Genetic evaluation of dementia with Lewy bodies implicates distinct disease subgroups

The APOE locus is strongly associated with risk for developing Alzheimer’s disease and dementia with Lewy bodies (DLB). In particular, the role of the APOE ε4 allele as a putative driver of α-synuclein pathology is a topic of intense debate. Here, we performed a comprehensive evaluation in 2,466 DLB cases versus 2,928 neurologically healthy, aged controls. Using an APOE-stratified genome-wide association study approach, we found that GBA is associated with risk for DLB in patients without APOE ε4 (p = 6.58 x 10−9, OR = 3.41, 95% CI = 2.25–5.17), but not with DLB with APOE ε4 (p = 0.034, OR = 1.87, 95%, 95% CI = 1.05–3.37). We then divided 495 neuropathologically examined DLB cases into three groups based on the extent of concomitant Alzheimer’s disease co-pathology: pure DLB (n = 88), DLB with intermediate Alzheimer’s disease co-pathology (DLB + iAD, n = 66), and DLB with high Alzheimer’s disease co-pathology (DLB + AD, n = 341). In each group, we tested the association of the APOE ε4 against the 2,928 neurologically healthy controls. Our examination found that APOE ε4 was associated with DLB + AD (p = 1.29x10−32, OR = 4.25, 95% CI = 3.35–5.39) and DLB + iAD (p = 0.0011, OR = 2.31, 95% CI = 1.40–3.83), but not with pure DLB (p = 0.31, OR = 0.75, 95% CI = 0.43–1.30). In conclusion, though deep clinical data were not available for these samples, our findings do not support the notion that APOE ε4 is an independent driver of α-synuclein pathology in pure DLB, but rather implicate GBA as the main risk gene for the pure DLB subgroup.