Dementia is a syndrome, thus there are many ‘types’ of dementia. Not all dementias worsen. Sometimes dementia (the loss of cognitive function) occurs as the result of a single event (e.g., temporary hypoxia, or loss of oxygen supply to the brain, as in a choking accident) and reverses over time or with rehabilitative exercises. Other times it remains stable. Sometimes, it is caused by vitamin deficiencies (e.g., B12, thiamine), hormonal abnormalities (e.g., hypothyroidism, hypogonadism), an unrecognized seizure disorder, infection (e.g., HIV, Lyme, syphilis), or sleep disorder (e.g., apnea) and may be stabilized or even reversed (e.g. normal pressure hydrocephalus). Because of the potential to be reversed, once it is noticed, it should be thoroughly evaluated immediately.
Other dementias are rapidly progressive (e.g., Creutzfeldt Jacob disease, tumors, liver failure). Many dementias are slowly progressive over the course of years (e.g., Alzheimer’s, Fronto-temporal Dementia, Parkinson’s).