Longitudinal changes in odor identification performance and neuropsychological measures in aging individuals

To examine changes in odor identification performance and cognitive measures in healthy aging individuals. While cross-sectional studies reveal associations between odor identification and measures of episodic memory, processing speed, and executive function, longitudinal studies so far have been ambiguous with regard to demonstrating that odor identification may be predictive of decline in cognitive function.

One hundred and 7 healthy aging individuals (average age 60.2 years, 71% women) were assessed with an odor identification test and nonolfactory cognitive measures of verbal episodic memory, mental processing speed, executive function, and language 3 times, covering a period of 6.5 years.

The cross-sectional results revealed odor identification performance to be associated with age, measures of verbal episodic memory, and processing speed. Using linear mixed models, the longitudinal analyses revealed age-associated decline in all measures. Controlling for retest effects, the analyses demonstrated that gender was a significant predictor for episodic memory and mental processing speed. Odor identification performance was further shown to be a significant predictor for episodic verbal memory.

This study shows age-related decline in odor identification as well as nonolfactory cognitive measures. The finding showing that odor identification is a significant predictor for verbal episodic memory is of great clinical interest as odor identification has been suggested as a sensitive measure of incipient pathologic cognitive decline.