Alzheimer's disease is a type of dementia, an umbrella term that refers to a collection of symptoms, including memory loss, cognitive impairment, and sudden behavior changes (see overview).

More than 55 million people worldwide have dementia (see stats here); Alzheimer's disease makes up nearly 70% of all cases. Old age is the greatest risk factor in developing Alzheimer's, though genetic components can lead to early onset.


The first case of Alzheimer's disease dates back to the turn of the 20th century when Dr. Alois Alzheimer came across 51-year-old Auguste Deter, struggling with sudden memory issues and aggressive, irrational behavior.

After Deter's death, Alzheimer examined her brain and found it had a strange collection of molecular pileups.

In a twist of fate, Alzheimer's findings were lost until 1995, when they were rediscovered and published in a translated version.


Scientists now know these "pileups" are created by two distinct molecular formations: plaques and tangles.

Plaques are made from the amyloid beta peptide, or A-beta, which forms when an amyloid precursor protein is split. The sticky A-beta can aggregate into complex molecules that pile up near neurons and elsewhere in the brain.

Tangles are misfolded proteins known as tau proteins. Regular tau helps support healthy neurons. Misfolded tau proteins can congregate inside neurons and spread across synapses into healthy neurons, where they can cause healthy tau to misfold.

It is unknown which molecule—plaques or tangles (or both, or something else)—is the primary driver of Alzheimer's. See a deep dive into the debate here.

As neurons lose their ability to communicate and die off, the brain shrinks. This shrinkage starts in the hippocampus, a part of the brain associated with memory and learning, and leads to impaired memory, communication, and decision-making.


Historically, Alzheimer's disease could only be diagnosed for certain once a person's brain was analyzed after death. Currently, there's no cure for Alzheimer's, and there's no single test to detect it.

Patients are now able to receive a diagnosis through medical examinations, including neuropsychological testing, brain imaging, and blood tests, the latter of which may assist with early diagnosis.

Treatments tend to focus on slowing the formation of, or breaking up, plaques or tangles. Some treatments have been shown to modestly slow the progression of symptoms, but none have halted or reversed the disease.

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Relevant articles, podcasts, videos, and more from around the internet — curated and summarized by our team

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The brain has three main parts—the cerebrum, brain stem, and cerebellum—each combining to control the entirety of the body’s operations. Alzheimer’s progressively deteriorates the circuitry in these structures, resulting in what we see as the symptoms of the disease. This rich visual guide illustrates the difference between a healthy brain and one afflicted by Alzheimer’s.

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A human deprived of sleep for a single night will see an immediate increase in amyloid beta proteins, the molecule behind plaques seen in Alzheimer’s. New studies reveal high-quality sleep is critical in preventing the buildup of the sticky protein that appears to play a role in the development and progression of the neurological disease.

Photo of two people talking with text overlay that reads, "Longing for Yesterday."
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This nine-minute short film attempts to answer the loaded question of what it feels like to fade into dementia, a degenerative neurological disease that causes memory, motor, and cognition issues. The focus of the Dutch film is Jos, a married father who previously worked in hospitality. It follows him as he sinks deeper into his dementia "during what feels like a single day. Or is it years?"

Older couple in black tie dress dance alone in the foreground while another couple looks on from the background.
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Among other challenges, memory loss associated with progressive dementia makes retention of one's life story difficult. This framing of the problem makes memory the key component of identity formation. But a different philosophical tradition argues even as our memory fades, the social relationships that define us do not, offering a more humane approach to caring for those suffering from dementia.

Photo of medical scan of human head and brain.
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Immediately, according to Alzheimer's researcher and investigator Karl Herrup. Alzheimer's eponymous researcher tied the existence of these strange plaques and tangles to the disease, a conclusion that still drives modern research. By establishing this assumption of causality where they may have just been correlation, the "field has been trapped," Herrup argues.

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One of the leading theories behind Alzheimer's disease hinges on the amyloid beta peptide, a protein in the brain that can misfold and cause insoluble clumps known as plaques that lead to neuron death. In 2022, bombshell accusations surfaced alleging one of the field’s most influential papers contained doctored images—potential misdirecting years of research and millions in funding.

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