PURPOSE: Circadian rhythms (CR) regulate behavioral and physiological processes, including the sleep-wake cycle. Actigraphy provides objective behavioral data but is influenced by external factors, potentially masking endogenous circadian patterns. Urinary 6-sulfatoxymelatonin (aMT6s) offers a practical marker of endogenous CR in ecological settings. This study examined associations between aMT6s profiles and actigraphy-derived sleep parameters in a clinical population with sleep disturbances.
METHODS: A retrospective analysis was conducted on 69 adult patients assessed in 2023 at the University Hospital of Besançon. Of these, 40 exhibited significant aMT6s rhythmicity and were included in final analyses. Actigraphy data included sleep onset, midpoint, offset, and sleep architecture metrics. aMT6s was collected in 3-hour intervals over 24 h under naturalistic conditions. Cosinor analysis was used to determine aMT6s acrophase, amplitude, and mesor. Pearson correlations were calculated to assess associations between aMT6s and actigraphy measures under both fixed and free sleep schedules.
RESULTS: aMT6s acrophase showed moderate correlations with sleep onset (r = 0.46), midpoint (r = 0.61), and offset (r = 0.63). Stronger correlations were observed under fixed schedules. aMT6s amplitude and mesor demonstrated weaker associations with sleep timing and latency.
CONCLUSION: The moderate, context-dependent correlations underscore that these tools are not redundant but capture distinct aspects of sleep-wake regulation. In a heterogeneous clinical population, this supports a stratified diagnostic approach, using actigraphy as a first-line screening tool and reserving aMT6s assessment for complex cases. This multimodal strategy can refine evaluation and guide personalized chronobiological interventions. Prospective studies are needed to validate the implementation criteria for this stepped-care model in clinical practice.
