Alzheimer’s disease

What happens in the brain

Alzheimer’s disease is defined by two abnormal protein deposits: plaques of amyloid beta between neurons and tangles of tau inside them. According to the National Institute on Aging, these changes are accompanied by chronic inflammation, loss of connections between neurons, vascular problems and, eventually, widespread neuron death and brain shrinkage. The changes begin years, probably decades, before the first symptoms.

The disease typically starts in regions important for memory, including the hippocampus and entorhinal cortex, which is why recent memory is usually affected first. Over time it spreads to regions responsible for language, reasoning and social behaviour.

The scale of the problem

The Alzheimer’s Association’s 2026 Facts and Figures report estimates 7.4 million Americans aged 65 and older living with Alzheimer’s dementia and projects $409 billion in US health and long-term care payments in 2026, a figure that excludes the enormous contribution of unpaid family caregivers. Globally, the World Health Organization estimates that 57 million people were living with dementia in 2021, with nearly 10 million new cases each year, and that Alzheimer’s accounts for 60 to 70 percent of them.

Where clearance fits

Amyloid beta was the first waste product shown to travel the glymphatic route in the 2012 Iliff study, and its clearance roughly doubled during sleep in the 2013 Xie study. Human studies have since linked poor sleep to higher amyloid burden, and glymphatic function declines with the same ageing process that is the biggest risk factor for Alzheimer’s. Whether restoring clearance can change the course of the disease is unproven, but it is one of the reasons the field is watching clearance research closely.

What can be done today

Recently approved antibody therapies can remove amyloid and modestly slow decline in early disease, with meaningful side-effect considerations. Beyond medication, the 2024 Lancet Commission’s fourteen modifiable risk factors remain the most broadly applicable guidance, and early diagnosis helps families plan. Anyone concerned about their memory should talk to a clinician; this page is background, not medical advice.

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