Improvement in non-24-h sleep-wake rhythm disorder in a sighted individual treated with a melatonin receptor agonist

Non-24-hour sleep-wake rhythm disorder (N24SWD) typically presents in patients with visual impairments that disrupt the ability to entrain to the 24 hour solar cycle. We discuss a 43 year old sighted man who presented with periodic daytime hypersomnia and nighttime insomnia, occasionally leading to <3 hours of sleep per day. Previous polysomnography showed an apnea hypopnea index of 6.2 events per hour. A sleep log of 3 months showed irregular time of sleep onset, and an average of 3 hours of sleep per day. Wrist actigraphy confirmed N24SWD. A trial of tasimelteon 20 mg/day resulting in improved daytime hypersomnia (pre-Epworth Sleepiness Scale (ESS) = 21/24, post-ESS = 5/24; a score of > 10/24 is considered sleepy). Follow-up actigraphy showed marked resolution of phase delay with an average of five hours of sleep. The case demonstrates that tasimelteon is a possible treatment for N24SWD in sighted individuals.