Moderate, context-dependent correlations between urinary 6-sulfatoxymelatonin acrophase and actigraphy-derived sleep timing underscore that these tools capture distinct aspects of sleep-wake regulation and support a stratified diagnostic approach in clinical populations with sleep disorders.
Key Findings
Results
aMT6s acrophase showed moderate correlations with actigraphy-derived sleep timing measures in patients with sleep disturbances.
Pearson correlations were calculated between aMT6s acrophase and actigraphy sleep parameters.
Correlation with sleep onset: r = 0.46.
Correlation with sleep midpoint: r = 0.61.
Correlation with sleep offset: r = 0.63.
These were described as 'moderate correlations,' indicating a meaningful but incomplete relationship between endogenous circadian phase and behavioral sleep timing.
Results
Stronger correlations between aMT6s acrophase and actigraphy measures were observed under fixed sleep schedules compared to free sleep schedules.
Analyses were conducted separately under fixed and free sleep schedule conditions.
Fixed schedules yielded stronger correlations than free schedules, suggesting that external sleep constraints reduce variability and improve alignment between endogenous and behavioral measures.
This context-dependency indicates that free-living conditions may introduce behavioral factors that mask endogenous circadian patterns.
Results
aMT6s amplitude and mesor demonstrated weaker associations with sleep timing and latency compared to acrophase.
Cosinor analysis was used to derive aMT6s acrophase, amplitude, and mesor from 3-hour urine samples collected over 24 hours.
Amplitude and mesor showed weaker correlations with actigraphy sleep parameters than acrophase.
These parameters were also assessed for associations with sleep latency.
The weaker associations suggest that the timing (acrophase) of melatonin secretion is more closely linked to behavioral sleep timing than the magnitude or average level of secretion.
Methods
Of 69 adult patients assessed, only 40 exhibited significant aMT6s rhythmicity and were included in final analyses.
This was a retrospective observational study conducted at the University Hospital of Besançon in 2023.
69 adult patients with sleep disturbances were initially assessed.
29 patients (approximately 42%) were excluded from final analyses due to absence of significant aMT6s rhythmicity.
aMT6s was collected in 3-hour intervals over 24 hours under naturalistic (ecological) conditions.
Cosinor analysis was used to determine rhythmicity and compute circadian parameters.
Discussion
The study supports a stratified diagnostic approach using actigraphy as a first-line screening tool and reserving aMT6s assessment for complex cases.
The authors conclude that actigraphy and aMT6s 'are not redundant but capture distinct aspects of sleep-wake regulation.'
Actigraphy provides objective behavioral data but is influenced by external factors that may mask endogenous circadian patterns.
Urinary aMT6s is described as 'a practical marker of endogenous CR in ecological settings.'
The authors propose a 'multimodal strategy' to 'refine evaluation and guide personalized chronobiological interventions.'
Prospective studies are identified as needed to validate the implementation criteria for this 'stepped-care model' in clinical practice.
Methods
The study population was heterogeneous, consisting of adult clinical patients with sleep disturbances assessed in a real-world hospital setting.
The study was conducted at a university hospital (CHU Besançon) in 2023.
The retrospective design relied on existing clinical data rather than controlled experimental conditions.
Patients were assessed under naturalistic conditions, reflecting ecological validity but introducing potential confounders.
Heterogeneity of the clinical population is cited as a factor affecting correlation strength and generalizability.
What This Means
This research suggests that there is a moderate but meaningful relationship between the timing of melatonin secretion (measured through urine) and when people with sleep disorders actually fall asleep, reach the midpoint of sleep, and wake up. Melatonin is a hormone that helps regulate the body's internal clock, and measuring it in urine over 24 hours gives insight into a person's biological sleep rhythm. The study found that the peak timing of melatonin (called the acrophase) was a better predictor of sleep timing than the amount of melatonin produced, and that this relationship was stronger when people followed a fixed sleep schedule rather than sleeping whenever they wanted.
Importantly, the research also found that nearly 42% of patients did not show a clear melatonin rhythm at all, meaning the urine test was not useful for everyone. This suggests that melatonin testing works best as a targeted tool rather than a routine test for all patients with sleep problems. The researchers propose that standard wrist-worn activity monitors (actigraphy) should be used first to assess sleep behaviors, with urine melatonin testing reserved for more complex cases where understanding the biological clock is essential.
This research matters because it suggests a smarter, two-step approach to diagnosing sleep disorders: start with widely available wearable devices, and add hormone testing only when needed. This could help clinicians better tailor treatments — such as light therapy or melatonin supplementation — to an individual's specific biological clock, rather than relying on behavioral data alone. Future prospective studies are needed to confirm when and for whom this combined approach is most beneficial.
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Galli S, Poirson B, Bourdin H, Haffen E, Giustiniani J. (2026). Correlation between urinary 6-sulfatoxymelatonin and actigraphy data in a clinical population with sleep disorders: an observational study.. Sleep & breathing = Schlaf & Atmung. https://doi.org/10.1007/s11325-026-03706-y