Everyone who cares for someone with Alzheimer's disease (AD) knows all too well that this condition is a thief who slowly steals the most precious parts of those they love. Their memories, ability to communicate, self expression, thinking and planning skills, and personality transform, fade, or eventually disappear.

Caring for someone throughout the stages of AD can leave caregivers feeling powerless, unprepared, and frustrated. Understanding how the disease affects the brain can help caregivers know more about what to expect as it progresses and how to prepare for the later stages. Reducing the amount of surprise involved can make this process less stressful and help caregivers to better look after themselves and their loved ones.

Remember that Alzheimer's disease is not natural aging. It is a progressive disease that causes the abnormal death of brain cells. The initial signs of dementia often include memory loss, but as the disease progresses, it affects more of the brain until the person is unable to move, swallow or breathe.

Main Parts of the Brain

The first step is to understand how a normal, healthy brain functions. This organ is nothing short of amazing. From its larger structures down to its tiniest cells, it is arguably the most important and the least understood organ in the human body.

The larger, easily visible structures of the brain include the cerebrum, the cerebellum and the brain stem. Scientists have also been able to map the general regions and lobes that control a person's skills and reactions, allowing them to better understand the progress of AD.


The cerebrum is the largest part of the organ and takes up most of the space in the skull. It contains the regions responsible for body movement, memory, problem solving, thinking skills, and feeling. No doubt you have already guessed that this is where the first afflicted brain cells begin to make their demise known.


Next, at the back of the skull just under the cerebrum sits the cerebellum. This part of the brain is responsible for the body's balance and coordination. Significant damage in this area occurs soon after cognitive thinking is diminished.

Brain Stem

The brain stem is the smallest structure of the three main regions of the brain. It sits beneath the cerebrum, in front of the cerebellum and connects the spinal cord to the brain. It controls the major physical functions necessary for life: breathing, heart rate, blood pressure and digestion.

In the Alzheimer's Brain

Scientists have identified several hallmark brain abnormalities in people affected by Alzheimer's:

  • Amyloid plaques, which are microscopic clumps of a protein called beta-amyloid peptide. These abnormal clusters of protein fragments build up between nerve cells which disrupts electrical signals. Diseased tissue has many fewer nerve cells and synapses compared to healthy brain tissue.
  • Dead and dying nerve cells contain neurofibrillary tangles, which are made up of twisted strands of another protein called tau (rhymes with "wow").
  • These plaques and tangles tend to spread through the cortex in a predictable pattern as AD progresses.
  • There is a profound loss of connections among brain cells called synapses. These connections transmit information from cell to cell and are responsible for memory, learning and communication.
  • Inflammation results from the brain's efforts to fend off the lethal effects of these and other neurological changes.
  • Brain cells eventually die, resulting in significant tissue shrinkage or atrophy.

Scientists are not absolutely sure what mechanism specifically causes cell death and tissue loss in a diseased brain, but plaques and tangles are the prime suspects.

There are several larger scale effects on the brain as well:

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  • The cerebral cortex (the outer layer of the cerebrum) shrivels up, damaging areas involved in thinking, language, consciousness and remembering.
  • Atrophy is especially severe in the hippocampus, an area of the cortex that plays a key role in the formation of new memories and spatial navigation.
  • Ventricles (fluid-filled spaces within the brain) may grow larger.

The Stages of Alzheimer's

All of the above processes have a devastating impact on the brain, and over time, it shrinks dramatically, affecting nearly all of its functions. The rate of progression of the disease varies greatly. People with Alzheimer's live an average of eight years, but some people may survive up to 20 years. The course of the disease depends in part on age at diagnosis and whether a person has other health conditions.

The medical community uses stages to apply a timeframe to the progression of the disease. It is important for family members to be aware of this in order to adequately prepare for increasing levels of care.

Preclinical Alzheimer's

Biological changes within the brain may begin 20 years or more before an actual diagnosis, but the person does not exhibit any symptoms at this stage.

Mild to Moderate Alzheimer's stages

Affected individuals in this stage begin to experience difficulty with thinking and memory that is noticeable to themselves and those around them. These symptoms will begin to affect daily life. This stage generally lasts anywhere from two to 10 years.

Severe Alzheimer's

In the final stage, individuals are typically unable to communicate, see to their own personal care, swallow or walk independently. This stage may last from one to five years.