Abstract: We examined whether dynamically changing light across a scheduled 16-h waking day influences sleepiness, cognitive performance, visual comfort, melatonin secretion, and sleep under controlled laboratory conditions in healthy men. Fourteen participants underwent a 49-h laboratory protocol in a repeated-measures study design. They spent the first 5-h in the evening under standard lighting, followed by an 8-h nocturnal sleep episode at habitual bedtimes. Thereafter, volunteers either woke up to static light or to a dynamic light that changed spectrum and intensity across the scheduled 16-h waking day. Following an 8-h nocturnal sleep episode, the volunteers spent another 11-h either under static or dynamic light. Static light attenuated the evening rise in melatonin levels more compared to dynamic light as indexed by a significant reduction in the melatonin AUC prior to bedtime during static light only. Participants felt less vigilant in the evening during dynamic light. After dynamic light, sleep latency was significantly shorter in both the baseline and treatment night while sleep structure, sleep quality, cognitive performance and visual comfort did not significantly differ. The study shows that dynamic changes in spectrum and intensity of light promote melatonin secretion and sleep initiation in healthy men.
Keywords: Human health; Lighting; cognition; humans; male; melatonin; non-visual effects of light; sleep; wakefulness
Abstract: OBJECTIVE: Sleep disturbance, a core feature of bipolar disorder, is associated with residual mood symptoms, mood episode recurrence and suicide ideation. We investigated the effect of evening light exposure on sleep in patients with bipolar disorder. METHODS: In this longitudinal analysis, we measured the sleep parameters of 207 outpatients with bipolar disorder using actigraphy at their homes for seven consecutive nights. We measured the white-light illuminance and the irradiance of each wavelength during the 4 hours before each participant's bedtime. We used mixed-effect linear regression analysis for repeated measures to evaluate the effect of evening light exposure on subsequent sleep parameters. RESULTS: The median white-light illuminance was 25.8 lux (interquartile range, 12.9-50.1 lux). In a multivariable model adjusted for potential confounders, we found higher white-light illuminance to be significantly associated with lower sleep efficiency (per log lux: 95% confidence interval = [-1.328, -0.133]; p = 0.017), prolonged sleep-onset latency (95% confidence interval = [0.006, 0.172]; p = 0.035) and longer wake after sleep onset (95% confidence interval = [1.104, 4.459]; p = 0.001). This effect size was larger in the younger age group (aged < 44 years) stratified by median age. Higher irradiance of the blue wavelength range was significantly associated with longer wake after sleep onset, a result similar to those for the green and red wavelength ranges. CONCLUSION: We observed significant associations between evening light exposure and subsequent sleep in patients with bipolar disorder. The effects of various light wavelengths on sleep in bipolar disorder require further investigation.
Keywords: Human Health; Bipolar disorder; actigraphy; circadian rhythm; evening light; sleep
Abstract: AIMS: Identify the prevalence of circadian health disorders in ICU and hospitalized patients. Stablish the relationship of the circadian system with light, temperature, noise and nursing activities. BACKGROUND: Commonly, self-assessment through subjective questionnaires is used for research about sleep quality. However, more reliable and valid measures should be applied objectively to find out the real prevalence of the problem. There is a negative relationship between circadian rhythms and hospitalization. In this study, we will analyse sleep patterns and hospital environments to implement measures to improve the quality of care related to sleep. DESIGN: Descriptive observational study. It is estimated that 975 patients from 13 hospitals need to be recruited from ICU and hospitalization units. The sample should meet the following criteria: Patients over 18 admitted to ICU and medical units, length of stay between 96-148 hr, with no visual, hearing or moderate-severe cognitive impairment. Variables: Sleep variables are collected with an electronic device (named Kronowise(R) and Kronobed(R)), circadian and infrared light exposure, environmental noise, temperature, unit structural characteristics, nursing care (from 0 to 6 a.m.) and, characteristics of hospitalization period. The study, registered on Clinical Trials, initiated in December 2019 and it will continue up to December 2022. DISCUSSION: Using objective and subjective measures of sleep and circadian rhythms, this study will shed light on the factors that negatively affect the hospitalized patients' sleep quality and circadian health. The ultimate goal is to design hospital guidelines to minimize the adverse effects on the dependent variables studied. Arguably, these guidelines will contribute to reducing the risk of these alterations and it will also serve to improve the nursing activities. CONCLUSION: We expect to obtain adequate results for the creation of a protocol to improve the circadian health, quality of care and health outcomes related to sleep in patients.
