title: The impact of morning light intensity and environmental temperature on body temperatures and alertness.
abstract: Indoor temperature and light exposure are known to affect body temperature, productivity and alertness of building occupants. However, not much is known about the interaction between light and temperature exposure and the relationship between morning light induced alertness and its effect on body temperature. Light intensity and room temperature during morning office hours were investigated under strictly controlled conditions. In a randomized crossover study, two white light conditions (4000K, either bright 1200lx or dim 5lx) under three different room temperatures (26, 29 and 32°C) were investigated. A lower room temperature increased the core body temperature (CBT) and lowered skin temperature and the distal-proximal temperature gradient (DPG). Moreover, a lower room temperature reduced the subjective sleepiness and reaction time on an auditory psychomotor vigilance task (PVT), irrespective of the light condition. Interestingly, the morning bright light exposure did affect thermophysiological parameters, i.e. it decreased plasma cortisol, CBT and proximal skin temperature and increased the DPG, irrespective of the room temperature. During the bright light session, subjective sleepiness decreased irrespective of the room temperature. However, the change in sleepiness due to the light exposure was not related to these physiological changes.
authors.affiliation: Department of Human Biology & Movement Sciences, NUTRIM, Maastricht University, Maastricht, The Netherlands. Electronic address: m.tekulve@maastrichtuniversity.nl.
authors.forename: Marije
authors.initials: M
authors.lastname: Te Kulve
authors.affiliation: Philips Lighting Research, Eindhoven, The Netherlands.
authors.forename: Luc J M
authors.initials: LJM
authors.lastname: Schlangen
authors.affiliation: Department of Human Biology & Movement Sciences, NUTRIM, Maastricht University, Maastricht, The Netherlands; School of Built Environment and Infrastructure, Avans University of Applied Sciences, Tilburg, The Netherlands.
authors.forename: Lisje
authors.initials: L
authors.lastname: Schellen
authors.affiliation: Department of Mechanical Engineering, Eindhoven University of Technology, The Netherlands.
authors.forename: Arjan J H
authors.initials: AJH
authors.lastname: Frijns
authors.affiliation: Department of Human Biology & Movement Sciences, NUTRIM, Maastricht University, Maastricht, The Netherlands.
authors.forename: Wouter D
authors.initials: WD
authors.lastname: van Marken Lichtenbelt
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D001288:Attention / Q000502:physiology*; D001831:Body Temperature / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008027:Light; D008550:Melatonin / Q000378:metabolism; D011597:Psychomotor Performance / Q000502:physiology*; D012890:Sleep / Q000502:physiology; D013696:Temperature; D055815:Young Adult
chemical_list: D008550:Melatonin
keywords: Alertness; Light; Productivity; Sleepiness; Thermophysiology