Hypothesis

Consistent evening use of blue‑blocking glasses (450 nm‑filtered lenses) from sunset to bedtime increases nocturnal melatonin sufficient to boost glymphatic cerebrospinal fluid (CSF) influx, thereby reducing brain interstitial waste accumulation and decelerating epigenetic aging metrics in adults aged 40‑60 years.

Mechanistic Rationale

Evening blue light suppresses melatonin via melanopsin‑expressing retinal ganglion cells, shifting circadian phase and diminishing the hormone’s antioxidant and signaling functions2. Melatonin upregulates aquaporin‑4 (AQP4) polarization on astrocytic end‑feet, a key driver of glymphatic CSF‑interstitial fluid exchange7. Enhanced glymphatic flow facilitates clearance of amyloid‑β, tau, and oxidative metabolites that otherwise drive microglial activation and inflammaging6. Reduced interstitial toxin load lowers NF‑κB signaling, curbing age‑related DNA methylation drift at CpG sites associated with the Horvath and Hannum clocks.

Testable Predictions

1. Melatonin Rise: Participants wearing blue‑blocking glasses will show a ≥15 % increase in salivary melatonin AUC (area under the curve) between 20:00 and 02:00 h compared with clear‑lens controls.
2. Glymphatic Boost: Dynamic contrast‑enhanced MRI will reveal a ≥10 % greater CSF influx rate into the cortex during early NREM sleep in the intervention group.
3. Waste Clearance: CSF amyloid‑β42 levels measured by lumbar puncture at 04:00 h will be ↓12 % relative to baseline, while controls show no change.
4. Epigenetic Shift: After 8 weeks, the intervention group’s epigenetic age (DNAmAge) will be ≤0.5 years younger than baseline, whereas controls will exhibit ≥0.2 years increase.
5. Falsifiability: If melatonin elevation occurs without corresponding glymphatic or epigenetic changes, the hypothesis is falsified, indicating melatonin’s role is insufficient to drive the proposed downstream effects.

Experimental Design

• Population: 120 healthy adults, 40‑60 y, stratified by sex and baseline sleep efficiency (>85 %).
• Intervention: Blue‑blocking lenses (≤450 nm transmission <1 %) worn from 30 min before sunset until lights out; control group wears identical frames with clear lenses.
• Duration: 8 weeks of nightly use, with compliance logged via smartphone ambient light sensors.
• Outcomes:
  • Salivary melatonin every 30 min from 19:00‑03:00 h (LC‑MS/MS).
  • Glymphatic MRI using intrathecal gadobutrol contrast and kinetic modeling.
  • CSF amyloid‑β42, total tau, phospho‑tau (ELISA).
  • Blood‑based inflammatory markers (IL‑6, TNF‑α, CRP).
  • Epigenetic clock assessment from peripheral blood mononuclear cells (Illumina EPIC array).
• Analysis: Mixed‑effects models adjusting for age, sex, BMI, and baseline values; intention‑to‑treat primary analysis.

Expected Impact

Confirming this hypothesis would link a simple, low‑cost behavioral tweak to a measurable slowing of biological aging, providing a mechanistic bridge between circadian hygiene, cerebrovascular health, and longevity. Failure to observe the predicted glymphatic or epigenetic improvements would refine our understanding of melatonin’s pleiotropic actions and guide future interventions targeting specific downstream pathways.