Indoor Lighting Spectra vs Circadian Gene Expression
Indoor lighting is admissible as biologically neutral only if commonly used spectra do not measurably alter circadian gene expression under controlled exposure conditions.
An environmental condition is admissible only if it does not measurably alter core biological signaling pathways under ordinary exposure. If gene expression shifts occur, neutrality is structurally invalid.
Indoor lighting is biologically neutral over short exposure
The assumption under test is that common indoor lighting spectra do not significantly alter circadian gene expression during short, controlled exposures.
Lighting is treated as non-biological infrastructure
Indoor lighting is designed, deployed, and regulated primarily for visibility and efficiency, not for biological interaction.
Buildings, workplaces, and homes assume lighting is functionally inert with respect to human biology at typical exposure levels.
Human cells exposed to controlled light spectra
- Cell type: human fibroblasts (synchronized)
- Exposure: 4 hours continuous illumination
- Environment: 37 °C, 5% CO₂
- Intensity: ~100 lux at cell layer
Spectral comparison under controlled conditions
- Blue-enriched LED (~460 nm peak)
- Warm white LED (~3000 K)
- Cool white LED (~6500 K)
- Dark control (no light exposure)
Exposure begins immediately after circadian synchronization to isolate light as the governing variable.
Circadian gene expression shift relative to dark control
The governing variable is the fold-change in expression of core circadian genes (PER2, BMAL1) relative to dark control conditions.
Absolute expression is not the signal—deviation from baseline is.
Direct molecular readout
- RNA extraction immediately after exposure
- qPCR for PER2, BMAL1
- Normalization to GAPDH
- ΔΔCt analysis relative to dark control
PASS
Both PER2 and BMAL1 remain within ±1.5-fold of dark control.
FAIL
Any gene shifts ≥1.5-fold relative to dark control.
What failure means
Failure indicates that indoor lighting is not biologically neutral at the cellular level, even under short exposure conditions.
The environment is not passive—it is actively interacting with biological timing systems.
What this does not claim
- No behavioral or sleep conclusions
- No clinical or health claims
- No extrapolation to whole organisms
This test isolates molecular response only.
Neutral environments do not move core biological signals.
If lighting shifts circadian gene expression, it is not passive infrastructure—it is an active biological input.