Dementia is a progressive deterioration of intellect, behavior and personality caused by diseases of the brain. The most common causes are Alzheimer's disease (~60% of cases) and cerebrovascular disease (~20% of cases). Dementia is not a single disease but an overall term for loss of brain function. Treatment depends on the underlying cause but currently available medications can only temporarily improve symptoms and do not cure or slow progression. Lifestyle factors may help reduce risk of conditions that can lead to dementia like stroke.