Association between light exposure at night and manic symptoms in bipolar disorder: cross-sectional analysis of the APPLE cohort

ABSTRACT

Previous studies have found that keeping the room dark at night was associated with a decrease in manic symptoms for patients with bipolar disorder (BD). However, the association between light at night of real-life conditions and manic symptoms is unclear. We investigated the association between bedroom light exposure at night and manic symptoms in BD patients. One-hundred and eighty-four outpatients with BD participated in this cross-sectional study. The average light intensity at night during sleep was evaluated using a portable photometer for seven consecutive nights. Manic symptoms were assessed using the Young Mania Rating Scale (YMRS), and scores ≥5 were treated as a “hypomanic state.” The median (interquartile range) YMRS score was 2.0 (0–5.0), and 52 (28.2%) participants were in a hypomanic state. The prevalence of a hypomanic state was significantly higher in the participants with an average light intensity at night exposure of ≥3 lux than in those with <3 lux (36.7% versus 21.9%; P = .02). In multivariable logistic regression analysis adjusted for BD type, depressive symptoms, sleep duration, and daytime physical activity, the odds ratio (OR) for a hypomanic state was significantly higher for the participants with an average light intensity at night exposure of ≥3 lux than for those with <3 lux (OR: 2.15, 95% confidence interval: 1.09–4.22, P = .02). This association remained significant at the cutoff value of YMRS score ≥6 (OR: 2.51, 95% confidence interval: 1.15–5.46; P = .02). The findings of this study indicate bedroom light exposure at night is significantly associated with manic symptoms in BD patients. Although the results of this cross-sectional investigation do not necessarily imply causality, they may serve to inform beneficial nonpharmacological intervention and personalized treatment of BD patients.     

Actigraphic estimates of sleep and the sleep-wake rhythm,and 6-sulfatoxymelatonin levels in healthy Dutch children

ABSTRACT

Sleep and the sleep-wake rhythm are essential for children’s health and well-being, yet reference values are lacking. This study therefore aimed to assess actigraphic estimates of sleep and the 24-h sleep-wake rhythm, as well as 6-sulfatoxymelatonin (aMT6s) levels in healthy children of different age groups. Additionally, relationships between the outcomes and sex, highest parental educational level (as an indication of socioeconomic status (SES)), and body-mass-index (BMI) were explored. In this cross-sectional study, healthy Dutch children (2–18 years) wore an actigraph (GT3x) for 7 consecutive days, collected first-morning void urine and completed a sleep log and sociodemographic questionnaire. Actigraphically estimated sleep variables were sleep onset latency (SOL), sleep efficiency (SE), total sleep time (TST), and wake after sleep onset (WASO). Non-parametric sleep-wake rhythm variables were intradaily variability (IV); interdaily stability (IS); the activity counts and timing of the least active 5-h period (L5counts and midpoint) and of the most active 10-h period (M10 counts and midpoint); and the relative amplitude (RA), i.e. the ratio of the difference and the sum of M10 and L5 counts. Finally, creatinine-corrected aMT6s levels were obtained by isotope dilution mass spectrometry. Effects of age group (preschool 2–5 years/school-aged 6–12 years/teenager 13–18 years), sex, highest parental educational level and BMI (Z-scores) were explored. Ninety-four children participated, equally divided across age groups (53% boys). Teenagers slept less, but more efficiently, than younger children, while their 24 h sleep-wake rhythm was the least stable and most fragmented (likely due to fragmentation of daytime activity). Additionally, aMT6s levels significantly declined over the age groups. Children from highly educated parents had lower sleep efficiency, but a more stable sleep-wake rhythm. Finally, sex or increase in BMI was not associated with any of the outcomes in this study. In conclusion, this study provides reference values of healthy children across different age groups and different sociodemographic factors. In the future, this information may help to better interpret outcomes in clinical populations.     

Coupling Neuropeptide Levels to Structural Plasticity in Drosophila Clock Neurons

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The protective effect of cycloastragenol on aging mouse circadian rhythmic disorder induced by d-galactose

Aging process in mammals is associated with a decline in amplitude and a long period of circadian behaviors which are regulated by a central circadian regulator in the suprachiasmatic nucleus (SCN) and local oscillators in peripheral tissues. It is unclear whether enhancing clock function can retard aging. Using fibroblasts expressing per2::lucSV and senescent cells, we revealed cycloastragenol (CAG), a natural aglycone derivative from astragaloside IV, as a clock amplitude enhancing small molecule. CAG could activate telomerase to antiaging, but no reports focused on its effects on circadian rhythm disorders in aging mice. Here we analyze the potential effects of CAG on d -galactose-induced aging mice on the circadian behavior and expression of clock genes. For this purpose, CAG (20 mg/kg orally), was administered daily to d -galactose (150 mg/kg, subcutaneous) mice model of aging for 6 weeks. An actogram analysis of free-running activity of these mice showed that CAG significantly enhances the locomotor activity. We further found that CAG increase expressions of per2 and bmal1 genes in liver and kidney of aging mouse. Furthermore, CAG enhanced clock protein BMAL1 and PER2 levels in aging mouse liver and SCN. Our results indicated that the CAG could restore the behavior of circadian rhythm in aging mice induced by d -galactose. These data of present study suggested that CAG could be used as a novel therapeutic strategy for the treatment of age-related circadian rhythm disruption.     

White and Amber Light at Night Disrupt Sleep Physiology in Birds

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Mice Reach Higher Visual Sensitivity at Night by Using a More Efficient Behavioral Strategy

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COVID-19 and “natural” experiments arising from physical distancing: a hypothetical case study from chronobiology

ABSTRACT

With countless “natural” experiments triggered by the COVID-19-associated physical distancing, one key question comes from chronobiology: “When confined to homes, how does the reduced exposure to natural daylight arising from the interruption of usual outdoor activities plus lost temporal organization ordinarily provided from workplaces and schools affect the circadian timing system (the internal 24 h clock) and, consequently, health of children and adults of all ages?” Herein, we discuss some ethical and scientific facets of exploring such natural experiments by offering a hypothetical case study of circadian biology.     

Circadian communication between unicells?

Populations ofGonyaulax polyedra, in two different phases, about 11 h apart, were mixed, and the intensity of their spontaneous bioluminescence glow recorded for about 2 wk under conditions of constant dim (35±3 μE/m²/s) white light and constant temperature (19.0±0.3°C). The phases and amplitudes of glow signals recorded from mixed cultures were compared with those obtained from the arithmetic sum of the intensity data from two control vials. Peaks in control cultures generally remained separate, but there was a spontaneous increase in the period beginning 6–11 d after the onset of constant conditions. This did not occur in cultures in which the medium was exchanged with fresh medium every 2 d. In the actual mixes of two cultures there was a merging of the two subpeaks in the signal, which did not occur when the medium was exchanged. The results indicate that conditioning of the medium by cells may affect the period of the circadian rhythm and that this might result in a type of communication. Supported by the Deutsche Forschungsgemeinschaft; present address     

Chronobiologic Factors in Experimental Stress Ulcer

The available literature on chronobiologic factors in experimental stress ulcer is extremely small and thematically limited. It focuses almost exclusively on circadian rhythms and, within that, on rhythms related to light-dark cycles, activity and body temperature. Among these, only differences in ulcer induction related to circadian activity patterns have been adequately demonstrated. Other circadian patterns and other temporal phase relationships might be profitably explored, including those related to postnatal development. It is also likely that the important relationships between biorhythms and stress ulcer are not limited to ulcer induction. Future studies should address chronobiologic factors in predisposition, severity of illness, the probability of recovery and response to various therapeutic interventions.