One major difference: dementia doesn’t go away, but delirium does — that is, when the underlying cause is properly treated. It gets complicated though, because the erratic, paranoid, and sometimes frightening behaviors associated with delirium can be quite similar to those associated with dementia. However, a dramatic, seemingly overnight spike in these types of behaviors is probably a good indication that the person is suffering from an undiagnosed illness, such as pneumonia or a urinary tract infection (UTI). These illnesses, which are common among seniors, can provoke symptoms of delirium. Other causes of delirium include medication side effects, alcohol or drug abuse, or the ingestion of poison; post-surgery, many people also experience delirium.
Though delirium typically affects those who have been hospitalized or reside in assisted living/other senior care communities, an at home caregiver should still be aware of the symptoms and triggers. Generally, delirium appears in a few hours or a few days. Sometimes, dementia symptoms can appear overnight, but the decline is typically a gradual one, not like the suddenness of delirium.