title: Non-24-Hour Sleep-Wake Disorder Revisited - A Case Study.
abstract: The human sleep-wake cycle is governed by two major factors: a homeostatic hourglass process (process S), which rises linearly during the day, and a circadian process C, which determines the timing of sleep in a ~24-h rhythm in accordance to the external light-dark (LD) cycle. While both individual processes are fairly well characterized, the exact nature of their interaction remains unclear. The circadian rhythm is generated by the suprachiasmatic nucleus ("master clock") of the anterior hypothalamus, through cell-autonomous feedback loops of DNA transcription and translation. While the phase length (tau) of the cycle is relatively stable and genetically determined, the phase of the clock is reset by external stimuli ("zeitgebers"), the most important being the LD cycle. Misalignments of the internal rhythm with the LD cycle can lead to various somatic complaints and to the development of circadian rhythm sleep disorders (CRSD). Non-24-hour sleep-wake disorders (N24HSWD) is a CRSD affecting up to 50% of totally blind patients and characterized by the inability to maintain a stable entrainment of the typically long circadian rhythm (tau > 24.5 h) to the LD cycle. The disease is rare in sighted individuals and the pathophysiology less well understood. Here, we present the case of a 40-year-old sighted male, who developed a misalignment of the internal clock with the external LD cycle following the treatment for Hodgkin's lymphoma (ABVD regimen, four cycles and AVD regimen, four cycles). A thorough clinical assessment, including actigraphy, melatonin profiles and polysomnography led to the diagnosis of non-24-hour sleep-wake disorders (N24HSWD) with a free-running rhythm of tau = 25.27 h. A therapeutic intervention with bright light therapy (30 min, 10,000 lux) in the morning and melatonin administration (0.5-0.75 mg) in the evening failed to entrain the free-running rhythm, although a longer treatment duration and more intense therapy might have been successful. The sudden onset and close timely connection led us to hypothesize that the chemotherapy might have caused a mutation of the molecular clock components leading to the observed elongation of the circadian period.
authors.affiliation: Centre for Chronobiology, Psychiatric Hospital of the University of Basel, Basel, Switzerland; Transfaculty Research Platform Molecular and Cognitive Neurosciences, University of Basel, Basel, Switzerland.
authors.forename: Corrado
authors.initials: C
authors.lastname: Garbazza
authors.affiliation: Sleep-Wake-Epilepsy-Centre, Department of Neurology, Inselspital, Bern University Hospital , Bern , Switzerland.
authors.forename: Vivien
authors.initials: V
authors.lastname: Bromundt
authors.affiliation: Transfaculty Research Platform Molecular and Cognitive Neurosciences, University of Basel, Basel, Switzerland; Neurobiology Laboratory for Brain Aging and Mental Health, Psychiatric Hospital of the University of Basel, Basel, Switzerland.
authors.forename: Anne
authors.initials: A
authors.lastname: Eckert
authors.affiliation: Center for Sleep Medicine, Hirslanden Clinic Zurich , Zurich , Switzerland.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Brunner
authors.affiliation: Transfaculty Research Platform Molecular and Cognitive Neurosciences, University of Basel, Basel, Switzerland; Neurobiology Laboratory for Brain Aging and Mental Health, Psychiatric Hospital of the University of Basel, Basel, Switzerland.
authors.forename: Fides
authors.initials: F
authors.lastname: Meier
authors.affiliation: Charité - Universitaetsmedizin Berlin , Berlin , Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Hackethal
authors.affiliation: Centre for Chronobiology, Psychiatric Hospital of the University of Basel, Basel, Switzerland; Transfaculty Research Platform Molecular and Cognitive Neurosciences, University of Basel, Basel, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Cajochen
keywords: Hodgkin’s lymphoma; bright light therapy; circadian rhythm sleep disorders; melatonin; non-24-hour sleep-wake disorder