A novel approach to assessing memory at the population level: vulnerability to semantic interference.

BACKGROUND: There is increasing interest in identifying novel cognitive paradigms to help detect preclinical dementia. Promising results have been found in clinical settings using the Semantic Interference Test (SIT), a modification of an existing episodic memory test (Fuld Object Memory Evaluation) that exploits vulnerability to semantic interference in Alzheimer's disease. It is not yet known how broadly this work will generalize to the community at large.
METHODS: Participants aged > or = 65 years from the Monongahela-Youghiogheny Healthy Aging Team (MYHAT) were administered the SIT at study entry. Independent of neuropsychological assessment, participants were rated on the Clinical Dementia Rating (CDR) scale, based on reported loss of cognitively driven everyday functioning. In individuals free of dementia (CDR < 1), the concurrent validity of the SIT was assessed by determining its association with CDR using multiple logistic regression models, with CDR 0 (no dementia) vs. 0.5 (possible dementia) as the outcome and the SIT test variables as predictors.
RESULTS: Poorer performance on all SIT variables but one was associated with higher CDR reflecting possible dementia (Odds Ratios 2.24-4.79). Younger age and female gender also conferred a performance advantage. Years of education and reading ability (a proxy for quality of education) evidenced a very weak association with SIT performance.
CONCLUSIONS: The SIT shows promise as a valid, novel measure to identify early preclinical dementia in a community setting. It has potential utility for assessment of persons who may be illiterate or of low education. Finally, we provide normative SIT data stratified by age which may be utilized by clinicians or researchers in future investigations.