Background: Administration of cognitive test batteries by telephone has been shown to be a valid and cost-effective means of assessing cognition, but it remains relatively uncommon in epidemiological research.
Objectives: To develop composite cognitive measures and assess how much of the variability in their scores is associated with mode of test administration (ie, in person or by telephone).
Design: Cross-sectional cohort study.
Setting: Late-Onset Alzheimer's Disease Family Study conducted at 18 centers across the United States.
Participants: A total of 1584 persons, 368 with dementia, from 646 families.
Main outcome measures: Scores on composite measures of memory and cognitive function derived from a battery of 7 performance tests administered in person (69%) or by telephone (31%) by examiners who underwent a structured performance-based training program with annual recertification.
Results: Based in part on the results of a factor analysis of the 7 tests, we developed summary measures of working memory, declarative memory, episodic memory, semantic memory, and global cognition. In linear regression analyses, mode of test administration accounted for less than 2% of the variance in the measures. In mixed-effects models, variability in cognitive scores due to center was small relative to variability due to differences between individuals and families.
Conclusions: In epidemiologic research on aging and Alzheimer disease, assessment of cognition by telephone has little effect on performance and provides operational flexibility and a means of reducing both costs and missing data.