Somnolence, insomnia not predictive of neurodegeneration in idiopathic RBD
Neither somnolence nor insomnia can be used as predictive markers of neurodegenerative disease, such as Parkinson’s disease and dementia with Lewy bodies, in patients with idiopathic REM (rapid eye movement) sleep behaviour disorder (RBD), according to a study.
The prospective cohort study included 151 RBD patients (mean age 66.4 years; 75 percent male) and 85 controls (mean age 68.9 years; 74 percent male). Assessments included the Epworth sleepiness scale (ESS), the Insomnia Severity Index (ISI), the Pittsburgh Sleep Quality Index (PSQI) and polysomnogram. All participants had at least one baseline sleep analysis.
Results for ESS did not differ between the RBD patients and controls (mean score, 7.0 vs 7.2, respectively; p=0.77), and the scores did not progress with time (change, 0.46; p=0.45). ESS scores were comparable between the patients who developed neurodegenerative disease and those who remained disease-free (mean, 6.7 vs 7.1, respectively; p=0.70).
PSQI scores, on the other hand, were notably higher in patients than in controls (mean, 7.2 vs 4.9; p=0.004), mainly driven by the sleep disturbance/medication components (reflecting RBD symptoms/treatment). While baseline Pittsburgh scores did not predict neurodegeneration in RBD patients, sleep duration increased over time in those who developed neurodegenerative disease (change, 0.88 hours; p = 0.014).
ISI scores were also higher in patients than in controls (mean, 10.0 vs 6.35; p<0.001). But unlike those of PSQI, ISI scores declined over time (change, −1.43; p=0.029) especially in patients who developed a neurodegenerative disease.
Finally, on polysomnogram, RBD patients who developed neurodegeneration had higher tonic REM compared with their counterparts who remained disease-free (58.4 vs 46.1; p=0.019). On Cox analysis, increased tonic REM was associated with an 88-percent increase in the risk of developing defined neurodegenerative disease (p=0.039).
“Daytime somnolence and insomnia are common features of neurodegenerative synucleinopathies,” researchers said. Insomnia occurs in up to 50 percent of PD patients, whereas somnolence occurs in 30 to 40 percent of PD and 40 to 70 percent of DLB patients.
Regardless of the difference in time of onset, both sleep disorders can be seen at diagnosis, suggesting that they may be present in prodromal disease, researchers said.
Findings of the present study, however, indicate that somnolence and insomnia do not predict the development of neurodegenerative disease in RBD patients.