Background: A recent case study reported a non-24 h sleep-wake disorder in a patient with myotonic dystrophy type 1 (DM1). Research on intrinsic circadian rhythm sleep-wake disorders (CRSWDs) in DM1 patients is though lacking. This study utilized actigraphy to ascertain the presence of CRSWDs in DM1 patients and establish a comparison with healthy control subjects.
Methods: Thirty-three patients with genetic diagnosis of DM1 and 33 age- and sex-matched healthy control subjects wore an actigraph and filled out a sleep diary for two consecutive weeks. Sleep, light exposure, and nonparametric measures were computed from actigraphic data.
Results: DM1 patients exhibit poorer sleep quality and delayed sleep-wake episodes as well as reduced daylight exposure compared to healthy control subjects. Importantly, 3 DM1 patients (9.1 %) had a delayed sleep phase disorder and 3 DM1 patients had an irregular sleep-wake rhythm disorder (ISWRD) (9.1 %) whereas no control subject exhibited a CRSWD. DM1 patients with an ISWRD presented lower inter-daily stability (IS) (0.16 vs. 0.44, p < 0.05) and relative amplitude (RA) (0.36 vs. 0.79, p < 0.01) as well as higher intra-daily variability (IV) (1.22 vs. 0.79, p < 0.05) than DM1 patients with a normal sleep phenotype. DM1 patients with CRSWDs were more likely to exhibit excessive daytime sleepiness (EDS) than those with a normal sleep phenotype (83.3 % vs. 37.0 %, p < 0.05).
Conclusions: Core clinical implications are the need to systematically screen DM1 patients for CRSWDs and apply a multimodal chronotherapy (sleep hygiene, timed light, and melatonin). Recognizing and treating CRSWDs can help address significant sleep disturbances, like EDS.
Keywords: Actigraphy; Circadian rhythm sleep-wake disorders; Delayed sleep phase disorder; Excessive daytime sleepiness; Irregular sleep-wake rhythm disorder; Myotonic dystrophy type 1.
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