Identify the impact of prodromal RBD in the incidence of cognitive impairment in patients with early PD.

The association between sleep disorders and cognitive impairment is well-established, as well as the connection between sleep disorders and neurodegenerative dementia. Given the lack of efficacious interventions for cognitive impairment in Parkinson’s disease (PD), preventive strategies are crucial for reducing their cognitive burden.

We studied patients from the Parkinson’s Progression Markers Initiative (PPMI, www.ppmi-info.org) study enrolled within 2 years of motor symptom onset. We classified RBD status based on a cut-off score of five or higher on the RBD Screening Questionnaire at enrollment. We compared the mean scores of each group’s cognitive tests. Then, we conducted a survival analysis to compare time-to-onset of new cognitive impairment, and we fitted a logistic regression model with cognitive impairment as the outcome variable.

In patients with early RBD we observed a and a statistically significantly lower MoCA score (p=0.035) and lower symbol-digit modality test (p < 0.001). We also found a higher prevalence of cognitive impairment in patients with early RBD (p < 0.001), and an earlier onset of new cognitive impairment in the survival analysis (log-rank test p < 0.001). The Cox regression showed a hazard ratio (HR) of 1.22 (1.01-1.48, p < 0.001) for the presence of early RBD. The best logistic regression model estimated an odds ratio of 13.9 for RBD as a predictor of cognitive impairment, with variance inflation factor under five and an area under the receiver-operator curve of 0.6.

Cognitive impairment is more prevalent among patients with prodromal RBD. This may be attributed to impaired sleep quality, affective disorders that often co-occur with RBD, or intrinsic biological factors. This finding underscores the need for early cognitive assessment and lifestyle interventions that mitigate cognitive decline in this population.