One of the most alarming symptoms for people with dementia is that they have trouble understanding what is going on. At first, it is easy to dismiss the problem, and many people do. In such cases, they might blame the newspaper fonts for being too small, or the television programs for being too complicated, or the lights for being too dim to read properly, or family members being too interruptive. Sometimes this is straightforward denial, and sometimes it is a sign Sign
In medicine a sign is what a physician finds by examining a patient. For example, a patient with the symptom of pain might have signs of a fast heart rate, a pale face, a clammy touch and tenderness. of their dementia that they lack insight into what they can and cannot do. (The opposite problem is seen too, but much less often - e.g., the person believes that they cannot of what they can do. This can be seen with depression Depression
A disorder where a person experiences a constant state of sadness and low mood which interferes with their daily activity. (with or without dementia) and in frontotemporal dementia Frontotemporal dementia
A type of dementia that mainly affects the frontal lobe causing a problem in executive function tasks..

As it becomes clear that the problem is with them, people commonly seek treatment. They also adapt. Sometimes they are aware of this and sometimes not. Sometimes when they are not aware, a family member might notice that they have stopped doing more complex activities that required following a line of thought (such as reading or watching some plays and movies).

Another way that this becomes clear is when the person you care for frequently asks for an explanation of what has been seen, heard or read.

Disorders of comprehension and understanding often point to problems of language. They are seen with all the dementias, but especially Alzheimer's disease Alzheimer's disease
A neurological disease that affects memory and behaviour. It is characterized by beta-amyloid plaques and neurofibrillary tangles in the brain. There is no known cause but genetics and lifestyle are thought to play a role., some types of stroke Stroke

Blood supply to the brain is interrupted, usually by a blood clot. As a result, a portion of the brain can die from not receiving enough blood and oxygen.