Impact of ipRGC-influenced lighting metrics on sleep, alertness and mood in university students: A field study using wearable sensors

What the study found

Fifty students wore spectral light sensors for a week while logging alertness, mood and sleep. Melanopic light in the preceding 30 minutes to 3 hours was weakly linked to higher alertness (r about 0.18), and more light in the 3 hours before bed was linked to worse sleep quality (r = -0.22) and later sleep onset. Students met WELL and Brown et al. daytime thresholds only 17 to 32% of the time, and meeting those thresholds was not linked to sleep.

Limitations

Correlational, small effects, a student sample and self-reported sleep; it cannot show that meeting light recommendations would change outcomes.

Neurodesign interpretation

Evening light and recent daytime light both seem to matter, but this gives no direct support for threshold-based compliance metrics as a design target.

Possible design implications

Hypothesis: limiting bright light in the hours before bed may matter more for sleep than meeting daytime melanopic thresholds; needs intervention studies.

Study design

Observational field study (wearable sensors)

Population

University students aged 20 to 31, Toronto, Canada; no diagnosed sleep disorders. Sample: 50 (56 recruited).

Setting

Field: everyday environments over one week per person (fall and winter, 2023 to 2025)

Field

Lighting + circadian, Sleep science

Mechanism

ipRGC / melanopsin response, Circadian phase response

Spatial variable

Light level, Light timing

Keywords

light level, light timing, iprgc / melanopsin response, circadian phase response

Notes and follow-up

Related records: ND-0100, ND-0104, ND-0037, ND-0039, ND-0040, ND-0038. Publisher and Crossref records give author initials only.