THE EFFECTS OF ALCOHOL AND PARTIAL SLEEP LOSS ON DRIVING SIMULATOR PERFORMANCE AND COGNITION

Master'sMASTER OF SOCIAL SCIENCE

Effects of Exposure to Intermittent versus Continuous Red Light on Human Circadian Rhythms, Melatonin Suppression, and Pupillary Constriction

Exposure to light is a major determinant of sleep timing and hormonal rhythms. The role of retinal cones in regulating circadian physiology remains unclear, however, as most studies have used light exposures that also activate the photopigment melanopsin. Here, we tested the hypothesis that exposure to alternating red light and darkness can enhance circadian resetting responses in humans by repeatedly activating cone photoreceptors. In a between-subjects study, healthy volunteers (n = 24, 21–28 yr) lived individually in a laboratory for 6 consecutive days. Circadian rhythms of melatonin, cortisol, body temperature, and heart rate were assessed before and after exposure to 6 h of continuous red light (631 nm, 13 log photons cm−2 s−1), intermittent red light (1 min on/off), or bright white light (2,500 lux) near the onset of nocturnal melatonin secretion (n = 8 in each group). Melatonin suppression and pupillary constriction were also assessed during light exposure. We found that circadian resetting responses were similar for exposure to continuous versus intermittent red light (P = 0.69), with an average phase delay shift of almost an hour. Surprisingly, 2 subjects who were exposed to red light exhibited circadian responses similar in magnitude to those who were exposed to bright white light. Red light also elicited prolonged pupillary constriction, but did not suppress melatonin levels. These findings suggest that, for red light stimuli outside the range of sensitivity for melanopsin, cone photoreceptors can mediate circadian phase resetting of physiologic rhythms in some individuals. Our results also show that sensitivity thresholds differ across non-visual light responses, suggesting that cones may contribute differentially to circadian resetting, melatonin suppression, and the pupillary light reflex during exposure to continuous light

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Circadian phase shift responses to light (h ± SEM).

<p>Circadian phase shift responses are shown for 6 h of exposure to continuous red light, intermittent red light and darkness, or bright white light near the onset of melatonin secretion. By convention, negative values indicate phase delay shifts. Using a linear mixed-effects model for comparing phase resetting responses, bright white light elicited a larger response than either red light condition (<i>P</i><0.003). Phase shifts were similar in response to continuous versus intermittent red light (<i>P</i> = 0.69), and did not differ across physiologic measures (<i>P</i> = 0.35). Data were also analyzed using one-way ANOVA, whereby asterisks (*) indicate significant differences in response to bright white light versus continuous red light, and daggers (^†) indicate significant differences in response to bright white light versus intermittent red light. Phase resetting did not differ between red light conditions.</p

Protocol for assessing circadian phase shift responses and melatonin suppression.

<p>(<b>A</b>) Subjects took part in a 6-day laboratory study. Circadian rhythms were assessed using constant routine (CR) procedures before and after an experimental light exposure session. During the CR procedure, subjects were exposed to <5 lux of ambient light. During the light exposure session, subjects were exposed to 6 h of continuous red light (631 nm, 13 log photons cm⁻² s⁻¹), intermittent red light and darkness (∼1 min on, 1 min off), or bright polychromatic white light (2,500 lux; 4000K) starting 1 h before habitual bedtime. (<b>B</b>) The narrow-bandwidth red light stimulus was generated using a light-emitting diode and delivered to subjects' eyes using a modified Ganzfeld dome. The spectral emission of the LED stimulus is shown.</p

Circadian phase shift responses were similar for exposure to continuous versus intermittent red light.

<p>(<b>A</b>) Circadian responses are shown for individual subjects exposed to 6 h of continuous red light, intermittent red light and darkness, or bright white light. Circadian phase shifts are shown for melatonin (MLT), cortisol (Cort), core body temperature (CBT), forehead skin temperature (FST), and heart rate (HR). By convention, negative values show phase delay shifts. Horizontal lines show the grand mean for each light exposure condition, with the corresponding values shown at the top of the plot. (<b>B</b>) Most subjects exposed to continuous red light exhibited a small resetting response (left), but one participant showed a phase delay shift comparable in magnitude to bright white light exposure (right). (<b>C</b>) Likewise, in response to intermittent red light and darkness, circadian phase measured before and after light exposure was similar in most subjects (left); however one subject showed a large phase delay shift (right). In <b>B</b> and <b>C</b>, representative subjects are shown, with the circadian rhythm of core body temperature (CBT) shown before and after exposure to light (black and gray traces, respectively). Vertical lines show the timing of the fitted minimum for the CBT rhythm. Phase shift values are shown at the top of each plot, and the corresponding subject code is shown on the bottom right.</p

Melatonin levels and pupillary constriction during nocturnal light exposure.

<p>(<b>A</b>) Melatonin profiles are shown for participants exposed to 6 h of continuous red light (left), intermittent red light and darkness (center), or bright white light (right) near the onset of melatonin secretion. Black traces show the melatonin rhythm on the day prior to light exposure, and gray traces show melatonin on the day of the light exposure session. Melatonin concentrations during light exposure were individually adjusted using Z-score values obtained during the first constant routine procedure. Vertical dotted lines indicate the onset and offset of the light exposure session. (<b>B</b>) The area under the curve (AUC) of the melatonin profile during light exposure is shown for each subject, expressed as a percentage of his AUC measured in dim light. Values less than 100% therefore indicate light-induced melatonin suppression, whereas values that exceed 100% indicate that the AUC was higher during the light exposure session relative to the AUC measured in dim light on the previous day. The open circles show responses for subjects <i>crl30</i> and <i>irl31</i>, who exhibited substantial resetting of circadian rhythms, as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096532#pone-0096532-g003" target="_blank">Figure 3</a>. (<b>C</b>) The pupillary light reflex is shown during the first 50 min of exposure to continuous red light (left), alternating red light and darkness (center), and bright white light (right). (<b>D</b>) The median pupillary light response is shown for individual subjects during the 50-min fixed gaze period, expressed relative to the dark pupil. Horizontal dotted lines in <b>C</b> and <b>D</b> indicate pupil diameter in darkness, and data in <b>C</b> are binned at intervals of 15.625 s, corresponding to one-quarter of an intermittent lights-on pulse. In <b>A</b> and <b>C</b>, the mean ± SEM is shown. In <b>B</b> and <b>D</b>: crl, continuous red light; irl, intermittent red light; bwl, bright white light.</p

Erratum to: Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition) (Autophagy, 12, 1, 1-222, 10.1080/15548627.2015.1100356

non present