Apathy: an underestimated feature in GBA and LRRK2 non-manifesting mutation carriers

BackgroundHigher prevalence of motor and non-motor features has been observed in non-manifesting mutation carriers of Parkinson’s Disease (PD) compared to Healthy Controls (HC).ObjectivesThe aim was to detect the differences between GBA and LRRK2 mutation carriers without PD and HC on neuropsychiatric symptoms.MethodsThis is a cross-sectional retrospective study of non-manifesting GBA and LRRK2 mutation carriers and HC enrolled into Parkinson’s Progression Markers Initiative (PPMI). Data extracted from the PPMI database contained: demographics and performance in MoCA scale and MDS-UPDRS scale part 1A (neuropsychiatric symptoms). All six features were treated as both continuous (MDS-UPDRS individual scores) and categorical variables (MDS-UPDRS individual score>0 and MDS-UPDRS individual score=0). Logistic regression analyses were applied to evaluate the association between mutation carrying status and neuropsychiatric symptoms.ResultsWe found that non-manifesting mutation carriers as a whole (total N=654, GBA: n=285, LRRK2: n=369) were 2.3 times more likely to present apathy compared to HC, even after adjustment for covariates (adjusted OR=2.3, 95% CI=1.1-5.0, p-value=0.027). The effect was mainly driven by GBA mutation carriers (adjusted OR= 2.6, 95% CI=1.1-6.3, p=0.031), while the higher percentage of apathy for LRRK2 carriers compared to HC was marginally non-significant. Other neuropsychiatric symptoms, such as psychotic or depressive manifestations, did not differ between groups.ConclusionsSymptoms of apathy could be present in the premotor period of LRRK2 and, especially, GBA mutation carriers. Longitudinal data, including detailed neuropsychiatric evaluation and neuroimaging, would be essential to further investigate the pathophysiological basis of this finding.