Influence of Cognitive Status, Age, and APOE-4 Genetic Risk on Brain FDDNP Positron-Emission Tomography Imaging in Persons Without Dementia

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Abstract
Neurodegeneration associated with aging progresses along a continuum,1 but it has been categorized according to the degree of cognitive impairment. In normal aging, mild memory concerns with minimal objective cognitive deficits have been observed in nearly half of people by 50 years of age.2 Such awareness of memory changes is usually stable and not a risk factor for future cognitive decline.3 Mild cognitive impairment (MCI) is a more advanced form of age-related cognitive decline in which people notice memory changes and neuropsychological tests often confirm problems with delayed recall, although non–memory-related cognitive domains may also be impaired.4 People experiencing this transitional state between normal aging and dementia are still able to live independently, but they have an increased risk for developing dementia. A recent study that followed patients with MCI for 30 months reported conversion rates to Alzheimer disease (AD) ranging from 27% to 49%, depending on the subtype of MCI.5 The prevalence of MCI may be as high as 19% in people older than 65 years and 29% in those older than 85 years.6 When cognitive decline interferes with daily functioning and impairs not just memory but other mental abilities, dementia is often diagnosed.7 Alzheimer disease, which accounts for most cases, is insidious in its onset and progressive in its course.8 The prevalence of AD in individuals aged 71 years and older approaches 10%,9 and by 85 years has been reported to be as high as 50%.10