Increased frequency of the LRRK2 G2019S mutation in an elderly Ashkenazi Jewish population is not associated with dementia

Mutations in leucine-rich repeat kinase 2 gene (LRRK2) have been associated with idiopathic Parkinson's disease (PD), as well as pleomorphic neurodegenerative pathology, including Alzheimer's disease. One specific LRRK2 mutation, G2019S, was reported in 18% of people with PD of Ashkenazi descent, supporting a founder effect in this population. To determine if this mutation is also associated with dementia in the Ashkenazim, we screened 192 elderly Ashkenazi Jewish (AJ) individuals in a longitudinal aging and cognition study, of whom 49 (25.5%) had dementia. Two non-demented individuals harbored the mutation (2/143, 1.4%), but no individuals with dementia. Neither person with the mutation had Parkinson's disease. Therefore, the LRRK2 mutation has a relatively high frequency in the AJ population, is not fully penetrant for parkinsonism in the elderly, and does not appear to be commonly associated with late-onset dementia.