Abstract
Background
Olfactory episodic memory (OEM) could provide more valuable diagnostic information for the detection of Alzheimer's Disease than either olfactory identification or episodic memory alone (Croy et al., 2015; Murphy, Nordin & Acosta, 1997). However, very few validated tests of OEM are available which assess learning and memory characteristics. The present study aims to validate a newly developed Western Australia Olfactory Memory Test (WAOMT) in older adults which measures learning and memory characteristics of OEM.
Methods
A final sample of 181 participants were recruited from the Western Australia Memory Study (WAMS). Nine target odours were presented over 3 learning trials and participants named as many odours at the end of each trial, followed by a distractor list, short-delay free recall (SDFR) and short-delay cued recall. Long-delay free (LDFR) and cued recall (LDCR), and recognition (Y/N) was administered after a 20 minute delay. A liberal scoring criteria was used. Convergent validity was examined between OEM and conceptually similar constructs of verbal and visual episodic memory, and odour identification. Divergent validity was examined between executive functioning and visual-spatial abilities. Test re-test reliability was examined with 12 participants between 7 to 28 days.
Results
Test re-test reliability was adequate for learning trials, LDFR & d’ (r=.67 to .73; p<.05). Analysis revealed significant inter-correlations between learning and memory scores (r=.33 to .93), components of WAOMT and odour identification (r=.15 to .21), verbal episodic memory (r =.17 to .26) and visual episodic memory (r = .16 to .27). Females performed better than males on Trial 3 F(1,113) = 4.49, p = .4 and recognition hits F(1,113) = 6.24, p = .14, controlling for MoCA scores. Performance decreased with age (r = -.13 to -.20).
Conclusions
Relationships were found between conceptually similar constructs of verbal and visual episodic memory and odour identification. Performance was found to decrease with age, and females demonstrated an advantage overall males in learning trial 3 and recognition hits. The WAOMT presents a reliable, valid and simple test of odour episodic memory. Future research implications include examining the longitudinal relationship between OEM and cognitive decline.