Alzheimer’s disease (AD) is an irreversible and progressive neurological disorder, and the most common type of dementia. It is caused by damage to the brain and often first appears as minor changes in behavior and problems with memory. However, the range and severity of the symptoms increase with time as the damage to the brain spreads.

Its progression is categorized into three broad stages: mild (early), moderate (middle) and severe (late). As the disease advances, patients become less and less independent and, by late stages, generally need a high level of constant care. These stages are generally used only as a guideline, as the symptoms develop differently in each patient. Symptoms may overlap or not occur at all, so it may be difficult to accurately stage the disease.

Patients with early-onset AD (younger than 65) are often diagnosed much later, as their symptoms can manifest in different ways and can progress faster, making the disease more difficult to classify.

Preclinical AD

Prior to the start of the symptoms, a patient is said to be in the preclinical stage. This stage refers to the time after the brain has started to accumulate damage, but before enough damage has occurred to cause noticeable symptoms. Researchers are working to develop new diagnostic techniques that may be able to identify AD at a preclinical stage, such as identifying new biomarkers (a measure to indicate if there is an increased risk of the disease) or brain scanning techniques that might spot AD-specific forms of damage (amyloid plaques).

Mild (early stage) AD

In its early stages, the symptoms of Alzheimer’s are generally not severe enough to affect work or relationships, but they may be having an impact on daily life in general. At this stage, the patient may experience memory problems (such as not recalling recent events or misplacing items), difficulty learning new things, and be experiencing mood swings (depression, anxiety, irritability, apathy, and/or confusion), and difficulties making decisions.

Moderate (middle stage) AD

As the disease progresses, the patient’s memory problems increase in severity. People with moderate Alzheimer’s may have difficulty remembering their personal history, locations of known places, people, and time of day or the season. These memory gaps can increase the confusion and disorientation a patient experiences. He or she may also start experiencing hallucinations (seeing things that are not there) or delusions (believing things that are not true), which can lead to paranoia, suspicion, and aggressive behavior. In this stage, the patient requires a greater level of care and attention to complete day-to-day activities.

Severe (late stage) AD

In the later stages of Alzheimer’s, the patient may need full-time care and assistance in carrying out essential tasks such as eating, moving, dressing, and using the bathroom. People at this stage can also be more vulnerable to infections and pneumonia, and, as they find it increasingly difficult to communicate, they may be unable to convey this to a carer. They also have markedly lower physical capabilities, and may not be able to walk or sit unaided and may experience difficulty in swallowing.

Note: Alzheimer’s News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.