Non-motor symptoms are associated with REM sleep behavior disorder in Parkinson’s disease: a systematic review and meta-analysis

Objective Parkinson’s disease (PD) is usually accompanied by rapid eye movement sleep behavior disorder (RBD). A systematic review has concluded that motor manifestations are associated with RBD in PD patients, but whether the same is true of non-motor symptoms is unclear. Methods A systematic review and meta-analysis was conducted by searching studies related to PD and RBD in PubMed, Web of Science, Embase, and Cochrane databases. Data were pooled where appropriate and used to calculate odds ratios (ORs), mean differences (MDs), or standardized mean differences (SMDs) with 95% confidence intervals (CI). Heterogeneity was assessed using the I 2 statistic. Results PD patients with RBD were more likely to be male (OR 1.26, 95% CI 1.14–1.40) and older (MD 1.70 years, 95% CI 1.24–2.16) than those of patients without RBD. Patients with RBD were at a higher risk of non-motor symptoms such as constipation (OR 1.94, 95% CI 1.57–2.38), hallucination (OR 2.62, 95% CI 2.01–3.41), depression (SMD 0.39, 95% CI 0.25–0.53), and cognitive impairment (SMD − 0.29, 95% CI − 0.42 to − 0.17) based on standardized questionnaire scores. Similarly, PD patients with RBD suffered more severe motor symptoms and required higher doses of levodopa therapy. Conclusions The available evidence suggests that PD patients with RBD suffer severer non-motor and motor symptoms than those without RBD. A potential explanation is that PD patients with RBD present more diffuse neurodegeneration.