonin-d₄; MRM: multiple reaction monitoring; Q1: quadrupole 1; Q3: quadrupole 3; RE: relative error; RIA: radioimmunoassay; RSD: relative standard deviation; SD: standard deviation; ULOQ: upper limit of quantification.

Delayed Sleep-Wake Phase Disorder: Can Polysomnography Be Useful?

BACKGROUND

Delayed sleep-wake phase disorder (DSWPD) is a chronic condition with a multifactorial etiology that primarily affects adolescents, significantly influencing their quality of life. In clinical practice, the contribution of intrinsic and behavioral factors is difficult to determine. The aim of our study was to compare data from clinical interviews, sleep diaries, actigraphy, and nocturnal polysomnography (PSG) in a cohort of adolescents with DSWPD and to assess psychiatric/neurodevelopmental comorbidity.

METHODS

Thirty-one patients (22 male; mean age 15.4 ± 2.2 years, range 12 to 19 years) with a diagnosis of DSWPD based on detailed history, sleep diary, and actigraphy underwent nocturnal polysomnography (PSG) and neurological, psychological, and psychiatric examination.

RESULTS

Attention-deficit/hyperactivity disorder (ADHD) was present in 14 cases (45%), specific learning difficulties in nine (29%), and mood disorder (anxiety/depression) in 16 patients (52%). PSG revealed sleep-onset delay in only 12 (38%) cases. No differences in clinical data or psychiatric comorbidity between the group with sleep delay and the group with normal sleep onset were detected. Decreased total sleep time, sleep efficiency, rapid eye movement (REM) sleep, and prolonged REM sleep latency were observed in patients with delayed sleep onset.

CONCLUSIONS

PSG showed delayed sleep timing in only 38% of patients with a diagnosis of DSWPD based on diagnostic criteria of the International Classification of Sleep Disorders. We suggest that PSG can provide useful information regarding the prevailing etiology (biological versus behavioral) if dim light melatonin onset testing is not available.

Sleep duration and timing in obsessive-compulsive disorder (OCD): evidence for circadian phase delay

OBJECTIVES

To investigate potential delays in endogenous melatonin in individuals with obsessive-compulsive disorder (OCD).

METHODS

First, data are presented for 15 individuals with OCD and matched healthy controls. Next, nine additional participants with OCD who did not have matched controls were added, resulting in a sample of 24 individuals with OCD. All participants were assessed for sleep and circadian rhythm disturbance. Dim light melatonin onset (DLMO) was derived from salivary melatonin and was used in conjunction with sleep diaries, interview measures, and questionnaires. A subset of the OCD group (n = 16) also used actigraphy.

RESULTS

In sum, 42% percent (10/24) of the patients with OCD met the criteria for delayed sleep-wake phase disorder (DSWPD) in comparison to 0% in the control sample. DLMO was significantly later in individuals with OCD compared to controls. DLMO and bedtime were not significantly associated with the severity of obsessive-compulsive symptoms or negative affect.

CONCLUSIONS

Replication of the findings presented herein, particularly the DLMO results, is warranted. Further, there are now three studies showing that nearly ½ of individuals with OCD meet criteria for a DSWPD. Future studies can explore the mechanisms underlying these connections and the implications of this comorbidity. These findings may increase our understanding of OCD and inform future interventions.

Melatonin-Measurement Methods and the Factors Modifying the Results. A Systematic Review of the Literature

Melatonin plays an important role in regulating the sleep-wake cycle and adaptation to environmental changes. Concentration measurements in bioliquids such as serum/plasma, saliva and urine are widely used to assess peripheral rhythm. The aim of the study was to compare methods and conditions of determinations carried out with the identification of factors potentially affecting the measurements obtained. We have identified a group of modifiable and unmodifiable factors that facilitate data interpretation. Knowledge of modifiers allows you to carefully plan the test protocol and then compare the results. There is no one universal sampling standard, because the choice of method and biofluid depends on the purpose of the study and the research group.

Assessment of Circadian Rhythms

Circadian rhythms are observed in most physiologic functions across a variety of species and are controlled by a master pacemaker in the brain called the suprachiasmatic nucleus. The complex nature of the circadian system and the impact of circadian disruption on sleep, health, and well-being support the need to assess internal circadian timing in the clinical setting. The ability to assess circadian rhythms and the degree of circadian disruption can help in categorizing subtypes or even new circadian rhythm disorders and aid in the clinical management of the these disorders.

