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Author (down) Wright, K.P.J.; McHill, A.W.; Birks, B.R.; Griffin, B.R.; Rusterholz, T.; Chinoy, E.D.
Title Entrainment of the human circadian clock to the natural light-dark cycle Type Journal Article
Year 2013 Publication Current Biology : CB Abbreviated Journal Curr Biol
Volume 23 Issue 16 Pages 1554-1558
Keywords Human Health; Adult; Circadian Clocks/*radiation effects; Female; Humans; *Lighting; Male; *Photoperiod; *Sunlight; Young Adult; Circadian Rhythm
Abstract The electric light is one of the most important human inventions. Sleep and other daily rhythms in physiology and behavior, however, evolved in the natural light-dark cycle [1], and electrical lighting is thought to have disrupted these rhythms. Yet how much the age of electrical lighting has altered the human circadian clock is unknown. Here we show that electrical lighting and the constructed environment is associated with reduced exposure to sunlight during the day, increased light exposure after sunset, and a delayed timing of the circadian clock as compared to a summer natural 14 hr 40 min:9 hr 20 min light-dark cycle camping. Furthermore, we find that after exposure to only natural light, the internal circadian clock synchronizes to solar time such that the beginning of the internal biological night occurs at sunset and the end of the internal biological night occurs before wake time just after sunrise. In addition, we find that later chronotypes show larger circadian advances when exposed to only natural light, making the timing of their internal clocks in relation to the light-dark cycle more similar to earlier chronotypes. These findings have important implications for understanding how modern light exposure patterns contribute to late sleep schedules and may disrupt sleep and circadian clocks.
Address Sleep and Chronobiology Laboratory, Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309-0354, USA. kenneth.wright@colorado.edu
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0960-9822 ISBN Medium
Area Expedition Conference
Notes PMID:23910656; PMCID:PMC4020279 Approved no
Call Number LoNNe @ christopher.kyba @ Serial 505
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Author (down) Wright, K.P.J.; Hull, J.T.; Czeisler, C.A.
Title Relationship between alertness, performance, and body temperature in humans Type Journal Article
Year 2002 Publication American Journal of Physiology. Regulatory, Integrative and Comparative Physiology Abbreviated Journal Am J Physiol Regul Integr Comp Physiol
Volume 283 Issue 6 Pages R1370-7
Keywords Human Health; Adult; Attention/*physiology; *Body Temperature; Circadian Rhythm/physiology; Cognition/*physiology; Female; Humans; Male; Memory/physiology; Reaction Time; Sleep/physiology; Time Factors; Wakefulness/physiology; NASA Discipline Regulatory Physiology; Non-NASA Center
Abstract Body temperature has been reported to influence human performance. Performance is reported to be better when body temperature is high/near its circadian peak and worse when body temperature is low/near its circadian minimum. We assessed whether this relationship between performance and body temperature reflects the regulation of both the internal biological timekeeping system and/or the influence of body temperature on performance independent of circadian phase. Fourteen subjects participated in a forced desynchrony protocol allowing assessment of the relationship between body temperature and performance while controlling for circadian phase and hours awake. Most neurobehavioral measures varied as a function of internal biological time and duration of wakefulness. A number of performance measures were better when body temperature was elevated, including working memory, subjective alertness, visual attention, and the slowest 10% of reaction times. These findings demonstrate that an increased body temperature, associated with and independent of internal biological time, is correlated with improved performance and alertness. These results support the hypothesis that body temperature modulates neurobehavioral function in humans.
Address Division of Sleep Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA. kenneth.wright@colorado.edu
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0363-6119 ISBN Medium
Area Expedition Conference
Notes PMID:12388468 Approved no
Call Number LoNNe @ kagoburian @ Serial 835
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Author (down) Wood, B.; Rea, M.S.; Plitnick, B.; Figueiro, M.G.
Title Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression Type Journal Article
Year 2013 Publication Applied Ergonomics Abbreviated Journal Appl Ergon
Volume 44 Issue 2 Pages 237-240
Keywords Adolescent; *Computers, Handheld; Female; Humans; Light/*adverse effects; Male; Melatonin/*biosynthesis; Photoperiod; Saliva/*metabolism; Sleep/radiation effects; Time Factors; Young Adult; melatonin
Abstract Exposure to light from self-luminous displays may be linked to increased risk for sleep disorders because these devices emit optical radiation at short wavelengths, close to the peak sensitivity of melatonin suppression. Thirteen participants experienced three experimental conditions in a within-subjects design to investigate the impact of self-luminous tablet displays on nocturnal melatonin suppression: 1) tablets-only set to the highest brightness, 2) tablets viewed through clear-lens goggles equipped with blue light-emitting diodes that provided 40 lux of 470-nm light at the cornea, and 3) tablets viewed through orange-tinted glasses (dark control; optical radiation <525 nm approximately 0). Melatonin suppressions after 1-h and 2-h exposures to tablets viewed with the blue light were significantly greater than zero. Suppression levels after 1-h exposure to the tablets-only were not statistically different than zero; however, this difference reached significance after 2 h. Based on these results, display manufacturers can determine how their products will affect melatonin levels and use model predictions to tune the spectral power distribution of self-luminous devices to increase or to decrease stimulation to the circadian system.
