ing. A recent larger study from the same longitudinal studies found that faster rates of cognitive decline were associated with AD pathology, macroscopic infarcts, and neocortical Lewy bodies, but the combination of all of these pathologies explained only 41% of the variation in rate of decline in this sample of older adults without dementia. 29 Thus, these late-life diseases cause an acceleration of cognitive decline that results in the development of dementia in many patients, but some older adults without dementia do have cognitive decline not caused by these pathologic changes. AD is the most common cause of cognitive decline in older adults. The prevalence of clinically diagnosed AD increases exponentially with age. At age 65, less than 5% of the population has a clinical diagnosis of AD, but this number increases to more than 40% beyond age 85. 2 30 For patients who develop AD, most first demonstrate a subtle decline in memory and new learning, followed by mild changes in executive cognitive function and later changes in language and visuospatial processing. Many of these changes in cognition are similar to normal cognitive aging changes, but differ by severity. 31 32 The onset of cognitive decline is subtle and hard to determine. Progression is gradual and may be more apparent to family members than the patient. Clinically, most patients first develop mild cognitive impairment (MCI), which is defined as a syndrome of cognitive complaints, measureable mild declines in cognition, but no change in functional abilities, including instrumental activities of daily living. MCI can involve one or more cognitive domains, but memory domain-only MCI (i.e., amnestic MCI) is seen most commonly in patients who go on to develop AD. If cognitive impairments continue to progress and the patient develops evidence of functional impairment caused by these cognitive impairments, then he or she would be diagnosed as having dementia. If the patient meets the clinical criteria for A