Patients with early relapsing–remitting multiple sclerosis display a more marked motor wake inertia than healthy controls.
Sleep inertia is the transitional state between sleep and wake, characterized by impaired performance, reduced vigilance, and a desire to return to sleep, while motor wake inertia is the motor activity pattern during the transition between wakefulness and sleep.
Research has described the time course of dissipation of motor sleep inertia and motor wake inertia in healthy controls; however, there’s a lack of corresponding data for early relapsing–remitting multiple sclerosis (RRMS) patients. A study published in the journal Sclerosis compared these parameters in RRMS patients and healthy controls (HCs).
A total of 35 early RRMS patients and 35 HCs were enrolled. The patients and HCs were matched by age and gender, with a mean age of 31.51 and 31.29 years, respectively, and 24 females in each group.
HCs and Early RRMS Patients Dissipate Motor Sleep Inertia Similarly
Regarding the time course of motor sleep inertia dissipation, the functional linear modeling (FLM) analysis revealed a unique time interval with significant differences in motor activity between the two groups. This time interval was between 80 and 90 minutes after the wake-up time, during which the motor activity of early RRMS patients was significantly higher than the motor activity of HCs. It was concluded that motor sleep inertia dissipation is not different in early RRMS patients compared to HCs, as this difference occurs later than the time taken for motor sleep inertia dissipation in healthy controls, i.e., 70 minutes from wake-up time.
Early RRMS Patients Have More Motor Wake Inertia Than HCs
The FLM analysis regarding the time course of motor wake inertia dissipation revealed two time intervals after bedtime, with significant differences between the patients and HCs. These time intervals were between a few minutes after bedtime up to approximately 30 minutes after it and up to approximately 85 minutes after bedtime.
During these intervals, the RRMS patients demonstrated higher motor activity than HCs. Since the motor wake inertia dissipation has been reported to occur at 20 minutes after bedtime in healthy controls, it was inferred that motor wake inertia is more marked in early RRMS patients than HCs.
Possible Causes of Early RRMS Motor Wake Inertia Dissipation Slowness
Using the two-process model of sleep regulation as a theoretical framework, the slower dissipation of motor wake inertia in RRMS patients could be interpreted as a consequence of lower homeostatic sleep pressure in early RRMS. Moreover, this pattern is also compatible with the hyperactive hypothalamus–pituitary–adrenal axis in RRMS patients.
Tonetti, L., Camilli, F., Giovagnoli, S., Lugaresi, A., & Natale, V. (2023). Dissipation of motor sleep inertia and motor wake inertia in Early Relapsing–Remitting Multiple sclerosis. Sclerosis, 2(1), 1–6. https://doi.org/10.3390/sclerosis2010001