Correcting delayed circadian phase with bright light therapy predicts improvement in ADHD symptoms: A pilot study

Attention-deficit/hyperactivity disorder (ADHD) is a common condition with comorbid insomnia reported in >70% of children and adults. These patients demonstrate delays in sleep-wake rhythms, nocturnal rise in melatonin, and early morning rise in cortisol. Given that standard psychopharmacologic treatments for ADHD often do not completely control symptoms in participants with circadian rhythm delay, we sought to test whether bright light therapy (BLT) advances circadian rhythms and further reduces ADHD symptoms over standard treatments. In addition to standard of care, participants with ADHD diagnosis underwent 1 week of baseline assessment followed by 2-weeks of 30-min morning 10,000-lux BLT beginning 3 h after mid-sleep time. Participants minimized overhead light after 4 p.m., wore an actigraphy watch, and recorded BLT time on daily sleep logs. Dim Light Melatonin Onset (DLMO) was assessed at baseline and after 2-week treatment. ADHD symptoms were measured by the ADHD-Rating Scales (ADHD-RS). BLT significantly advanced the phase of DLMO by 31 min [mean time (SEM), 20:36 (0:21) advanced to 20:05 (0:20)] and mid-sleep time by 57 min [4:37 (0:22) advanced to 3:40 (0:16); paired t-tests, p = 0.002 and 0.004, respectively). Phase advances (in DLMO or mid-sleep time) were significantly correlated with decreased ADHD-RS total scores (p = 0.027 and 0.044) and Hyperactive-Impulsive sub-scores (p = 0.014 and 0.013, respectively). Actigraphy analysis for a subset of 8 participants with significant DLMO phase advance revealed no significant changes in total sleep time, sleep efficiency, wake after sleep onset, or percent wake during sleep interval. This is the first successful use of BLT for advancing melatonin phase and improving ADHD symptoms in adults. BLT may be a complementary treatment for both delayed sleep timing and ADHD symptoms in adults.

Can tryptophan supplement intake at breakfast enhance melatonin secretion at night?

Background

Tryptophan (TRP) is an essential amino acid, and it has been suggested that TRP intake at breakfast combined with daytime bright light exposure can increase nocturnal melatonin secretion. However, the mechanisms involved are not yet clear. The aim of this study was to examine the effect of TRP supplement intake at breakfast on nocturnal melatonin secretion under different daytime light intensities in humans.

Method

Twelve subjects (aged 21.3 ± 3.0 years, mean ± standard deviation) participated in a random order in experimental sessions lasting 3 days under four conditions in a laboratory setting. The four conditions were TRP*Bright, Placebo*Bright, TRP*Dim, and Placebo*Dim. A TRP capsule (1000 mg) or a placebo starch capsule (1000 mg) were taken at breakfast. In addition, during the daytime (07:00–18:00), the subjects were asked to stay under different light intensities: >5000 lx (bright) or <50 lx (dim). Saliva samples were collected for measuring the concentration of melatonin. The time courses of melatonin concentration and dim light melatonin onset (DLMO) were compared among the four conditions using repeated measurements analysis of variance (ANOVA).

Result

Nocturnal melatonin concentrations in the bright light condition tended to be higher than in the dim light condition (main effect of light: p = .099). Moreover, in the bright light condition, the change in DLMO between baseline and after the intervention was significantly higher than that in the dim light condition (main effect of light: p <.001). However, the ANOVA results indicated no significant effect of TRP intake on melatonin secretion.

Conclusion

Our findings indicated that intake of 1000 mg of TRP at breakfast on 1 day did not change nocturnal melatonin secretion, even though TRP is the precursor of melatonin. In contrast, daytime bright light exposure increased nocturnal melatonin secretion and advanced the phase of melatonin onset. Therefore, TRP supplementation, unlike exposure to daytime bright light, does not acutely affect biological rhythm and sleep in humans.

Trial registration

UMIN Clinical Trial Registry: UMIN000024121

Electronic supplementary material

The online version of this article (doi:10.1186/s40101-017-0135-9) contains supplementary material, which is available to authorized users.

Estimating the dim light melatonin onset of adolescents within a 6-h sampling window: the impact of sampling rate and threshold method

OBJECTIVE/BACKGROUND

Circadian rhythm sleep-wake disorders (CRSWDs) often manifest during the adolescent years. Measurement of circadian phase such as the dim light melatonin onset (DLMO) improves diagnosis and treatment of these disorders, but financial and time costs limit the use of DLMO phase assessments in clinic. The current analysis aims to inform a cost-effective and efficient protocol to measure the DLMO in older adolescents by reducing the number of samples and total sampling duration.

