NON-24-HOUR SLEEP-WAKE SYNDROME IN A SIGHTED MAN - CIRCADIAN-RHYTHM STUDIES AND EFFICACY OF MELATONIN TREATMENT

The case of a 41-year-old sighted man with non-24-hour sleep-wake synd rome is presented. A 7-week baseline assessment confirmed that the pat ient expressed endogenous melatonin and sleep-wake rhythms with a peri od of 25.1 hours. We sought to investigate the underlying pathology an d to entrain the patient to a normal sleep-wake schedule. No deficienc y in melatonin synthesis was found. Furthermore, normal coupling betwe en the melatonin and sleep propensity rhythms was documented using an ''ultrashort'' sleep-wake protocol. Environmental light exposure was m onitored for 41 days, and the circadian timing was calculated. Sensiti vity to photic input was determined with light-induced melatonin-suppr ession tests. Three intensities (500, 1,000, and 2,500 lux) were exami ned during three separate trials. The 2,500-lux trial resulted in 78% suppression, but the lesser intensity exposures were without substanti al effect. Thus, the patient appeared to be subsensitive to bright lig ht. A 4-week trial of daily melatonin administration (0.5 mg at 2100 h ours) stabilized the endogenous melatonin and sleep rhythms to a perio d of 24.1 hours, albeit at a somewhat delayed phase. A 14-month follow -up interview revealed that the patient continued to take melatonin da ily, and his sleep-wake schedule was stable to a near 24-hour schedule .