Early Functional Limitations in Cognitively Normal Older Adults Predict Diagnostic Conversion to Mild Cognitive Impairment

Objectives: To examine whether specific types of early functional limitations in cognitively normal older adults are associated with subsequent development of mild cognitive impairment (MCI), as well as the relative predictive value of self versus informant report in predicting diagnostic conversion to MCI. Design: As a part of a longitudinal study design, participants underwent baseline and annual multidisciplinary clinical evaluations, including a physical and neurological examination, imaging, laboratory work, and neuropsychological testing. Setting: Data used in this study were collected as part of longitudinal research at the University of California, Davis Alzheimer's Disease Center. Participants: Individuals diagnosed as having normal cognition at study baseline who had an informant who could complete informant-based ratings and at least one follow-up visit (N = 324). Measurements: Participants and informants each completed the Everyday Cognition Scale (ECog), an instrument designed to measure everyday function in six cognitively relevant domains. Results: Self- and informant-reported functional limitations on the ECog were associated with significantly greater risk of diagnostic conversion to MCI (informant: hazard ratio (HR) = 2.0, 95% confidence interval (CI) = 1.3-3.2, P = .002), with self-report having a slightly higher hazard (HR = 2.3, 95% CI = 1.4-3.6, P < .001). When controlling for baseline cognitive abilities, the effect remained significant for self- and informant-reported functional limitations. Conclusion: Deficits in everyday memory and executive function domains were the strongest predictors of diagnostic conversion to MCI. Detection of early functional limitations may be clinically useful in assessing the future risk of developing cognitive impairment in cognitively normal older adults.