Short answers, pulled from the story.
Alzheimer's disease is a neurodegenerative disease and the most common form of dementia, accounting for around 60 to 70 percent of cases. Its causes remain poorly understood, but it is characterized by the accumulation of misfolded amyloid beta in plaques outside neurons and tau protein in neurofibrillary tangles inside them. The strongest genetic risk factor is the APOEε4 allele of apolipoprotein E.
The most common early symptom of Alzheimer's disease is difficulty remembering recent events, since the disease first targets the hippocampus. It progresses through three stages described as early or mild, middle or moderate, and late or severe. In the late stage there is complete dependence on caregivers, with speech reduced to single words and eventual loss of the ability to feed oneself.
Alzheimer's disease is named after German psychiatrist and pathologist Alois Alzheimer, who identified the first case in 1901 in a fifty-year-old woman he called Auguste D. He followed her until she died in 1906, when he first reported publicly on it. The disease was later described as distinctive by Emil Kraepelin in his Textbook of Psychiatry.
There is no cure for Alzheimer's disease, and no treatments can stop or reverse its progression, though some may temporarily improve symptoms. Acetylcholinesterase inhibitors such as donepezil and the NMDA antagonist memantine offer only small benefits. A 2026 meta-analysis found that anti-amyloid antibodies have no effect, and a 2026 Cochrane review found no effect or at best a small one.
As of 2020 there were approximately 50 million people worldwide with Alzheimer's disease. The prevalence is estimated to triple by 2050, reaching 152 million. It most often begins in people over 65, affects about 6 percent of people 65 and older, and affects women more often than men.
Women are affected by Alzheimer's disease more often than men, and as of 2025 the reason is still unknown. The gap was long attributed to women's longer lifespans, but the Framingham study found women with almost twice the lifetime risk of men. Tau protein also accumulates faster in women, and the APOE4 allele raises risk more in women than in men.
Alzheimer's disease can only be definitively diagnosed at autopsy by examining brain tissue for plaques and tangles, so living patients receive a clinical diagnosis of possible or probable Alzheimer's based on medical history, cognitive testing, and observations from relatives. Imaging with MRI, CT, or PET helps rule out other causes. In May 2025 the FDA approved a blood test, the Lumipulse G pTau217 amyloid ratio device, for early detection in adults aged 55 and older.