Topic: Air pollution and environmental exposures
The short-wavelength content of available light declines steadily through the afternoon, well before nightfall, while the long-wavelength component remains nearly constant. The crossover falls in the late afternoon, at a time set by latitude, geometry and turbidity, within the broad and variably reported onset window of sundowning. We propose that afternoon spectral reddening—rather than darkness itself—is a candidate physical cue for sundowning, possibly mediated by the diminished short-wavelength drive to melanopsin-expressing retinal ganglion cells, whose sensitivity peak lies within the depleted spectral region. The proposal yields testable predictions and implies that lighting interventions should be timed to local solar conditions rather than the clock.
Cite this study APA, Vancouver, BibTeX · download .bib or .ris
APA 7th
Artun, E. C., & Siddiki, A. (2026). Afternoon Spectral Reddening of Daylight as a Candidate Physical Cue for Sundowning Syndrome. Preprints.org. https://doi.org/10.20944/preprints202608.2230.v1
Vancouver
Artun EC, Siddiki A. Afternoon Spectral Reddening of Daylight as a Candidate Physical Cue for Sundowning Syndrome. Preprints.org. 2026. doi:10.20944/preprints202608.2230.v1.
BibTeX
@article{artun2026-9b7a77d6,
author = {Artun, E. C. and Siddiki, A.},
title = {{Afternoon Spectral Reddening of Daylight as a Candidate Physical Cue for Sundowning Syndrome}},
journal = {Preprints.org},
year = {2026},
doi = {10.20944/preprints202608.2230.v1},
url = {https://doi.org/10.20944/preprints202608.2230.v1}
}
Built from the record alzhub holds for this paper, not looked up. Volume, issue and page numbers are not held in the record. Check the citation against the original before you use it.
Key findings
- The short-wavelength content of available light declines steadily through the afternoon, well before nightfall, while the long-wavelength component remains nearly constant.
- The crossover falls in the late afternoon, at a time set by latitude, geometry and turbidity, within the broad and variably reported onset window of sundowning.
- We propose that afternoon spectral reddening—rather than darkness itself—is a candidate physical cue for sundowning, possibly mediated by the diminished short-wavelength drive to melanopsin-expressing retinal ganglion cells, whose sensitivity peak lies within the depleted spectral region.
- The proposal yields testable predictions and implies that lighting interventions should be timed to local solar conditions rather than the clock.
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Study details
- Evidence strengthLow
How this study scored 16/100
Preprint — not yet peer-reviewed. It scored 21 on the same rubric, but non-peer-reviewed sources are capped at 16, so it shows as 16. Scored zero for study design, sample size, effect reported, studied in people and randomized / blinded because the record does not state it. We have no data on times cited, citations per year, impact for its field and year, cited by studies here, still being cited, senior author's track record, institution's track record and multicenter collaboration, so those were left out: it earned 13 of the 62 points we could judge it on, which is 21 out of 100.
| Component | Points | Why |
|---|---|---|
| Journal tier | 2 / 10 | Tier 4 — not a peer-reviewed journal (Preprints.org) |
| Journal's citation record | 0 / 4 | Not a journal article, so the journal's record does not count |
| Study design | 0 / 12 | No study design recorded — scores zero, not guessed (not stated in the record — scored 0) |
| Strength of evidence | 1 / 5 | Rated “low” in our summary |
| Peer-review validation | 4 / 10 | Preprint — not yet peer-reviewed. Hosted on a preprint server. |
| How recent | 5 / 5 | 2026 — within 1 year(s) of the newest study here |
| Sample size | 0 / 4 | Participant count not stated — scores zero (not stated in the record — scored 0) |
| Effect reported | 0 / 3 | No effect size reported — scores zero (not stated in the record — scored 0) |
| Studied in people | 0 / 3 | Not stated whether this was studied in people — scores zero (not stated in the record — scored 0) |
| Randomized / blinded | 0 / 2 | No randomization or blinding stated — scores zero (not stated in the record — scored 0) |
| Times cited | — / 7 | No citation count (not found in OpenAlex) — left out of this score |
| Citations per year | — / 5 | No citation count or no year — left out of this score |
| Impact for its field and year | — / 6 | No field-weighted citation impact (OpenAlex has none yet) — left out of this score |
| Cited by studies here | — / 6 | Not yet checked against this library's citation graph — left out of this score |
| Still being cited | — / 4 | No yearly citation counts — left out of this score |
| Senior author's track record | — / 4 | Senior author's record not available — left out of this score |
| Institution's track record | — / 3 | No institution listed in OpenAlex — left out of this score |
| Multicenter collaboration | — / 3 | Institutions not listed — left out of this score |
| Indexed in PubMed | 1 / 2 | Not in PubMed, but has a DOI |
| Free to read | 0 / 2 | Behind a paywall — scores zero |
| Points | 13 / 62 | Scored on 12 of 20 parts. We have no data for the rest, so they are left out: 13 of the 62 points we could judge it on is 21 out of 100. |
| Total | 21 / 100 | Capped to 16 because this is not a peer-reviewed article. |
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