Connectivity between the insula and precuneus may be associated with cognitive function among patients with isolated rapid eye movement sleep behavior disorder (iRBD), according to the results of a cross-sectional study published in Sleep Medicine.
Study researchers recruited patients (n=50) diagnosed by video-polysomnography with iRBD at Seoul National University Hospital Sleep Clinic and healthy controls (n=20) for this study. They assessed participants by multivariate pattern analysis on the basis of structural magnetic resonance imaging (MRI) and resting-state functional MRI scans.
Patients with iRBD and those in the control group had a mean age of 66.5 (standard deviation [SD], ±6.9) and 68.1 (SD, ±3.4) years, respectively, and 58.0% and 55.0% were men, respectively. Patients had been diagnosed with iRBD an average of 7.1 (SD, ±4.6) years previously, and compared with controls had higher Rapid Eye Movement Sleep Behavior Disorder Questionnaire scores (P <.001), Geriatric Depression Scale scores (GDS; P =.001), Scales for Outcomes in Parkinson Disease-Automatic questionnaire scores (P =.001), and spent fewer years in education (P =.047).
The multivariate pattern analysis found 1 significant cluster located in the left posterior insular cortex and 2 located in the precuneus.
Patients with iRBD exhibited a positive correlation between the functional connectivity of the insular-precuneus cluster 1 and Montreal Cognitive Assessment (MoCA) scores (r, 0.317; P =.025). MoCA scores trended toward a positive correlation with functional connectivity of the precuneus cluster 2 (r, 0.271; P =.057).
GDS and MoCA scores were negatively correlated (r, -0.294; P =.038). After adjusting for GDS, MoCA scores correlated with the functional connectivity in both clusters in the precuneus (cluster 1: adjusted r, 0.337; P =.018; cluster 2: adjusted r, 0.371; P =.009).
Delayed recall was correlated with functional connectivity of cluster 2 in the left posterior insula (r, 0.282; P =.047) and was more strongly correlated after correcting for GDS (adjusted r, 0.333; P =.019).
This study was limited by its small sample size and the cross-sectional design, which did not allow for causative relationships to be assessed.
Study researchers concluded that their findings emphasized “the insula as an important neural correlate associated with iRBD… [Functional connectivity] changes may be a biomarker of incipient cognitive decline, and larger longitudinal studies will be necessary to confirm the causal relationship between FC changes and cognitive impairment in iRBD.”
Byun J-I, Cha KS, Kim M, et al. Altered insular functional connectivity in isolated REM sleep behavior disorder: a data-driven functional MRI study. Sleep Med. 2021;79:88-93. doi:10.1016/j.sleep.2020.12.038