Alzheimer’s disease is a progressive neurodegenerative disorder and the leading cause of dementia in older adults. It is characterized by memory loss, impaired thinking and behavioral changes that worsen over time as brain cells die and brain regions shrink.

Research has identified two hallmark protein abnormalities in the brains of people with Alzheimer’s. One is the buildup of beta amyloid outside neurons, where it forms sticky plaques that may disrupt communication between nerve cells and trigger inflammation. The other is the accumulation of abnormal tau protein inside neurons, forming tangles that interfere with the transport systems needed for cell survival.

Genetic studies show that rare inherited mutations can cause early onset Alzheimer’s, often before age 65, while common genetic variants, such as those in the APOE gene, modify risk for the more typical late onset form. However, genes do not determine fate, and lifestyle and vascular factors also influence risk.

Biological changes in the brain begin many years before symptoms appear, which has led to efforts to detect the disease in its earliest, preclinical stages using imaging and biomarkers in blood and cerebrospinal fluid. Current medications can temporarily improve or stabilize symptoms but do not cure the disease. Newer therapies aim to reduce amyloid or tau accumulation, with mixed but evolving results.

Preventive research focuses on controlling cardiovascular risk factors, staying mentally and socially active, exercising, and following healthy dietary patterns, which together may help delay the onset or progression of Alzheimer’s disease.