Alzheimer’s Disease: Causes, Stages, and Life Expectancy

Alzheimer’s disease is a progressive, irreversible brain disorder that slowly destroys memory and thinking skills. It is the most common cause of dementia, accounting for 60-80% of dementia cases. Here we will explore what happens in the brain to cause Alzheimer’s, the stages of the disease progression, and the average life expectancy after diagnosis.

What Happens in the Alzheimer’s Brain

Healthy Brain Function

In a healthy brain, neurons communicate through electrical signals that travel down axons, causing the release of chemicals to neighboring neurons across tiny gaps called synapses. Support cells like astrocytes and microglia help keep neurons healthy by clearing away debris. This allows sensations, movements, thoughts, memories and feelings to occur smoothly.

Alzheimer’s Brain Changes

In Alzheimer’s disease, toxic changes in the brain destroy this healthy balance. While the exact causes are still being investigated, two proteins seem to play a major role:

  • Beta-amyloid – This protein abnormally clumps into plaques that build up between neurons.
  • Tau – This protein accumulates inside neurons, forming tangles that disrupt neuronal communication.

As amyloid plaque levels reach a tipping point, tau spreads rapidly throughout the brain. But other factors like vascular problems, lack of brain glucose, and inflammation may also contribute over time.

Consequences in the Brain

The toxic Alzheimer’s changes first impair neurons in the hippocampus, the brain’s memory center. As more neurons die, the brain shrinks, beginning with the hippocampus. People start experiencing memory loss, confusion and problems with decision-making and language.

Eventually, widespread neuronal death impairs a person’s ability to think, remember, communicate and function independently. Understanding the molecular interactions is key to developing effective Alzheimer’s treatments.

Stages of Alzheimer’s Disease

There are five stages associated with the progression of Alzheimer’s disease:

1. Preclinical Stage

Years or decades before symptoms appear, toxic brain changes are underway. No symptoms are noticeable yet, even on testing. This stage can only be identified in research settings.

2. Mild Cognitive Impairment

Mild but measurable memory and thinking problems emerge, but daily functioning is still intact. It can take 2-5 years to progress from MCI to Alzheimer’s dementia.

3. Mild Dementia Stage

Memory lapses become more apparent, like forgetting familiar words or where objects were left. Interests and moods change. People may still function independently but have increasing difficulty with complex tasks.

4. Moderate Dementia Stage

Confusion and disorientation increase. Help is needed with daily activities and self-care. Suspicions, restlessness and outbursts can occur as well.

5. Severe Dementia

Memory continues to worsen, personality changes become more pronounced and physical functioning declines. Patients lose the ability to communicate, walk or swallow. Infections like pneumonia often cause death.

Life Expectancy for People with Alzheimer’s Disease

On average, people with Alzheimer’s disease live 8-12 years after diagnosis, though some may survive 20 years or more. The course of the disease varies between individuals based on factors like age, genetics, lifestyle and coexisting medical conditions. Early diagnosis allows patients and families more time to plan for the future and access available treatments and support services.

Alzheimer’s Buildup of Amyloid Plaques and Tau Tangles In The Brain

In summary, Alzheimer’s disease is characterized by the buildup of amyloid plaques and tau tangles in the brain, resulting in widespread neuronal dysfunction and death. It progresses through stages from preclinical to severe dementia over 8-12 years on average.

Understanding the complex mechanisms underlying Alzheimer’s will pave the way for more effective treatments to slow or even halt progression of this devastating disease.

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