Normal aging, mild cognitive impairment, and early Alzheimer's disease

BACKGROUND- Some cognitive changes occur as a function of normal aging. Consequently, the distinction between normal aging and early demential can present a difficult problem for the clinician. In addition, there is likely a transitional phase of a mild cognitive impairment through which some individuals evolve in developing dementia. REVIEW SUMMARY- To address these issues, this review discusses cognitive changes in normal aging and early dementia and describes the condition of a mild cognitive impairment. In normal aging, learning or acquisition performance declines gradually, whereas recall of information after a delay is relatively preserved. However, in early dementias, such as Alzheimer's disease, learning performance declines dramatically and delayed recall is also impaired significantly. Other functions such as cognitive flexibility and speed of mental processing may also decline in normal aging. It seems that the condition of a mild cognitive impairment can be defined and the natural history of these individuals is known. In addition, predictor variables of the ultimate outcome have been characterized. CONCLUSION- The transition from normal aging through mild cognitive impairment ultimately to dementia can be delineated. As therapeutic agents become available, it becomes increasingly important to be able to characterize individuals along this continuum to allow for early intervention.