An investigation of dementia among elderly outpatients.

A total of 110 unselected demented outpatients aged 60 and over (mean age: 76.2 years), 69 women and 41 men, were prospectively investigated. A potentially reversible cause of dementia was found in 26 patients (normal pressure hydrocephalus 2, cerebral tumor 1, hyperthyroidism 2, hypothyroidism 4, vitamin B12 deficiency 13, pseudodementia 4). Follow-up investigation showed that the only true reversible dementia in which improvement from abnormal to normal mental status occurred and was sustained for up to 2 years was 1 case of normal pressure hydrocephalus and 1 case of pseudodementia. In all cases of vitamin B12 deficiency, hypothyroidism and hyperthyroidism, despite proper treatment, mental status did not improve significantly and follow-up in most cases showed persistant cognitive deterioration. It can be concluded that although true reversible dementias do exist, they do not seem as prevalent as previously reported. Most elderly outpatients with reversible causes of dementia do not revert to normal and continue showing progressive decline.