Keywords: Human Health; care; circadian rhythm; hospitalization; light; noise; nursing; nursing activities; protocol; sleep quality
Abstract: KEY POINTS: Shift work impairs metabolic health, although its effects during pregnancy are not well understood We evaluated the effects of a simulated shift work protocol for one-third, two-thirds or all of pregnancy on maternal and pregnancy outcomes in sheep. Simulated shift work changed the timing of activity, disrupted hormonal and cellular rhythms, and impaired maternal glucose tolerance during early pregnancy. Gestation length was increased in twin pregnancies, whereas singleton lambs were lighter at a given gestational age if mothers were subjected to shift work conditions in the first one-third of pregnancy. Exposure to rotating night and day shifts, even if only in early pregnancy, may adversely affect maternal metabolic and pregnancy outcomes. ABSTRACT: Shift workers are at increased risk of developing type 2 diabetes and obesity; however, the impact during pregnancy on maternal metabolism is unknown. Using a large animal model, we assessed the impact of simulated shift work (SSW) exposure during pregnancy on maternal circadian rhythms, glucose tolerance and pregnancy outcomes. Following mating, ewes were randomly allocated to a control photoperiod (CON 12 h light, 12 h dark) or to SSW, where the timing of light exposure and food presentation was reversed twice each week for one-third, two-thirds or all of pregnancy. Maternal behaviour followed SSW cycles with increased activity during light exposure and feeding. Melatonin rhythms resynchronized within 2 days of the photoperiod shift, whereas peripheral circadian rhythms were arrhythmic. SSW impaired glucose tolerance (+29%, P = 0.019) and increased glucose-stimulated insulin secretion (+32%, P = 0.018) in ewes with a singleton fetus in early but not late gestation. SSW exposure did not alter rates of miscarriage or stillbirth, although it extended gestation length in twin pregnancies (+2.4 days, P = 0.032). Relative to gestational age, birth weight was lower in singleton progeny of SSW than CON ewes (-476 g, P = 0.016). These results have implications for the large number of women currently engaged in shift work, and further studies are required to determine progeny health impacts.
Abstract: White light-emitting diodes (LEDs) will likely become the most used lighting devices worldwide in the future because of their very low prices over the course of their long lifespans which can be up to several tens of thousands of hours. The expansion of LED use in both urban and domestic lighting has prompted questions regarding their possible health effects, because the light that they provide is potentially high in the harmful blue band (400-500nm) of the visible light spectrum. Research on the potential effects of LEDs and their blue band on human health has followed three main directions: 1) examining their retinal phototoxicity; 2) examining disruption of the internal clock, i.e., an out-of-sync clock, in shift workers and night workers, including the accompanying health issues, most concerningly an increased relative risk of cancer; and 3) examining risky, inappropriate late-night use of smartphones and consoles among children and adolescents. Here, we document the recognized or potential health issues associated with LED lighting together with their underlying mechanisms of action. There is so far no evidence that LED lighting is deleterious to human retina under normal use. However, exposure to artificial light at night is a new source of pollution because it affects the circadian clock. Blue-rich light, including cold white LEDs, should be considered a new endocrine disruptor, because it affects estrogen secretion and has unhealthful consequences in women, as demonstrated to occur via a complex mechanism.