Refining the link between REM sleep behavior disorder and neurodegeneration: Genetic correlation, Mendelian randomization, and colocalization evidence

Observational studies have proposed a link between isolated rapid eye movement sleep behavior disorder (iRBD) and several neurodegenerative diseases. We employed genome-wide linkage disequilibrium score regression (LDSC), standard two-sample Mendelian randomization (MR), and colocalization analysis to assess the causal links between iRBD and these neurodegenerative conditions. iRBD demonstrated a positive causal association with Alzheimer disease (odds ratio [OR] = 1.02, 95% confidence interval [CI]: 1.00–1.03, P = 1.10E−02), Parkinson disease (OR = 1.10, 95% CI: 1.03–1.16, P = 2.96E−03), and multiple sclerosis (OR = 1.09, 95% CI: 1.02–1.17, P = 1.61E−02). A strong positive genetic correlation with dementia with Lewy bodies was observed (rg = 1.6313, P = .0002), along with a causal association (OR = 1.45, 95% CI: 1.03–2.06, P = 3.53E−02), further supported by colocalization analysis. No significant causal relationship was identified between iRBD and amyotrophic lateral sclerosis (all P > .05). Additionally, reverse Mendelian randomization analyses did not reveal any causal relationships between the neurodegenerative diseases studied and iRBD. Our findings provide robust genetic evidence supporting a causal relationship between iRBD and the risk of multiple neurodegenerative diseases, highlighting the potential for shared pathophysiological mechanisms.