Hypothesis

Combining a brief morning bright‑light pulse (≥30 min of ~5000 lux within 15 min of waking) with evening use of blue‑light filtering lenses that attenuate 460‑480 nm wavelengths by >50 % will produce a synergistic advance of the circadian phase and a reduction in sleep onset latency of at least 30 minutes in individuals homozygous for the PER3^5/5 allele, whereas the same intervention will produce a smaller (<10 min) or no effect in PER3^4/4 homozygotes.

Rationale

• Morning bright light drives ipRGC‑mediated phase advances via the retinohypothalamic tract, with the first 30 minutes delivering ~75 % of the effect of a 2‑hour exposure Morning bright light advances circadian rhythms and shifts melatonin onset earlier.
• Evening blue light suppresses melatonin through melanopsin peaks at ~480 nm; filtering this band reduces melatonin suppression and sleep onset latency Evening light delays clocks and suppresses melatonin.
• PER3^5/5 carriers exhibit heightened circadian light sensitivity and larger melatonin amplitude shifts compared with PER3^4/4 carriers, a trait linked to altered ipRGC signaling kinetics.
• Therefore, advancing the phase with morning light while preserving melatonin onset with evening blue‑light blockade should compound the phase‑advancing effect specifically in PER3^5/5 individuals, shortening the interval between dim‑light melatonin onset (DLMO) and bedtime.

Predictions

1. In a within‑subject crossover trial, PER3^5/5 participants will show a mean advance of DLMO of ≥45 min and a reduction in sleep onset latency of ≥30 min under the combined intervention relative to a dim‑light control.
2. PER3^4/4 participants will exhibit ≤15 min DLMO advance and ≤10 min latency reduction under the same conditions.
3. The magnitude of latency reduction will correlate positively with individual ipRGC‑mediated pupil constriction response to 480 nm light measured before intervention.

Experimental Design

• Recruit 30 healthy adults stratified by PER3 genotype (15 5/5, 15 4/4).
• Each participant completes two 7‑day conditions in random order: (a) combined intervention (morning 5000 lux light box 30 min within 15 min of waking + evening blue‑light blocking glasses 2 h before bedtime) and (b) sham control (dim red light <50 lux morning; clear lenses evening).
• Collect saliva every 30 min from 18:00–22:00 to assay melatonin and compute DLMO.
• Use wrist actigraphy and sleep‑diaries to derive sleep onset latency.
• Measure pupil constriction to a 480 nm stimulus at baseline to quantify ipRGC sensitivity.

Falsifiability

If the combined intervention fails to produce a statistically significant interaction between genotype and condition on DLMO advance or sleep onset latency (p > 0.05), the hypothesis is falsified. Similarly, if PER3^5/5 individuals do not show a greater latency reduction than PER3^4/4 individuals, or if the effect does not correlate with ipRGC sensitivity, the mechanistic claim that PER3‑dependent ipRGC signaling mediates the synergy is unsupported.

Potential Confounds and Mitigation

• Variability in habitual light exposure: enforce a standardized light‑dark diary and restrict caffeine/alcohol.
• Placebo effect of glasses: use indistinguishable clear lenses in control.
• Seasonal photoperiod: conduct study within the same month to control for natural daylight duration.

By testing whether genotype‑specific ipRGC signaling determines the efficacy of combined morning advances and evening melatonin preservation, this hypothesis bridges the observed power of timed light, the mechanistic gap in evening blue‑light quantification, and the emerging push for personalized, wearable‑guided sleep interventions.