Alzheimer's disease: A comprehensive review of epidemiology, pathophysiology, diagnosis, and treatment.

Alzheimer's disease (AD) is the most common cause of dementia, representing a major global public health challenge as populations age. It accounts for roughly 60%-80% of all dementia and is characterized by progressive cognitive decline, memory impairment, and eventual loss of independence in daily functioning. The disease unfolds over decades, with neuropathological alterations preceding the onset of clinical symptoms by many years. Alzheimer's disease is closely linked to the accumulation and deposition of cerebral amyloid-β (Aβ) and represents the most common cerebral amyloid deposition disorder. Recent advances in molecular biology, neuroimaging, and biomarker science have revealed a complex, multifactorial pathogenesis involving protein misfolding, neuroinflammation, synaptic dysfunction, vascular factors, and network-level propagation of pathology. This review synthesizes current knowledge on AD terminology, epidemiology and risk factors, clinical phenotypes and natural history, pathophysiological mechanisms, diagnostic approaches (including imaging and fluid biomarkers), and established as well as emerging therapeutic strategies, while also outlining key challenges and future directions.