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An olfactory 'stress test' may detect preclinical Alzheimer's disease.

Schofield PW, Ebrahimi H, Jones AL, Bateman GA, Murray SR - BMC Neurol (2012)

Bottom Line: In a convenience sample of 56 elderly individuals (14 probable AD, 13 cognitive impairment no dementia, 29 cognitively intact) the change in UPSIT score after atropine ('atropine effect' = AE) correlated significantly with demographically scaled episodic memory score (r = 0.57, p < 0.001) and left hippocampal volume (LHCV) (r = 0.53, p < 0.001).The presence of any APOE ϵ4 allele was associated with a more negative AE (p = 0.014).The OST using atropine as an olfactory probe holds promise as a simple, inexpensive screen for early and preclinical AD and further work, including longitudinal studies, is needed to explore this possibility.

View Article: PubMed Central - HTML - PubMed

Affiliation: Neuropsychiatry service, Hunter New England Area Health, Newcastle, Australia. peter.schofield@hnehealth.nsw.gov.au

ABSTRACT

Background: The olfactory bulb (OB) receives extensive cholinergic input from the basal forebrain and is affected very early in Alzheimer's disease (AD). We speculated that an olfactory 'stress test' (OST), targeting the OB, might be used to unmask incipient AD. We investigated if change in olfactory performance following intranasal atropine was associated with several known antecedents or biomarkers of AD.

Methods: We measured change in performance on the University of Pennsylvania Smell Identification Test (UPSIT) in the left nostril before (20-items) and after (remaining 20-items) intranasal administration of 1 mg of atropine. We administered cognitive tests, measured hippocampal volume from MRI scans and recorded Apolipoprotein E genotype as indices relevant to underlying AD.

Results: In a convenience sample of 56 elderly individuals (14 probable AD, 13 cognitive impairment no dementia, 29 cognitively intact) the change in UPSIT score after atropine ('atropine effect' = AE) correlated significantly with demographically scaled episodic memory score (r = 0.57, p < 0.001) and left hippocampal volume (LHCV) (r = 0.53, p < 0.001). Among non-demented individuals (n = 42), AE correlated with episodic memory (r = 0.52, p < 0.001) and LHCV (r = 0.49, p < 0.001) and hierarchical linear regression models adjusted for age, gender, education, and baseline UPSIT showed that the AE explained more variance in memory performance (24%) than did LHCV (15%). The presence of any APOE ϵ4 allele was associated with a more negative AE (p = 0.014).

Conclusions: The OST using atropine as an olfactory probe holds promise as a simple, inexpensive screen for early and preclinical AD and further work, including longitudinal studies, is needed to explore this possibility.

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Related in: MedlinePlus

Atropine effect vs. left hippocampal volume. A strong relationship exists between atropine effect and hippocampal volume (r = 0.53, P = 0.0001) with more negative scores on AE associated with more atrophic hippocampi.
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Figure 3: Atropine effect vs. left hippocampal volume. A strong relationship exists between atropine effect and hippocampal volume (r = 0.53, P = 0.0001) with more negative scores on AE associated with more atrophic hippocampi.

Mentions: AE ranged from +5 to −6. Figure 1 depicts the distribution of AE by cognitive category. AE < 0 was present in 31% NC, 92% with CI and 86% with AD. Figure 2 shows the scatter plot of AE against scaled memory score. Figure 3 shows the scatter plot of AE and LHCV.


An olfactory 'stress test' may detect preclinical Alzheimer's disease.

Schofield PW, Ebrahimi H, Jones AL, Bateman GA, Murray SR - BMC Neurol (2012)

Atropine effect vs. left hippocampal volume. A strong relationship exists between atropine effect and hippocampal volume (r = 0.53, P = 0.0001) with more negative scores on AE associated with more atrophic hippocampi.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3403955&req=5

Figure 3: Atropine effect vs. left hippocampal volume. A strong relationship exists between atropine effect and hippocampal volume (r = 0.53, P = 0.0001) with more negative scores on AE associated with more atrophic hippocampi.
Mentions: AE ranged from +5 to −6. Figure 1 depicts the distribution of AE by cognitive category. AE < 0 was present in 31% NC, 92% with CI and 86% with AD. Figure 2 shows the scatter plot of AE against scaled memory score. Figure 3 shows the scatter plot of AE and LHCV.

Bottom Line: In a convenience sample of 56 elderly individuals (14 probable AD, 13 cognitive impairment no dementia, 29 cognitively intact) the change in UPSIT score after atropine ('atropine effect' = AE) correlated significantly with demographically scaled episodic memory score (r = 0.57, p < 0.001) and left hippocampal volume (LHCV) (r = 0.53, p < 0.001).The presence of any APOE ϵ4 allele was associated with a more negative AE (p = 0.014).The OST using atropine as an olfactory probe holds promise as a simple, inexpensive screen for early and preclinical AD and further work, including longitudinal studies, is needed to explore this possibility.

View Article: PubMed Central - HTML - PubMed

Affiliation: Neuropsychiatry service, Hunter New England Area Health, Newcastle, Australia. peter.schofield@hnehealth.nsw.gov.au

ABSTRACT

Background: The olfactory bulb (OB) receives extensive cholinergic input from the basal forebrain and is affected very early in Alzheimer's disease (AD). We speculated that an olfactory 'stress test' (OST), targeting the OB, might be used to unmask incipient AD. We investigated if change in olfactory performance following intranasal atropine was associated with several known antecedents or biomarkers of AD.

Methods: We measured change in performance on the University of Pennsylvania Smell Identification Test (UPSIT) in the left nostril before (20-items) and after (remaining 20-items) intranasal administration of 1 mg of atropine. We administered cognitive tests, measured hippocampal volume from MRI scans and recorded Apolipoprotein E genotype as indices relevant to underlying AD.

Results: In a convenience sample of 56 elderly individuals (14 probable AD, 13 cognitive impairment no dementia, 29 cognitively intact) the change in UPSIT score after atropine ('atropine effect' = AE) correlated significantly with demographically scaled episodic memory score (r = 0.57, p < 0.001) and left hippocampal volume (LHCV) (r = 0.53, p < 0.001). Among non-demented individuals (n = 42), AE correlated with episodic memory (r = 0.52, p < 0.001) and LHCV (r = 0.49, p < 0.001) and hierarchical linear regression models adjusted for age, gender, education, and baseline UPSIT showed that the AE explained more variance in memory performance (24%) than did LHCV (15%). The presence of any APOE ϵ4 allele was associated with a more negative AE (p = 0.014).

Conclusions: The OST using atropine as an olfactory probe holds promise as a simple, inexpensive screen for early and preclinical AD and further work, including longitudinal studies, is needed to explore this possibility.

Show MeSH
Related in: MedlinePlus