Dementia is a long-term disease. It has a range of symptoms that mean a person's brain is losing function. A person's ability to think, remember, and communicate gets worse over time. These changes are permanent. This process occurs over months to years. It can happen quickly or slowly. This depends on the cause.
At first, a person may sometimes be forgetful or confused. Symptoms may be mild. As the condition gets worse, the person will repeat questions. They may forget basic information. Over time, they'll have trouble following directions and doing daily tasks. They'll have trouble talking with and understanding people. They may forget who people are. They may not know where they are. They may also be moody or restless.
In some cases, dementia can occur suddenly. For example, a stroke or head injury can cause permanent trouble with thinking and communication. In these cases, dementia may not get worse with time.
People with dementia are at risk of also having delirium. This means a person with dementia may have worse symptoms due to another health problem. When the health problem is treated, the symptoms may improve. But the person will still have dementia.