"Too much heat for my non-24-hour sleep-wake disorder!" A case report

The non-24-hour sleep -wake disorder (N24SWD) is a rare condition, sometimes associated with blindness or with suprachiasmatic nuclei lesions, resulting in a free -running rhythm or hypernycthemeral syndrome. Synchronizers, such as light, when light perception remains, melatonin, food intakes, physical activity, social interactions, and temperature, play a key role in the treatment of N24SWD. In this report, we describe a case illustrating the impact of outdoor temperature in a 34 -year -old man with N24SWD effectively treated through a combination of chronotherapy interventions. During 3 consecutive heat waves, he experienced a recurrence of his natural 25.5 -hour free -running rhythm, with a consistent bedtime phase delay caused by temperature, resulting in the discontinuation of chronotherapy. After these heat waves, he was able again to resynchronize his rhythms with the combination of chronotherapeutics. This case report highlights that patients with N24SWD may be particularly at risk of relapse during heat waves, with direct implications for monitoring and reinforcing chronotherapies.