Mild cognitive impairment (MCI) and dementia exist on a continuum, with MCI representing a stage between expected cognitive decline of normal aging and more serious decline associated with dementia. MCI is characterized by memory impairment greater than normal aging but not significantly interfering with daily life, while dementia involves memory and other cognitive impairments that do interfere with daily functioning. Only a small percentage of dementias are potentially reversible through treatment of underlying causes.