Amnesia refers to memory loss and is often the most easily visible and common sign of Alzheimer's disease. Memory loss in Alzheimer's disease typically begins with short-term memory and progresses to a decline in long-term memory.1
- Retrograde amnesia is memory loss that is limited to the period before a head injury occurred or before a disease such as Alzheimer's developed. Retrograde amnesia hinders the ability to retrieve the memories that were already stored in the brain.
- Anterograde amnesia is memory loss that is present for events that occur or information that is presented after a brain injury or disease develops. The ability to make new memories is impaired in anterograde amnesia.
Aphasia is a term used to describe impaired communication. Aphasia may be classified as expressive aphasia, where someone is unable to find the right words or may say them incorrectly, or receptive aphasia, where the ability to understand, receive and interpret language is impaired.
Apraxia is a deficit in voluntary motor skills. While Alzheimer's is known primarily for affecting cognitive functioning, it also affects the body's physical ability to function. As Alzheimer's progresses, the ability to perform certain activities of daily living such as bathing and getting dressed might decline. Activities such as walking and eating become more difficult in the late stages of Alzheimer's disease.4
Due to these changes, people living with Alzheimer's also are at a high risk of falling, and when they do fall, they are at a higher risk of fracturing their hip. Remaining as active as possible, for as long as possible, may help delay some of the physical changes in apraxia that develop in Alzheimer's.5
Agnosia is the impairment of the ability to receive or correctly understand information from the senses of hearing, smell, taste, touch, and vision. For example, people with Alzheimer's disease often are less able to identify smells or understand the feeling of a full bladder. They also might not be able to recognize loved ones6 as the disease progresses. Difficulty recognizing or interpreting visual shapes is frequently present in Alzheimer's disease.
Agnosia may also be auditory, where the sense of hearing is intact but the ability to interpret what the sound means is impaired.
The presence of agnosia is often part of a cognitive assessment. For example, one task on the mini-mental state exam (MMSE) requires the test-taker to copy an intersecting pentagon figure. Difficulty in this task reduces the total points the person achieves on this test and can be a sign of cognitive impairment.
A Word From Verywell
Alzheimer's disease has many symptoms which can be loosely grouped into these four categories. If you recognize these symptoms in someone you love, make sure to contact the physician for a full evaluation. While the impairments may be due to Alzheimer's disease, there are also other conditions that may cause these symptoms, some of which may be reversible if identified and treated. Thus, early identification and assessment are necessary and beneficial.