Longitudinal Study of the Transition From Healthy Aging to Alzheimer Disease

Abstract

Recent studies have focused on identifying the beginning of the transition from healthy aging to dementia. As new interventions become available, it will become important to identify the disease as early as possible. A piecewise regression analysis of a measure of episodic memory identified an inflection point 5 years before diagnosis in the Bronx Aging Study.¹ A flat trajectory followed by decline beginning 7 years before diagnosis of dementia was reported for the same measure in the Baltimore Longitudinal Study of Aging,² which also found decline in executive function that increased in rate 2 to 3 years before diagnosis. Episodic memory is not the only aspect of cognition that can be affected in preclinical Alzheimer disease (AD).³ Indeed, mild cognitive impairment, often thought to represent a transitional state between healthy cognitive aging and AD, is defined on the basis of deficits in cognitive domains in addition to memory.⁴