Performance on an Alzheimer-selective odor identification test in patients with Parkinson's disease and its relationship with cerebral dopamine transporter activity
Received 15 January 2009; received in revised form 16 February 2009; accepted 12 March 2009.
Abstract
Background
Previous studies have shown selective deficits of odor identification in both Parkinson's disease (PD) and Alzheimer's disease (AD). Brief, selective AD smell screening tests have been developed to identify subjects at risk of AD. The disease specificity of such screening tests has not been formally evaluated.
Objective
To evaluate the performance of an Alzheimer-selective odor identification test in patients with PD and its relationship with cerebral dopamine transporter (DAT) activity.
Methods
PD patients (n=44; Hoehn and Yahr stages I–III; 13f/31m; mean age 59.3±10.1) and 44 controls matched for gender and age completed the University of Pennsylvania Smell Identification Test (UPSIT). All patients had PD duration>1 year and none had evidence of dementia. Using the UPSIT, we calculated performance on the 10 odors previously reported to be selective for AD risk (UPSIT-AD10). A subset of 29 PD patients also underwent brain DAT [11C]β-CFT (2-β-carbomethoxy-3β-(4-fluorophenyl) tropane) PET imaging. DAT binding was assessed in the hippocampus, amygdala, ventral and dorsal striatum.
Results
UPSIT-AD10 scores were significantly lower in the patient (5.8±2.1) compared to the control group (8.6±2.4) (t=5.8, P<0.0001). However, UPSIT-AD10 performance in the PD patients did not correlate with striatal or mesolimbic DAT activity.
Conclusions
Hyposmia in PD and AD overlap and supposed Alzheimer-selective smell screening tests may not be specific for AD. However, the supposed AD-selective hyposmia scores in PD did not correlate with cerebral DAT binding and may reflect a non-dopaminergic olfactory mechanism.
aDepartment of Neurology, University of Michigan, Ann Arbor, MI, USA
bDepartment of Neurosurgery, University of Michigan, Ann Arbor, MI, USA
cDepartment of Neurology, University of Pittsburgh, Pittsburgh, PA, USA
dDepartment of Radiology, University of Pittsburgh, Pittsburgh, PA, USA
Corresponding author. University of Michigan Medical School, 1500 E. Medical Center Drive, SPC 5316, 1914 Taubman Center, Ann Arbor, MI 48109-5316, USA. Tel.: +1 734 936 9045; fax: +1 734 936 8763.
1 Present address: Functional Neuroimaging, Cognitive and Mobility Laboratory, Departments of Radiology & Neurology, University of Michigan Medical School, Ann Arbor, MI, USA.
ABSTRACT