DM1 patients exhibit poorer sleep quality, delayed sleep-wake episodes, and reduced daylight exposure compared to healthy controls, with 18.2% presenting circadian rhythm sleep-wake disorders (delayed sleep phase disorder or irregular sleep-wake rhythm disorder), suggesting the need to systematically screen DM1 patients for CRSWDs.
DM1 patients exhibited poorer sleep quality compared to healthy control subjects.
DM1 patients showed delayed sleep-wake episodes compared to healthy control subjects.
DM1 patients had reduced daylight exposure compared to healthy control subjects.
9.1% of DM1 patients had delayed sleep phase disorder and 9.1% had irregular sleep-wake rhythm disorder (ISWRD), while no control subjects exhibited any circadian rhythm sleep-wake disorder.
DM1 patients with ISWRD showed significantly lower inter-daily stability and relative amplitude, and higher intra-daily variability compared to DM1 patients with a normal sleep phenotype.
DM1 patients with circadian rhythm sleep-wake disorders were significantly more likely to exhibit excessive daytime sleepiness than those with a normal sleep phenotype.
The authors recommend systematic screening for CRSWDs in DM1 patients and application of multimodal chronotherapy.
This research suggests that people with myotonic dystrophy type 1 (DM1), a genetic neuromuscular disease, have significant problems with their sleep and internal body clocks compared to healthy individuals. Using wrist-worn activity monitors (actigraphs) over two weeks, the researchers found that DM1 patients slept worse, tended to fall asleep and wake up later than normal, and were exposed to less daylight — all factors that can disrupt the body's natural 24-hour rhythms. Importantly, about 18% of DM1 patients (6 out of 33) had a formal circadian rhythm sleep-wake disorder: half had delayed sleep phase disorder (their sleep timing is shifted too late) and half had irregular sleep-wake rhythm disorder (their sleep is fragmented and unpredictable throughout the day and night). None of the healthy control participants had any such disorders. The study also found that DM1 patients with these circadian disorders were much more likely to suffer from excessive daytime sleepiness — a debilitating symptom already common in DM1. Patients with irregular sleep-wake rhythm disorder could be distinguished from other DM1 patients using specific actigraphy measurements reflecting how consistent and structured their daily activity-rest patterns were. These findings are notable because circadian rhythm problems in DM1 have rarely been studied before, even though they could be a major but overlooked contributor to the fatigue and sleep problems these patients experience. This research suggests that doctors caring for DM1 patients should routinely check for circadian rhythm sleep disorders, not just more commonly recognized sleep problems like sleep apnea. Identifying these disorders could open the door to targeted treatments such as carefully timed light exposure, melatonin, and improved sleep habits — approaches collectively called chronotherapy — which may help reduce daytime sleepiness and improve quality of life for DM1 patients. Because this was an exploratory study with a relatively small sample, larger studies are needed to confirm these findings.
Laberge L, Turcotte O, Angeard N, Maltais A, Martin J, Gagnon C. (2026). Endogenous circadian rhythm sleep disorders through the lens of nonparametric variables of actigraphy: an exploratory study in myotonic dystrophy type 1.. Sleep medicine. https://doi.org/10.1016/j.sleep.2026.108781