Volume 122, Issue 7 pp. 1455-1462
Allergy/Rhinology

Olfactory identification testing as a predictor of the development of Alzheimer's dementia: A systematic review

Gordon H. Sun MD

Corresponding Author

Gordon H. Sun MD

Robert Wood Johnson Foundation Clinical Scholars , University of Michigan, Ann Arbor, Michigan

VA Center for Clinical Management Research , VA Ann Arbor Healthcare System, Ann Arbor, Michigan

Department of Otolaryngology–Head and Neck Surgery , University of Michigan, Ann Arbor, Michigan

6312 Medical Science Building I, 1150 W. Medical Center Drive, SPC 5604, Ann Arbor, MI 48109-5604Search for more papers by this author
Cyrus A. Raji MD, PhD

Cyrus A. Raji MD, PhD

Department of Radiology, University of California-Los Angeles, Los Angeles, California, U.S.A.

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Mark P. MacEachern MLIS

Mark P. MacEachern MLIS

A. Alfred Taubman Health Sciences Library , University of Michigan, Ann Arbor, Michigan

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James F. Burke MD, MS

James F. Burke MD, MS

Robert Wood Johnson Foundation Clinical Scholars , University of Michigan, Ann Arbor, Michigan

VA Center for Clinical Management Research , VA Ann Arbor Healthcare System, Ann Arbor, Michigan

A. Alfred Taubman Health Sciences Library , University of Michigan, Ann Arbor, Michigan

Department of Neurology , University of Michigan, Ann Arbor, Michigan

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First published: 02 May 2012
Citations: 74

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.

Abstract

Objectives/Hypothesis:

To evaluate the utility of olfactory identification tests as prognostic instruments for Alzheimer's dementia (AD).

Study Design:

Systematic review.

Methods:

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.

Results:

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.

Conclusions:

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.

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