🧠 Health & Neurology
Alzheimer’s: what happens in the brain and why is this disease on the rise?
One of the most feared diseases of our time still holds many mysteries — but science already knows a great deal about how it begins and what increases the risk of developing it.
Introduction
A silent disease that begins long before the first symptoms appear
Imagine waking up one day and not remembering where you put your keys. Then starting to forget the names of people close to you. Eventually, no longer recognizing the face of someone you love. This is the reality for millions of people around the world living with Alzheimer’s disease — and for the families who surround them.
Alzheimer’s is far more than simple “memory lapses” caused by old age. It is a disease. A serious, progressive, and still incurable medical condition that gradually destroys the brain cells responsible for our memory, our ability to reason, to communicate, and to take care of ourselves.
In 2024, the World Alzheimer Report — produced by Alzheimer’s Disease International in partnership with the London School of Economics — revealed that 80% of people still mistakenly believe that dementia is a natural consequence of aging. This misconception is dangerous: when the disease is seen as “just getting old,” diagnosis is delayed, treatment comes too late, and the patient’s quality of life deteriorates unnecessarily.
What it is
What actually happens inside the brain of someone with Alzheimer’s?
To understand the disease, we first need to understand a little about how our brain works. It is made up of billions of cells called neurons, which communicate with each other like an extraordinarily sophisticated electrical network. This network is what allows us to remember things, learn, feel emotions, and make decisions.
In Alzheimer’s, this network begins to be destroyed by two types of “debris” that accumulate in the brain over many years — sometimes decades before the first symptoms appear.
The first is the buildup of a protein called beta-amyloid, which forms small plaques between neurons, blocking communication between them. The second is the tangling of another protein called tau, which normally keeps the internal structure of neurons organized — but in the disease becomes dysfunctional and kills cells from the inside out.
The result is that neurons begin to die. And when they die, the functions they performed — memories, abilities, parts of personality — go with them.
One of the most striking discoveries in recent years is that this destructive process begins in the brain 15 to 20 years before any visible symptoms appear. In other words: by the time a person starts forgetting things, the disease has already been present for a long time.
The numbers in the US
Why does the United States need to pay attention to this now?
According to the Alzheimer’s Association’s 2024 Facts and Figures report, approximately 7.2 million Americans are currently living with Alzheimer’s disease. About 1 in 9 people aged 65 and older has the condition — and that proportion rises sharply with age: one in three people over 85 is affected.
The trajectory is alarming. Deaths from Alzheimer’s have more than doubled between 2000 and 2024, while deaths from heart disease — the leading cause of death — have decreased. The disease is currently the sixth leading cause of death in the United States, claiming over 116,000 lives per year according to CDC data.
By 2060, projections estimate that as many as 13.8 million Americans could be living with Alzheimer’s — nearly double today’s numbers. And the financial toll is staggering: in 2024, unpaid family caregivers provided an estimated 19.2 billion hours of care, valued at over $413 billion.
Causes and risk factors
Why do some people develop Alzheimer’s and others don’t?
This is the question scientists are most eager to answer. And the honest answer is: there is no single cause. Alzheimer’s is what medicine calls a multifactorial disease — meaning it results from a combination of factors accumulated over a lifetime.
Think of it like a glass of water. Each risk factor is a drop. The disease appears when the glass overflows. Some people have larger glasses (due to genetics or other protective factors), others have smaller ones. The good news is that we can control many of those drops.
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Age and genetics. The primary risk factor for Alzheimer’s is simply getting older. The disease rarely appears before age 65, and after that the risk roughly doubles every five years. There is also a genetic component — particularly a gene called APOE-e4, strongly associated with late-onset Alzheimer’s. However, carrying this gene does not inevitably lead to the disease.
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Cardiovascular conditions. High blood pressure, diabetes, obesity, and high cholesterol damage the brain’s blood vessels and create an environment where the disease can thrive. Research from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) — a project running for over 20 years across hundreds of American institutions — showed that brain vascular health is one of the most determining factors in Alzheimer’s progression.
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Sedentary lifestyle and poor diet. Studies on the Mediterranean diet — rich in olive oil, fish, fruits, vegetables, and whole grains — suggest that people who follow this eating pattern may reduce their risk of cognitive decline by up to 33%. Regular physical activity has a similar effect: it stimulates the production of proteins that protect neurons and improves blood flow to the brain.
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Mental health and social isolation. Untreated depression throughout life and chronic social isolation are recognized risk factors. The brain needs constant social and emotional stimulation. People who maintain active social lives, keep learning new things, and engage in cognitive activities tend to show lower risk — or at least a later onset of symptoms.
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Poor sleep quality. During deep sleep, the brain performs a kind of “cleaning” of proteins that accumulated throughout the day — including beta-amyloid, linked to Alzheimer’s. When sleep is chronically disrupted or insufficient, this cleaning process doesn’t work properly, and the plaques accumulate faster.
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Smoking, alcohol, and air pollution. Smoking damages brain blood vessels and increases oxidative stress in neurons. Excessive alcohol consumption over a lifetime is also linked to higher risk. More recently, research has begun identifying air pollution — especially in large urban areas — as an environmental factor contributing to neuroinflammatory processes connected to Alzheimer’s.
An analysis published in 2023 in JAMA Network Open, involving researchers from dozens of European universities, concluded that controlling modifiable risk factors — such as high blood pressure, diabetes, obesity, physical inactivity, smoking, and depression — could prevent up to 45% of Alzheimer’s cases. That means nearly half of future diagnoses could potentially be avoided through lifestyle changes.
Final reflection
What can we do with this knowledge?
Understanding Alzheimer’s is the first step — and that is exactly why articles like this one matter. The earlier people understand what the disease is, what promotes it, and what can be done to reduce the risk, the sooner they can adopt habits that protect the brain over the long term.
There is no absolute guarantee that anyone will never develop Alzheimer’s. But science is clear: lifestyle matters — and it matters a lot. Taking care of your heart, your sleep, your mind, and your social relationships is not just good for general well-being. It is, literally, taking care of your brain.