Disordered REM sleep, constipation signal cognitive decline among Parkinson’s disease patients

Constipation and probable REM* sleep behaviour disorder (RBD) are strong indicators of future cognitive decline in Parkinson’s disease (PD) patients, especially in men, a recent study has found.

Drawing from the Parkinson’s Progression Markers Initiative, researchers enrolled 360 newly diagnosed, untreated PD patients (mean age, 61.23±9.75 years). The Scale for Outcomes in PD for Autonomic Symptoms (SCOPA-AUT) questionnaire was used to evaluate constipation, while pRBD was ascertained using the REM Sleep Behaviour Disorders Screening Questionnaire (RBDSQ).

At the 5-year follow-up, 281 PD patients provided information for analysis, of whom 189 were men and 92 were women. Scores on several neuropsychological tests, such as the Montreal Cognitive Assessment (MoCA; p=0.01), Symbol Digit Modalities Test (SDMT; p<0.001), Letter Number Sequencing (LNS; p=0.01), and semantic fluency (p<0.001), were all significantly better in women.

Linear mixed-effect modelling showed that at baseline, RBDSQ scores in men correlated significantly with SDMT scores over 5 years of follow-up (p=0.009). No such interaction was reported for the other neuropsychological measures, nor was baseline constipation significantly predictive of any cognitive outcomes.

However, when both constipation and pRBD were dichotomized, the interaction between both variables was found to be significantly correlated with SDMT scores in men (p<0.001). In addition, after excluding PD patients with MoCA scores <26, SDMT (p<0.001), LNS (p=0.003), and Hopkins Verbal Learning Test-Revised retention (p=0.01) likewise correlated significantly with both constipation and pRBD in men.

In women, pRBD was associated with MoCA scores (p=0.005) and semantic fluency (p=0.005), while constipation was correlated with MoCA scores alone (p=0.003).

* Rapid eye movement