Objective: To explore the association between mild behavioral impairment (MBI) and disease severity in a predefined prospective cohort with Lewy body disease (LBD) spectrum

Background: MBI is reported to be common in non-demented Parkinson’s disease (PD) patients, being associated with motor deficits. The presence of MBI in prodromal stage PD might have clinical and prognostic values, which has not been investigated so far.

Method: This study included 35 polysomnography-confirmed idiopathic REM sleep behavior disorder (iRBD), 29 PD, and 20 dementia with Lewy bodies (DLB) patients. Patients were evaluated with the MDS-Unified Parkinson’s Disease Rating Scale (MDS-UPDRS), a validated neuropsychological battery, and MBI Checklist (MBI-C). We investigated the relationship between MBI and prodromal risk factors in iRBD patients, and explored the association between MBI and clinical severity in PD and DLB patients.

Results: The MBI score showed an increasing trend from iRBD to PD, and then DLB groups (p<0.001). Among 35 iRBD patients, 20 were classified as MBI-high and 15 as MBI-low. iRBD patients with MBI-high exhibited more prevalent prodromal markers such as anxiety, apathy, mild parkinsonian sign, mild cognitive impairment, autonomic dysfunction and hyposmia than the iRBD with MBI-low. The MBI showed moderate diagnostic value in iRBD patients in discriminating individuals with multiple prodromal markers from those without (AUC=0.675, sensitivity=64.3%, specificity=71.4%). MBI scores were correlated with anxiety (r=0.413, p=0.014), and apathy (r=0.405, p=0.016) scores in the MDS-UPDRS, as well as with the Geriatric Depression Scale scores (r=0.559, p=0.001) in iRBD patients. In PD patients, a negative correlations were observed in cognitive domains, particularly in the executive (r=-0.443, p=0.018) and visuospatial functions (r=-0.423, p=0.022), along with the MBI scores. Additionally, positive correlations were confirmed with UPDRS total score and MBI in PD patients (r=0.698, p=0.000). In DLB patients, there were negative correlations between global cognition and MBI scores (r=-0.673, p=0.001).

Conclusion: This study shows that the MBI-C is a useful questionnaire reflecting clinical severity in individuals with the LBD spectrum. Further studies are needed to reveal whether the MBI-C can be used in monitoring disease progression and can predict future phenoconversion in iRBD patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/mild-behavioral-impairment-in-lewy-body-disease-a-potential-marker-of-phenoconversion-and-disease-severity/