Lewy Body Dementia (LBD) is the second most common dementia of the elderly. There is a strong need for tools to better distinguish Lewy Body Dementia from Alzheimer's disease (AD). This proposal is to combine two sorts of biomarkers, namely genotype and cerebrospinal fluid (CSF) protein analysis to develop a better tool to distinguish these two common dementias. We propose to recruit participants for CSF analysis and DNA genotyping for glucocerebrosidase (GBA) and apolipoprotein E (APOE). We have shown that GBA is a risk factor for LBD, and propose that combining CSF biomarker analysis with genotyping may allow distinction of LBD from AD.