The vast majority of dementias fall under dementia of the Alzheimer’s Type (DAT), or Alzheimer’s Dementia (AD). Research has consistently shown that 10% of all individuals age 65 and older have AD, with AD occurring in as many as 47% of those who are over age 85. Age is clearly a predictive factor for the onset of Alzheimer’s disease. While normal aging can result in decline in cognitive function, the severity and progression of cognitive and functional impairment secondary to AD is far more dramatic, and physical studies of the brain show it to be caused by the disease process.
Alzheimer’s disease is a progressive neurological deterioration of the brain as opposed to Vascular dementia in which the deterioration of the brain is a secondary result to impaired circulation. Dementias are categorized as nonreversible, reversible, and static.
Alzheimer’s disease is the most common of the nonreversible dementias accounting for 60%. There are some reversible (treatable) dementias; however, taken together they constitute a much smaller percentage (25%). The static dementias (those that are alcohol, head injury, or stroke induced) account for the remaining 10%.
Depression is the most dramatic of the reversible dementias. Perhaps 10% of individuals present with depressive symptoms that are so profound they are sometimes diagnosed as having a pseudo dementia because their behavioral symptoms mimic Alzheimer’s disease so well. Given the effectiveness of the current medications, as many as 85% of depression can be controlled, if not cured. Thus the complicating factor of depression is significant enough to warrant its inclusion to screening procedures used with older individuals who exhibit cognitive decline.