Claude Gronfier

Biography

Claude Gronfier is a neurobiologist specializing in biological rhythms and sleep. After completing a PhD in neuroscience at the University of Strasbourg, he joined Chuck Czeisler at Harvard Medical School to study the impact of spaceflight on biological rhythms. His research at the Lyon Neuroscience Research Center of the French National Institute for Health and Medical Research (Inserm) focuses on the mechanisms involved in synchronizing the circadian clock, the effects of nocturnal light, and the development of photic strategies for the treatment of shift work disorders, jet lag, mood and certain pathologies. Claude Gronfier is vice-president of the Société́ francophone de chronobiologie and a member of the scientific council of the Société́ de physiologie. He chaired́ the recent report by the Agence nationale de sécurité sanitaire de l’alimentation, de l’environnement et du travail (Anses) on Les effets sanitaires du travail de nuit (2016). He is co-author of several books and chapters in scientific and general public works (Les mécanismes du sommeil, Le Pommier, 2013, En finir avec le blues de l’hiver, Marabout, 2014), expert reports and consultations for the Ministry of Health and the Ministry of Labor, the Haute autorité́ de santé, and is author of over 60 scientific articles in international journals.

Conference: Should we sleep at night and see the light during the day?

24-hour rhythms are observed in most species, from unicellulars to humans. Sleep, cognitive performance, hormone secretions, body temperature, cell division and DNA repair are all under the control of a circadian biological clock (which governs rhythms close to 24 hours). The study of these rhythms is called chronobiology, and its three pioneers were awarded the Nobel Prize in Medicine and Physiology in 2017. Light is the most powerful synchronizer of the biological clock to the 24-hour day, so light hygiene is crucial. In unsuitable light conditions, there is a deficit in the synchronization of the circadian clock, which generally results in the alteration of numerous functions (hormones, core temperature, cardiovascular system, immunological system), the degradation of neurocognitive processes (cognitive performance, memory) and the disruption of sleep and vigilance. Night work, and the delayed onset of sleep observed particularly in adolescents and young adults, are the most frequent situations of circadian desynchronization. They can severely affect health.