A brief olfactory test for Alzheimer's disease.
BACKGROUND
The early diagnosis of Alzheimer's disease (AD) may help reduce disability, enhance quality of life, and aid clinical trials. Portions of olfactory cortex are the initial sites of AD pathology and patients with AD often have more degeneration of their left than right hemisphere. Since the olfactory epithelium projects mainly to the ipsilateral olfactory cortex, patients with AD may demonstrate an asymmetrical (left greater than right) decrement of odor detection sensitivity. This retrospective, case-control study assessed a quick olfactory test that may help diagnose AD.


METHODS
Participants with probable AD (N=18), mild cognitive impairment (MCI, N=24), other causes of dementia (OD, N=26) and matched controls (OC, N=26) were tested, with closed eyes, for their ability to detect an odor, one nostril at a time. A container of 14g of peanut butter was opened, held medially at the bottom of a 30cm ruler, and moved up 1cm at a time during the participants' exhale. Upon odor detection, the distance between the subject's nostril and container was measured.


RESULTS
The mean odor detection distance of AD patients' left nostril (5.1cm), and not their right (17.4cm), was significantly less (F(3,90)=22.28, p<0.0001) than the other groups. The mean, standard error, and 95% Confidence Interval of the L-R nostril odor detection difference (cm) for AD were -12.4±0.5, (-15.0,-9.8); for MCI were -1.9±1.2, (-4.2,0.4); for OD were 4.8±1.0, (2.6,6.9); and for OC were 0.0±1.4 (-2.2,2.1).


CONCLUSIONS
This non-invasive and inexpensive left-right nostril odor detection test appears to be a sensitive and specific test for probable AD.
Department of Neuroscience, The Clinical and Translational Science Institute, University of Florida, College of Medicine, Gainesville, FL, USA. Electronic address: jstamps@ufl.edu.
Jennifer J
JJ
Stamps
Linda M
LM
Bartoshuk
Kenneth M
KM
Heilman
D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis* / Q000503:physiopathology*; D016022:Case-Control Studies; D060825:Cognitive Dysfunction / Q000175:diagnosis / Q000503:physiopathology; D003943:Diagnostic Techniques, Neurological; D042241:Early Diagnosis; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D055696:Olfactory Perception / Q000502:physiology*; D012189:Retrospective Studies
Alzheimer disease; Cranial nerve I disorders; Neurologic examination; Odor detection; Olfaction; Smell disorders