GBA1 and Parkinson disease: Carriers of the common E326K variant have been shown to have an increased risk of dementia and motor progression in comparison with non-carriers in one US-based study.20 However, in a large meta-analysis of GBA1 variants in PD, there was no association between development of PD and the E326K variant.4 This study population was enriched for individuals from Jewish, Portuguese and Asian populations, in which the E326K accounts for a lower proportion of GBA1 variants than in other populations, which may account for the lack of association in this analysis.3 30