To evaluate the utility of olfactory identification tests as prognostic instruments for Alzheimer’s dementia (AD).
In accordance with PRISMA guidelines, PubMed and Ovid MEDLINE, EMBASE, ISI Web of Science, PsycINFO, the Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials were searched to determine the quality and quantity of longitudinal and cross-sectional research on this topic.
Two prospective longitudinal cohort studies and 30 cross-sectional studies met inclusion criteria. The prospective longitudinal studies evaluated subjects with or without mild cognitive impairment (MCI) while also using olfactory identification testing as part of a neurocognitive evaluation. The first study reported an increased risk of later onset of AD in subjects with baseline hyposmia, whereas the second study suggested a possible relationship between decreased olfaction in participants with MCI and conversion to AD but was inconclusive due to low follow-up rates. Wide variability in the type of olfactory identification test used and the reporting of results precluded meta-analysis. The cross-sectional studies demonstrated a positive association between poorer performance on olfactory identification testing and AD.
Although there is evidence suggesting an association between decreased olfaction and AD, rigorously designed longitudinal cohort studies are necessary to clarify the value of olfactory identification testing in predicting the onset of AD.
Cyrus A. Raji MD, PhD6,
Mark P. MacEachern MLIS4,
James F. Burke MD, MS1,2,4,5
Article first published online: 2 MAY 2012
Copyright © 2012 The American Laryngological, Rhinological, and Otological Society, Inc.
Gordon Sun, MD and James Burke, MD are Robert Wood Johnson Foundation Clinical Scholars supported by the US Department of Veterans Affairs. The Robert Wood Johnson Foundation and the Department of Veterans Affairs were not directly involved in study design, data acquisition and interpretation, or manuscript preparation or review. Any opinions expressed herein do not necessarily reflect the opinions of the Robert Wood Johnson Foundation or the Department of Veterans Affairs.
The authors have no other funding, financial relationships, or conflicts of interest to disclose.