ED Sciences de la Vie et de la Santé
Digital phenotyping for an evaluative and interventional approach of sleep in the general and clinical population
by Julien COELHO (Sommeil, Addiction et Neuropsychiatrie)
The defense will take place at 14h30 - Broca 146 rue Léo Saignat
in front of the jury composed of
- Pierre PHILIP - Professeur - Université de Bordeaux - Directeur de these
- CHARLES MORIN - Professeur - Université de Laval - Rapporteur
- LAURE PETER-DEREX - Professeure des universités - praticienne hospitalière - Université Lyon 1 - Rapporteur
- XAVIER DROUOT - Professeur des universités - praticien hospitalier - Université de Poitiers - Examinateur
- MARIE-PIA D'ORTHO - Professeure des universités - Université Neurodiderot - Examinateur
Sleep, when approached from the perspective of sleep health, represents a key target for interventions aiming to evaluate and promote both physical and mental health in the general population. The amount of sleep and homeostatic pressure have been historically well studied, but more recently, circadian rhythms and their physiology have been brought back to the forefront of sleep health. These rhythms can be described along six dimensions: circadian phase, amplitude, and stability; nychthemeral timing and regularity; and sleep complaints of circadian origin. These dimensions help characterize two main types of circadian disruptions: those due to circadian misalignment (i.e., a discrepancy between nychthemeral timing and circadian phase, not compensated by sufficient amplitude or stability, and resulting in sleep complaints), and those due to a dysfunction of the biological clock (i.e., intrinsic circadian physiology alterations causing pronounced nychthemeral irregularity and associated sleep complaints). Such disruptions are particularly common in psychiatric disorders and represent an important therapeutic target to improve mental health. Digital tools present both challenges and opportunities for the assessment and promotion of circadian physiology. This theoretical framework has guided a three-pronged research approach. First, we focused on improving the measurement tools for circadian rhythms. We analyzed 14 existing questionnaires assessing circadian rhythms to examine their content, assess their homogeneity, and identify their most appropriate use. This analysis highlighted the importance of the MCTQ (Munich ChronoType Questionnaire), which we translated and validated in French, thereby providing the first French-language tool for assessing circadian misalignment. The next step is to validate a French version of the SRQ (Sleep Regularity Questionnaire) and to develop a new, holistic circadian questionnaire. Second, we sought to better characterize the relationship between circadian physiology and sleep health. We found a strong association between nychthemeral sleep behaviors (specifically sleep timing and sleep regularity) and mental health, independent of other dimensions of sleep health and consistent over time. Given the complexity of interactions among the different dimensions of circadian physiology, further investigation will require both experimental protocols and large-scale observational cohorts. Finally, we explored how digital tools can be used to optimize circadian physiology and promote sleep health. We showed that in the context of a personalized behavioral intervention delivered by an autonomous conversational agent, improvements in nychthemeral sleep regularity predicted improvements in mental health. Circadian rhythms, therefore, represent a promising target for mental health promotion. However, these tools still need to be refined and validated in clinical populations. Ideally, they should also incorporate additional dimensions of circadian physiology not addressed here, such as sensitivity to and exposure to zeitgebers (external synchronizing cues). Furthermore, consideration of social and environmental determinants, alongside individual factors, is essential for accurate characterization and optimal efficacy of circadian-targeted interventions. Greater integration of interactions with homeostatic sleep pressure is also needed. Defining circadian health, developing a corresponding questionnaire, and proposing specific biomarkers are all important future directions. Moreover, studying circadian rhythms in the context of a 24/7 society raises ethical questions that should not be overlooked. In conclusion, circadian physiology is a key determinant of both sleep and overall health. It constitutes a priority target for addressing the public health challenge posed by sleep disturbances.