Bright light exposure before bedtime impairs response inhibition the following morning: a non-randomized crossover study

Chronobiol Int. 2018 Aug;35(8):1035-1044. doi: 10.1080/07420528.2018.1452030. Epub 2018 Mar 26.


Introduction: Bright light exposure in the late evening can affect cognitive function the following morning either by changing the biological clock and/or disturbing sleep, but the evidence for this effect is scarce, and the underlying mechanism remains unknown. In this study, we first aimed to evaluate the effect of bright light exposure before bedtime on frontal lobe activity the following morning using near-infrared spectroscopy (NIRS) during a Go/NoGo task. Second, we aimed to evaluate the effects of bright light exposure before bedtime on polysomnographic measures and on a frontal lobe function test the following morning.

Methods: Twenty healthy, young males (mean age, 25.5 years) were recruited between September 2013 and August 2014. They were first exposed to control light (150 lux) before bedtime (from 20:00 h to 24:00 h) for 2 days and then to bright light (1,000 lux) before bedtime for an additional 5 days. We performed polysomnography (PSG) on the final night of each light exposure period (on nights 2 and night 7) and performed NIRS, which measures the concentrations of oxygenated and deoxygenated hemoglobin (OxyHb and DeoxyHb, respectively), coupled with a Go/NoGo task the following morning (between 09:30 h and 11:30 h). The participants also completed frontal lobe function tests the following morning.

Results: NIRS showed decreased hemodynamic activity (lower OxyHb and a tendency toward higher DeoxyHb concentration) in the right frontal lobe during the NoGo block after 1000-lux light exposure compared with that during the NoGo block after 150-lux light exposure. The commission error rate (ER) during the Go/NoGo task was higher after 1000-lux light exposure than that during the Go/NoGo task after 150-lux light exposure (1.24 ± 1.09 vs. 0.6 ± 0.69, P = 0.002), suggesting a reduced inhibitory response.

Conclusion: This study shows that exposure to bright light before bedtime for 5 days impairs right frontal lobe activation and response inhibition the following morning.

Keywords: Artificial light; NIRS; frontal lobe function; response inhibition.

Publication types

  • Clinical Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activity Cycles / radiation effects*
  • Adult
  • Biomarkers / blood
  • Cerebrovascular Circulation / radiation effects*
  • Circadian Rhythm / radiation effects*
  • Cross-Over Studies
  • Executive Function / radiation effects*
  • Frontal Lobe / blood supply*
  • Frontal Lobe / radiation effects*
  • Hemoglobins / metabolism
  • Humans
  • Light / adverse effects*
  • Male
  • Neuropsychological Tests
  • Oxyhemoglobins / metabolism
  • Polysomnography
  • Reaction Time / radiation effects
  • Sleep / radiation effects*
  • Spectroscopy, Near-Infrared
  • Time Factors
  • Young Adult


  • Biomarkers
  • Hemoglobins
  • Oxyhemoglobins
  • deoxyhemoglobin