Clinicians generally divide Alzheimer's disease into three stages: mild, moderate and severe, although the symptoms of each stage often overlap, explains the Alzheimer's Association. Independent functioning may still be possible in early-stage Alzheimer's, whereas late-stage Alzheimer's is marked by an inability to interact with one's environment.
In mild Alzheimer's, a person is apt to still drive, work and interact socially, according to the Alzheimer's Association. The patient may have lapses in memory, such as forgetting where something is placed or familiar words. This early stage of the disease is noticeable by difficulty remembering names shortly after being introduced to someone, increasing problems planning and organizing, challenges thinking of the correct name or word, and forgetfulness about material just read.
As the longest stage of the disease, moderate Alzheimer's can last many years. An outsider may observe the person becoming more irritable, mixing up language or behaving in uncharacteristic ways, according to the Alzheimer's Association. Someone at this point may become moody or withdrawn, particularly when in social situations. There may be confusion about what day it is, with changes in sleep patterns. During this time, a person is likely to wander and become lost with an inability to recall personal details, such as phone numbers and addresses.
Severe Alzheimer's necessitates full-time care, as a person becomes unable to move or participate in conversation. Personality changes are common in this stage as a person forgets recent experiences and previously known associates. Someone with late-stage Alzheimer's is especially vulnerable to infections, most notably pneumonia, the Alzheimer's Association states.