Sighted non-24-hour sleep-wake disorder is a heterogeneous condition caused by distinct dysfunctions in the circadian photic entrainment pathway
This multimodal phenotyping of two sighted N24SWD patients revealed two distinct pathophysiological mechanisms: one patient had preserved melanopsin function but absent light-induced melatonin suppression and a markedly prolonged intrinsic period (~25 h), while the other had impaired melanopsin response (reduced PIPR) but retained melatonin suppression and a period within the upper physiological range (24.20 h). These findings indicate that N24SWD in sighted individuals is not a unitary disorder but results from dysfunction at different levels of the circadian photic entrainment pathway.
This article is automatically generated from the structured evidence profile behind the claim above. Scores reflect the quality and quantity of available research, not clinical advice.
Sighted non-24-hour sleep-wake disorder is a heterogeneous condition caused by distinct dysfunctions in the circadian photic entrainment pathway The current body of evidence comprises 1 study. EvidenceHub rates the overall confidence at 32/100 (low).
The Claim
Sighted non-24-hour sleep-wake disorder is a heterogeneous condition caused by distinct dysfunctions in the circadian photic entrainment pathway
This conclusion is most relevant to: Two sighted patients with confirmed non-24-hour sleep-wake disorder.
What the Research Shows
The conclusion draws on 1 linked study. Highlights from the cited literature:
- ▸Multimodal circadian phenotyping reveals distinct mechanisms of photic entrainment failure in two sighted patients with non-24-hour sleep-wake disorder. (Sleep medicine, 2026) —
How It Works
The proposed biological pathway:
- ▸Patient 1: Normal melanopsin response (normal PIPR), but no melatonin suppression regardless of light timing or illuminance
- ▸Patient 1: Intrinsic circadian period markedly prolonged (~25 h)
- ▸Patient 2: Impaired melanopsin response (reduced PIPR), but melatonin suppression retained across all light conditions
- ▸Patient 2: Intrinsic period within upper physiological range (24.20 h)
- ▸Result: Distinct pathophysiological mechanisms underlie failure of photic entrainment in sighted N24SWD
Who Might Benefit
Evidence fit by population:
- ▸Two sighted patients with confirmed non-24-hour sleep-wake disorder
Recommended Dose
N/A
Limitations & Caveats
Important context when interpreting this evidence:
- ▸Only two patients were studied, limiting generalizability
- ▸No control group for comparison
- ▸The study is descriptive and does not establish causality
- ▸The light exposure protocol was limited to three 15-min exposures, which may not capture full circadian light responsiveness
Frequently Asked Questions
What is non-24-hour sleep-wake disorder (N24SWD)?▼
N24SWD is a rare circadian rhythm disorder where the internal body clock is not aligned with the 24-hour day, leading to progressive delays in sleep-wake timing. It is most common in blind individuals but can occur in sighted people.
What are the two distinct mechanisms of photic entrainment failure identified in this study?▼
The first mechanism involves a normal melanopsin response but a failure of light to suppress melatonin, combined with a very long intrinsic period (~25 h). The second mechanism involves impaired melanopsin function (reduced PIPR) but preserved melatonin suppression, with a period in the upper normal range (24.20 h).
How was circadian light responsiveness measured?▼
Circadian light responsiveness was evaluated using three 15-minute light exposures at different irradiance levels and circadian phases across three consecutive nights, with simultaneous measurement of light-induced melatonin suppression.
What is the clinical implication of this study?▼
The findings suggest that sighted N24SWD is heterogeneous, and mechanistic phenotyping could guide personalized treatment targeting the specific impaired component of the circadian system, such as melanopsin function or light responsiveness.
References
- 1.Kilic Huck Ü, Vasseur F, Braun Hughes S, Morris F, Comtet H, Hugueny L, Reix N, Geoffroy PA, Bourgin P. “Multimodal circadian phenotyping reveals distinct mechanisms of photic entrainment failure in two sighted patients with non-24-hour sleep-wake disorder..” Sleep medicine, 2026. PMID: 42612567 DOI: 10.1016/j.sleep.2026.109204