Lack of bidirectional association between age‐related macular degeneration and Alzheimer's disease: A Mendelian randomization study

Introduction Observational studies have reported inconsistent results on the relationship between age‐related macular degeneration (AMD) and Alzheimer's disease (AD). Therefore, we aimed to determine whether there is a causal association between AMD and AD. Methods This two‐sample bidirectional Mendelian randomization (MR) study evaluated causal associations between advanced AMD and AD using summary data from large genome‐wide association studies. Results Genetic liability for advanced AMD showed no statistical causal association with AD risk (odds ratio [OR] = 0.999, 95% confidence interval [CI]: 0.955–1.044, P = .948). Reverse MR analysis provided little support for a causal effect of AD on advanced AMD (OR = 0.973, 95%CI: 0.938–1.008, P = .133). Discussion This MR study found no evidence to support a bidirectional causality between advanced AMD and AD. Highlights We evaluated the bidirectional causal relationship between advanced AMD and AD. Advanced AMD showed no statistical causal association with risk of AD. We found no evidence to support a causal effect of AD on advanced AMD risk. The associations observed in epidemiological studies should not be considered causal.