Address Lighting Research Center, Rensselaer Polytechnic Institute, 21 Union Street, Troy, NY 12180, USA. woodb5@rpi.edu
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0003-6870 ISBN Medium
Area Expedition Conference
Notes PMID:22850476 Approved no
Call Number IDA @ john @ Serial 136
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Author (down) Vollmer, C.; Randler, C.; Di Milia, L.
Title Further evidence for the influence of photoperiod at birth on chronotype in a sample of German adolescents Type Journal Article
Year 2012 Publication Chronobiology International Abbreviated Journal Chronobiol Int
Volume 29 Issue 10 Pages 1345-1351
Keywords Human Health; Adolescent; Child; Circadian Rhythm/*physiology; Female; Germany; Humans; Male; Parturition/*physiology; *Photoperiod; Puberty/physiology; *Seasons; Sleep/*physiology
Abstract Individuals differ in their circadian preferences (chronotype). There is evidence in the literature to support a season-of-birth effect on chronotype but the evidence is not convincing. In part, the relationship is obscured by a number of methodological differences between studies, including the measures used to define morningness, the way in which the seasons were categorized, and the sample size. This study adds to the literature in several ways. First, we adopt a new approach to categorizing the photoperiod rather than the calendar season; thus we prefer to use the term photoperiod at birth. Second, we used two measures of morningness. Third, we used a large and homogeneous German sample. The results show that adolescents (n = 2905) born during the increasing photoperiod (Feb-Apr) had a significantly later midpoint of sleep (MSFsc) than those born during the decreasing photoperiod (Aug-Oct). A similar pattern was found for the Composite Scale of Morningness (CSM). Furthermore, both measures of chronotype demonstrated a significant quadratic function over a 1-yr cycle. When looking at each of six consecutive years separately, the Composite Scale of Morningness suggests a cosine rhythm linked to increasing and decreasing photoperiods that becomes weaker in amplitude with increasing age. Despite the strengths in our study, the effect of photoperiod at birth on chronotype remains small. Future studies may require larger sample sizes, may need to explore how neonatal light exposure modulates chronotype, and may need to track how puberty and adolescent lifestyle habits mask the photoperiod effect.
Address Department of Biology, University of Education Heidelberg, Im Neuenheimer Feld 561-2, Heidelberg, Germany. vollmer@ph-heidelberg.de
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0742-0528 ISBN Medium
Area Expedition Conference
Notes PMID:23130997 Approved no
Call Number LoNNe @ christopher.kyba @ Serial 517
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Author (down) Vollmer, C.; Michel, U.; Randler, C.
Title Outdoor light at night (LAN) is correlated with eveningness in adolescents Type Journal Article
Year 2012 Publication Chronobiology International Abbreviated Journal Chronobiol Int
Volume 29 Issue 4 Pages 502-508
Keywords Adolescent; *Adolescent Behavior/drug effects; Biological Clocks; Central Nervous System Stimulants/administration & dosage; *Circadian Rhythm/drug effects; Computers; Cross-Sectional Studies; Female; Germany; Humans; *Light; Lighting; Male; *Photic Stimulation; *Photoperiod; Questionnaires; *Sleep/drug effects; Television; Time Factors; Video Games; *Wakefulness/drug effects
Abstract External zeitgebers synchronize the human circadian rhythm of sleep and wakefulness. Humans adapt their chronotype to the day-night cycle, the strongest external zeitgeber. The human circadian rhythm shifts to evening-type orientation when daylight is prolonged into the evening and night hours by artificial light sources. Data from a survey of 1507 German adolescents covering questions about chronotype and electronic screen media use combined with nocturnal satellite image data suggest a relationship between chronotype and artificial nocturnal light. Adolescents living in brightly illuminated urban districts had a stronger evening-type orientation than adolescents living in darker and more rural municipalities. This result persisted when controlling for time use of electronic screen media, intake of stimulants, type of school, age, puberty status, time of sunrise, sex, and population density. Time spent on electronic screen media use-a source of indoor light at night-is also correlated with eveningness, as well as intake of stimulants, age, and puberty status, and, to a lesser degree, type of school and time of sunrise. Adequate urban development design and parents limiting adolescents' electronic screen media use in the evening could help to adjust adolescents' zeitgeber to early school schedules when they provide appropriate lighting conditions for daytime and for nighttime.
Address Department of Biology, University of Education Heidelberg, Germany. vollmer@ph-heidelberg.de
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0742-0528 ISBN Medium
Area Expedition Conference
Notes PMID:22214237 Approved no
Call Number IDA @ john @ Serial 150
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