PATIENTS/METHODS

A total of 66 healthy adolescents (26 males) aged 14.8-17.8 years participated in a study; they were required to sleep on a fixed baseline schedule for a week before which they visited the laboratory for saliva collection in dim light (<20 lux). Two partial 6-h salivary melatonin profiles were derived for each participant. Both profiles began 5 h before bedtime and ended 1 h after bedtime, but one profile was derived from samples taken every 30 min (13 samples) and the other from samples taken every 60 min (seven samples). Three standard thresholds (first three melatonin values mean + 2 SDs, 3 pg/mL, and 4 pg/mL) were used to compute the DLMO. An agreement between DLMOs derived from 30-min and 60-min sampling rates was determined using Bland-Altman analysis; agreement between the sampling rate DLMOs was defined as ± 1 h.

RESULTS AND CONCLUSIONS

Within a 6-h sampling window, 60-min sampling provided DLMO estimates within ± 1 h of DLMO from 30-min sampling, but only when an absolute threshold (3 or 4 pg/mL) was used to compute the DLMO. Future analyses should be extended to include adolescents with CRSWDs.

Sleep and the endogenous melatonin rhythm of high arctic residents during the summer and winter

The seasonal extremes of photoperiod in high latitudes place particular strain on the human circadian system. Arctic residence has been associated with poor sleep in both summer and winter. The goal of the work reported here was to study the circadian rhythms of individuals living in the high Arctic by measuring sleep variables and the timing of melatonin production. Two research trials were conducted in the built environment of CFS Alert (82° 29' 58″ N). Participants wore motion logging devices (actigraphs), which measure ambient light as well as motion, for 1week to provide data on sleep quantity, quality and light exposure. On the penultimate day of each trial, the participants were maintained together in a gymnasium with lounge chairs and saliva was collected at regular intervals to measure melatonin and assess the dim light melatonin onset (DLMO), offset (MelOFF), 50% rise and fall times of the whole profile and total production. In general, sleep duration was found to be significantly different between the January and June data collections at CFS Alert, with participants in June sleeping 50min on average less each day compared to their January counterparts. In June sleep was mistimed in many subjects relative to circadian phase as evidenced by the melatonin rhythm. Exposure to bright evening light was the most likely causal factor and should be avoided in the Arctic summer. The Arctic summer represents a particularly challenging environment for obtaining sufficient sleep. This has implications for the cognitive performance of staff during work hours.

Sleep deficits in the High Arctic summer in relation to light exposure and behaviour: use of melatonin as a countermeasure

BACKGROUND

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 exposure.

METHODS

Subjects wore actigraphs continuously to obtain sleep data. Following seven days of actigraphic recording the subjects filled out questionnaires regarding sleep difficulty and psychosocial parameters and subsequently remained in dim light conditions for 24 hours, during which saliva was collected bihourly to measure melatonin. During Trial 2, individuals who reported difficulty sleeping were prescribed melatonin, and a second saliva collection was conducted to evaluate the effect of melatonin on the circadian system.

RESULTS

Trial 1 subjects collectively had late dim light melatonin onsets and difficulty sleeping; however, the Trial 2 subjects had normally timed melatonin rhythms, and obtained a good quantity of high-quality sleep. Nocturnal light exposure was significantly different between the trials, with Trial 1 subjects exposed to significantly more light between 2200 and 0200h. Melatonin treatment during Trial 2 led to an improvement in the subjective sleep difficulty between the pre- and post-treatment surveys; however there were no significant differences in the objective measures of sleep.

CONCLUSIONS

The difference in sleep and melatonin rhythms between research participants in June 2012 and June 2014 is attributed to the higher levels of nocturnal light exposure in 2012. The avoidance of nocturnal light is likely to improve sleep during the Arctic summer.

The effects of chronotype, sleep schedule and light/dark pattern exposures on circadian phase

BACKGROUND

Chronotype characterizes individual differences in sleep/wake rhythm timing, which can also impact light exposure patterns. The present study investigated whether early and late chronotypes respond differently to controlled advancing and delaying light exposure patterns while on a fixed, advanced sleep/wake schedule.

METHODS

In a mixed design, 23 participants (11 late chronotypes and 12 early chronotypes) completed a 2-week, advanced sleep/wake protocol twice, once with an advancing light exposure pattern and once with a delaying light exposure pattern. In the advancing light exposure pattern, the participants received short-wavelength light in the morning and short-wavelength-restricting orange-tinted glasses in the evening. In the delaying light exposure pattern, participants received short-wavelength-restricting orange-tinted glasses in the morning and short-wavelength light in the evening. Light/dark exposures were measured with the Daysimeter. Salivary dim light melatonin onset (DLMO) was also measured.

RESULTS

Compared to the baseline week, DLMO was significantly delayed after the delaying light intervention and significantly advanced after the advancing light intervention in both groups. There was no significant difference in how the two chronotype groups responded to the light intervention.

CONCLUSIONS

The present results demonstrate that circadian phase changes resulting from light interventions are consistent with those predicted by previously published phase response curves (PRCs) for both early and late chronotypes.