1183 Chasing Sleep: Circadian Rhythm Sleep Disorder - Free-Running Type

Introduction Circadian rhythm sleep disorder, free-running type (CRSD-FRT) is a disorder caused by a circadian pacemaker that is out of sync with the 24-hour light-dark cycle. CRSD-FRT is rare in sighted persons but prevalent in totally blind individuals. In sighted people, CRSD-FRT can be associated with psychiatric conditions such as depression, but the etiology remains unknown. It is postulated that sighted persons may have reduced light sensitivity for phase-resetting effects. Symptoms of CRSD-FRT include insomnia, excessive daytime sleepiness and functional impairment. Here we present a unique case of CRSD-FRT in a sighted female with a history of depression. Report of case(s) A 27-year-old sighted female with history of depression previously treated with an SSRI presented to the sleep clinic with a chief complaint of chronic insomnia. Historically, she went to bed at 3 A.M. and awoke at 2 P.M. Sleep onset latency was normal. Estimated total sleep time was 10 hours. She denied history of any other sleep disorders. She experienced a similar delayed sleep routine as a teenager and assumed it was due to late-night gaming. She tried multiple sleep aids including trazodone, melatonin, and diphenhydramine, unsuccessfully. She described a “normal” sleeping schedule once per month, but then her sleep schedule began to move later and later, until it was normal again. She worked from home and was self-employed, giving her flexibility over her schedule. Her Epworth Sleepiness Score was 13 at the initial visit. Interestingly, her sibling had a similar sleeping pattern. Actigraphy was done which confirmed patient’s diagnosis of CRSD-FRT. She was advised to start Tasimelteon. Conclusion The patient was previously misdiagnosed with insomnia. CRSD-FRT is rare in sighted persons and may be underdiagnosed. Our patient’s CRSD-FRT may be linked to her history of depression and SSRI use. According to one study, a clinical dose of SSRI resulted in 47% increase in melatonin suppression, which increases the human circadian system’s responsiveness to light. Her flexible work from home schedule may also be a contributing factor. When changing or eliminating social time cues could precipitate the development of CRSD-FRT due to variations in the length of circadian rhythm. Support (if any)