Delirium is an acute confusional state that can be mistaken for dementia, or the onset of dementia, as it often presents similar symptoms. Typically these are disruptions in thinking and behaviour that frequently manifest themselves as changes in perception, sudden and inexplicable changes in mood, increased agitation and an inability to concentrate or pay attention, and a significantly reduced level of activity. However, typical delirium presents rapidly (over days or weeks) and is usually reversible, as opposed to dementia, which normally develops more slowly, frequently over months and years, and is incurable. Possible causes of delirium include stroke, urinary tract or chest infection, influenza, diarrhoea, dehydration, or any other acute medical illness. Triggers may also include anaemia, pain, immobilization after surgery, abrupt cessation of medication or alcohol use. Unfortunately, dementia itself is also a cause of delirium.