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Olfaction, the ‘Olfactory Stress Test’ and correlates in a sample of elders
Author(s) -
Bukajumbe Emmanuel,
Attia John,
McEvoy Mark,
Jones Alison L,
Schofield Peter W.
Publication year - 2020
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1002/alz.046013
Subject(s) - olfaction , boston naming test , audiology , cognition , hyposmia , atropine , psychology , cognitive test , dementia , hippocampal formation , medicine , clinical psychology , psychiatry , neuroscience , neuropsychology , disease , covid-19 , infectious disease (medical specialty)
Background Previously, we investigated the potential of an atropine challenge procedure (‘the Olfactory Stress Test’ (OST)) to detect early AD. Olfaction was tested with 20 items of the University of Pennsylvania Smell Identification test (UPSIT)) before, and with the remaining 20 items after, a unilateral intranasal spray of atropine. In that small study of individuals with normal cognition, cognitive impairment and probable AD, the change in olfaction after atropine (the ‘atropine effect’ (AE)) was significantly correlated with cognition, hippocampal volume and ApoE‐ε4 allele status. In the present study, we administered the OST to a larger sample of mainly cognitively normal elders. Method 295 community‐dwelling elders (mean age of 72.63, SD=5.81 years) underwent olfactory testing as described above. Participants were administered the Audio Recorded Cognitive Screen (ARCS)), the Hyposmia Rating Scale (HRS), were genotyped for APOE, and a subsample underwent brain MRI. Linear regression analyses were undertaken seeking associations of olfactory measures, or the HRS, with cognition, hippocampal volume and APOE genotype. Result Mean post atropine UPSIT scores were lower than pre‐atropine UPSIT scores (‘preup’) (Student’s paired t‐test = 9.155, p<0.001). After controlling for sociodemographic and health factors, preup and AE were associated with ARCS (β=1.225 (0.621 – 1.889, p<0.001) and β = ‐0.598 (‐8.731 – ‐0.172, p=0.095)), respectively. Compared to preup scores ≥15, scores <15 were associated with a mean ARCS less by 6.509 (β = ‐6.509 (‐10.805 – ‐2.212, p=0.003)). Using a dichotomised AE, AE≥0 was associated with mean ARCS score less than AE<0 by 4.452 (β = ‐4.452 (‐8.731 – ‐0.172, p=0.042)). Preup (but not AE or HRS) was associated with hippocampal volume. HRS was negatively associated with ARCS (β = ‐0.672 (‐1.238 – ‐0.106, p=0.020)). None of the predictors were associated with APOE genotype. Conclusion This study confirms previously reported associations of conventional olfaction tests with cognition. By contrast with our previous study, olfactory score change after atropine was more weakly, and negatively, associated with cognition. The current study failed to replicate our previous findings.