Objective: Technological developments during the past decade have led to a greater understanding of brain function and genetic risk in Alzheimer’s disease, particularly early in the disease course. For assessing dementia or age-related memory complaints, functional imaging – particularly positron emission tomography (PET) scanning because of the biological information it provides – offers the advantage of providing a positive diagnosis of early Alzheimer’s disease often before clinicians can identify the condition using conventional clinical assessments. In addition, evidence is accumulating that nonpharmacological interventions and lifelong habits may decelerate brain aging.
Design: Review of recent cross-sectional and longitudinal clinical studies including brain imaging and genetic risk measures is done. Medline review of Alzheimer's disease epidemiological studies of environmental risks and protective factors.
Materials and Methods: Human studies, peer-reviewed publications.
Results: Longitudinal clinical and autopsy studies have shown that PET provides greater diagnostic accuracy than standard clinical assessment methods. The characteristic parietal and temporal deficits observed on a PET scan can be recognized years prior to clinical confirmation, particularly when combined with genetic risk measures (apolipoprotein E-4 [APOE-4]). Most of the studies have used PET to measure regional glucose metabolism, which reflects neuronal activity. More recently, methods have been developed for PET to provide measures reflecting the concentration of amyloid plaques and neurofibrillary tangles. For people with mild forms of age-related memory loss, the body of evidence points to diet, physical exercise, avoidance of head trauma, and other lifestyle choices that may protect the brain from future decline.
Conclusion: PET scan measures of regional glucose metabolism may assist in the early diagnosis of dementia and combining them with genetic risk information may offer a tool for monitoring anti-dementia treatments. PET measures of plaque and tangle burden may prove useful in providing surrogate markers for treatments designed to prevent or eliminate brain amyloid burden. Although definitive proof of the value of lifestyle changes to prevent dementia is not yet available, the risks are minimal and are not likely to outweigh the potential benefits.
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