Alzheimer's disease (AD) is characterized by irreversible changes, including abnormal accumulation of amyloid-β, and early detection and intervention are the most effective measures. Interestingly, olfactory dysfunction is a known early symptom of AD, and clinical applications of olfactory function in the diagnosis and treatment of dementia are beginning to be explored. However, scientific evidence supporting their validity is limited. This study aims to investigate the causal relationship between olfactory dysfunction and AD and to establish the basis for disease-modifying therapies via the olfactory circuit.