Diagnosing the Stages of Alzheimer's

Causes of Alzheimer’s Disease

Although the medical community is still trying to identify the exact cause of Alzheimer's disease and how to cure it, researchers believe that Alzheimer’s disease may result from a combination of genetics, environment and lifestyle that leads to a cascade of damage to the cells of the brain.


  • Alzheimer's typically occurs in people over the age of 65, but can occur at an earlier age. More research is needed to study the effects of aging on cognitive decline in the brain and its relationship to Alzheimer’s disease. 
  • Researchers have identified several genes that may play a role in the development of Alzheimer’s disease. One is identified as apolipoprotein E (APOE4), although genetic testing for APOE4 will not predict whether a person will develop Alzheimer’s disease. 
  • Everyone has the normal (also called wild type) APOE4 gene, but some people inherit one of many variants (also called alleles or mutations) of APOE4. Having an unusual form of APOE4 does not mean you will get Alzheimer’s disease,  and having normal APOE does not guarantee that you will remain clear of the disease.
  • Current research shows a link between cognitive decline and vascular and metabolic disorders, such as heart disease, hypertension, stroke, diabetes and obesity. More research is needed to better understand these relationships and to determine whether changing these risk factors can affect the development or progression of Alzheimer’s disease.

Stages of Alzheimer's Disease

Each patient with Alzheimer’s disease is unique, and their illness may progress at a different pace. The following stages are used to provide general information about how the disease tends to advance. Some characteristics of each stage of Alzheimer’s disease  may overlap.


Subtle behavior changes may occur in someone with Alzheimer's disease, such as forgetfulness or mood swings, before they are diagnosed with the disease.


Because Alzheimer’s disease is a disease that needs attention and care to maximize the ability to function and also may respond to treatment, the earlier you seek medical attention, the more Houston Methodist physicians can do to determine the cause of the symptoms — whether it is Alzheimer’s disease or some other cause.


Once an Alzheimer’s diagnosis is confirmed, Houston Methodist’s physicians can begin treatment that might slow the progression of the disease and provide the caregiver with much-needed help and support.


Alzheimer’s disease should not feel like a huge burden for either the patient or the caretaker. It is an illness just like any other that requires extensive, accurate medical attention. Our doctors have special training in memory loss and geriatrics to help determine the cause, develop a treatment plan and connect you to support that is helpful, and possibly necessary, for dealing with Alzheimer’s disease.

Mild cognitive impairment

Mild cognitive impairment (MCI) can be thought of as the stage between the normal cognitive decline of aging and serious decline of dementia.


During this stage, issues relating to memory, language and judgment are more severe than normal age-related changes, but not severe enough to restrict regular daily work or activities of daily living or to be diagnosed with early stage or mild Alzheimer’s disease.


People with MCI do have an increased risk of developing Alzheimer’s disease  or other types of dementia.

Early stage or mild Alzheimer’s disease

In the early or mild stage of Alzheimer's disease, patients continue experiencing problems with memory and thinking, and begin developing some or all of these additional cognitive issues:


  • Getting lost
  • Misplacing keys or other important items in unusual places
  • Having trouble handling money — balancing a checkbook or making change
  • Repeating questions without realizing it
  • Being unable to follow a recipe
  • Needing more time to complete normal daily tasks


People with mild Alzheimer’s disease might stop doing things that they have always enjoyed, such as playing cards, volunteering or leaving the house alone. This could be because they know that something is wrong and do not want others to see it. Alzheimer's-related changes in the brain may be altering their mood and personality.


Caring for someone diagnosed with any disease, even one not as challenging as Alzheimer’s disease, can take a toll on a caregiver, so it is important that you take care of yourself — physically, mentally and emotionally — and seek help from others from the beginning. This is also good for the loved one with Alzheimer’s disease.

Middle-stage or moderate Alzheimer’s disease

Patients with middle-stage or moderate Alzheimer's disease typically exhibit changes in behavior and increased memory problems, such that they need continuous attention.


These changes can be caused by environmental factors or disease progression. Some aspects of the environment can be simplified or otherwise adapted to the changing needs of the person with Alzheimer’s disease.


During this stage, the damage spreads to areas of the brain that control language, reasoning, sensory processing and conscious thought.


Patients may begin having problems recognizing family and friends and remembering their address, phone number, what day it is or where they are. They may also wander, possibly looking for a place that feels like home.


In persons with moderate Alzheimer's disease, confusion increases and the patient finds it harder to learn new things, cope with new situations and perform activities, such as getting dressed, which involve only a few familiar steps.


There is often a change in behavior late in the day (known as sundowning) when the person with Alzheimer’s disease  may become more suspicious, restless or agitated, especially in the evening hours.


Some characteristic behaviors can be thought of as common Alzheimer's-related behaviors at the moderate or middle stage of Alzheimer’s disease:


  • Telling the same story over and over
  • Using words or saying things that do not make sense
  • Arguing about taking a bath or medications
  • Making up stories to fill in gaps of memory
  • Mistaking one friend for another
  • Changing sleep patterns
  • Wandering around the house or trying to leave the house to go “home”
  • Acting aggressively or becoming agitated in the evening, also known as sundowning


Because these changes can be confusing and frustrating to the person with Alzheimer’s disease, as well as to the caregiver, it is important that you seek help and support for yourself and for your loved one.

Late-stage or severe Alzheimer’s disease

Persons with late-stage or severe Alzheimer's disease are completely dependent on caregivers for their care because plaques and tangles have spread throughout the brain, affecting movement, communication and often the ability to recognize family members and friends.


Patients with advanced Alzheimer’s disease  may lose memories of their own life events and become anxious or frightened.


Physical inactivity can result in loss of fitness (muscle tone) and cause muscles to atrophy, resulting in the inability to walk with or without a cane or other assistive device or sit up in a chair.


Certain characteristic behaviors can be thought of as common Alzheimer's-related behaviors during severe or late-stage Alzheimer’s disease:


  • Inability to speak coherently
  • Inability to dress, get out of bed, bathe or use the bathroom without assistance
  • Impaired swallowing 
  • Loss of bladder control


Additional information is available to help you learn more about Alzheimer’s disease:


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