Circadian-informed lighting produced a mean 5.6 hours greater delay in core body temperature timing compared to standard lighting after simulated night shifts.
Significant interactions were observed between lighting conditions and the timing of core body temperature and melatonin onset delays.
Circadian-informed lighting resulted in a 4.2-hour greater delay in melatonin onset timing compared to standard lighting.
The study involved 19 healthy participants, with assessments conducted over two separate 8-day visits.
Lighting conditions were tested under simulated night work to evaluate their effects on circadian adjustment.
Simplified
STUDY OBJECTIVE: Night work has detrimental impacts on sleep and performance, primarily due to misalignment between sleep-wake schedules and underlying circadian rhythms. This study tested whether circadian-informed lighting accelerated circadian phase delay, and thus adjustment to night work, compared to blue-depleted standard lighting under simulated submariner work conditions.
METHODS: Nineteen healthy sleepers (12 males; mean ± SD aged 29 ± 10 years) participated in two separate 8-day visits approximately 1 month apart to receive, in random order, circadian-informed lighting (blue-enriched and dim, blue-depleted lighting at specific times) and standard lighting (dim, blue-depleted lighting). After an adaptation night (day 1), salivary (DLMO) assessment was undertaken from 18:00 to 02:00 on days 2-3. During days 3-7, participants completed simulated night work from 00:00 to 08:00 and a sleep period from 10:00 to 19:00. Post-condition DLMO assessment occurred from 21:00 to 13:00 on days 7-8. Ingestible capsules continuously sampled temperature to estimate daily (Tmin) time. Tmin and DLMO circadian delays were compared between conditions using mixed effects models.
RESULTS: There were significant condition-by-day interactions in Tmin and DLMO delays (both p < .001). After four simulated night shifts, circadian-informed lighting produced a mean [95% CI] 5.6 [3.0 to 8.2] hours greater delay in Tmin timing and a 4.2 [3.0 to 5.5] hours greater delay in DLMO timing compared to standard lighting.
CONCLUSIONS: Circadian-informed lighting accelerates adjustment to shiftwork in a simulated submariner work environment. Circadian lighting interventions warrant consideration in any dimly lit and blue-depleted work environments where circadian adjustment is relevant to help enhance human performance, safety, and health.
Key numbers
4.2 hours
Timing Delay Increase
Circadian-informed lighting vs. standard lighting after four night shifts.
5.6 hours
Delay Increase
Circadian-informed lighting vs. standard lighting after four night shifts.
19 of 24
Participant Completion
Total participants initially planned for the study.
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