The actigraphic documentation of circadian sleep-wake rhythm dysregulation in myotonic dystrophy type 1

Study objectives: The present study aimed at identifying the sleep-wake rhythm in patients with myotonic dystrophy type 1 (DM1) compared to healthy controls. Methods: Patients with genetic diagnosis of DM1 and healthy controls underwent a 7-day actigraphic recording and filled out a daily sleep diary to evaluate the sleep-wake rhythm. All participants underwent a physical and neurological examination to exclude conditions interfering with the sleep-wake cycle. Daytime activity, nocturnal sleep, and non-parametric circadian rhythm activity (NPCRA) were analysed. Results: Twenty-nine patients affected by DM1 were included in the present study and were compared to 16 controls. Considering nocturnal actigraphic data, DM1 patients showed a longer time in bed, sleep period time, actual sleep time, and sleep latency compared to controls. Central phase measurement was significantly longer in DM1 patients than controls. At NPCRA analysis patients showed a lower degree of regularity in the activity-rest pattern compared to controls. Moreover, DM1 patients showed reduced motor activity during daytime and a lower synchronization of the rest-activity rhythm than controls. Conclusions: This study documented that patients with DM1 not only present the impairment of nocturnal sleep, but also show a dysregulation of the sleep-wake circadian rhythm; moreover, reduced amplitude of the circadian rhythmicity was also evident in comparison to controls, probably in relation to the reduced diurnal motor activity of patients. These findings add further evidence to the already documented sleep impairment and excessive daytime sleepiness in DM1 patients.