Proceedings of the National Academy of Sciences of the United States of America

Strong but varying effects of evening light on the human body clock

Updated

Abstract

The group-level for 50% is 24.60 lux, indicating high sensitivity to evening light.

  • Interindividual differences in sensitivity to evening light may contribute to vulnerability to circadian disruption.
  • Light intensities of 10, 30, and 50 lux led to later melatonin onset by 22, 77, and 109 minutes, respectively.
  • Individual effective dose values varied significantly, ranging from 6 lux in the most sensitive individual to 350 lux in the least sensitive.
  • A 26% coefficient of variation in individual effective doses suggests substantial variability in response to light exposure.
  • The findings imply that the same light environment can affect individuals' circadian systems differently.

Simplified

Key numbers

24.60
Group-Level for
for 50% in the group.
6 of 350
Range of Individual Values
Individual effective doses ranged widely.
109 min
Delay in Onset
Apparent onset at 50 was delayed by this duration.

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Funding

Competing interests

Conflict of interest statement: C.A. has received a research award/prize from Sanofi-Aventis; contract research support from VicRoads, Rio Tinto Coal Australia, National Transport Commission, and Tontine/Pacific Brands; lecturing fees from Brown Medical School/Rhode Island Hospital, Ausmed, Healthmed, and TEVA Pharmaceuticals; and reimbursements for conference travel expenses from Philips Healthcare. C.A. has served as a consultant to the Rail, Bus, and Tram Union; the Transport Accident Commission; the National Transportation Committee; and Melius Consulting. C.A. has also served as an expert witness and/or consultant in relation to fatigue and drowsy driving. C.A. is a Theme Leader in the Cooperative Research Centre for Alertness, Safety, and Productivity. S.M.W.R. has served as a consultant through his institution to Vanda Pharmaceuticals, Philips Respironics, and Teva Pharma Australia and has, through his institution, received research grants and/or unrestricted educational grants from Vanda Pharmaceuticals, Takeda Pharmaceuticals North America, Philips Lighting, Philips Respironics, Cephalon, and ResMed Foundation, as well as reimbursements for conference travel expenses from Vanda Pharmaceuticals. S.M.W.R. serves as a Program Leader and consultant to the Cooperative Research Centre for Alertness, Safety, and Productivity. S.W.L. has had a number of commercial interests in the last 36 mo (2016–2019). None are directly related to the research reported in this paper but, in the interests of full disclosure, are outlined as follows. S.W.L. has received consulting fees from the Atlanta Falcons, Atlanta Hawks, BHP Billiton, Noble Insights, Slingshot Insights, and Team C Racing; honoraria and/or paid travel from BHP Billiton, DIN, Emory University, IES, Ineos, SLTBR, Solemma, and Teague; has current consulting contracts with Akili Interactive, Apex 2100 Ltd., Consumer Sleep Solutions, Headwaters Inc., Hintsa Performance AG, Light Cognitive, Lighting Science Group Corporation, Mental Workout, PlanLED, Six Senses, Stantec, and Wyle Integrated Science and Engineering; has received unrestricted equipment gifts from Bionetics Corporation and F. Lux Software LLC and royalties from Oxford University Press; and has served as a paid expert in legal proceedings related to light, sleep, and health. He holds a patent through Harvard University and Brigham and Women’s Hospital for “Systems and Methods for Determining and/or Controlling Sleep Quality.”
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