Summary
This systematic review of 64 articles identifies rectal body temperature and heart rate as the most reliable objective indicators of light's immediate energizing effect, while ruling out many commonly used measures such as cortisol, skin conductance, and blood pressure. Lighting designers and researchers seeking to validate alerting lighting interventions should prioritize these two physiological endpoints, while noting that study design, time of day, and light brightness significantly influence outcomes.
Key Findings
- Rectal temperature was the best indicator of light's energizing effect: 13 studies showed increases, 6 showed no change, and 1 showed a decrease.
- Heart rate was the second most reliable indicator: 10 studies showed increases, 22 showed no change, and 1 showed a decrease.
- Heart rate and rectal temperature showed concordant changes across 7 mutual studies (trend-level agreement).
- No evidence was found that oxygen consumption, skin conductance, blood pressure, heart rate variability, non-rectal inner temperature, skin temperature, or cortisol could reliably detect light's energizing effect.
- Sympathetic nerve activity (microneurography) showed a noticeable response to light but was assessed in only a single study, limiting conclusions.
- Three moderating factors significantly influenced results: study design quality, whether light was administered during day vs. night, and the relative brightness of the light stimulus.
Categories
The Science of Light: Reviews objective physiological measures of light's immediate energizing effect, analyzing 14 candidate biomarkers across 72 sub-studies.
Sleep & Circadian Health: Examines how light exposure timing (day vs. night) and brightness influence physiological arousal markers relevant to circadian regulation.
Workplace Performance: Findings on light-induced alertness and energizing effects have direct implications for lighting design aimed at maintaining wakefulness and performance.
Author(s)
KV Danilenko
Publication Year
2022
Number of Citations
1
Related Publications
The Science of Light
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Sleep & Circadian Health
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Workplace Performance
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