Smell identification function in early-onset Alzheimer's disease and mild cognitive impairment.

Emily Penney,Frances Wilson-Morkeh,Amala Jovia Maria Jesu,Sarah Baillon,Latha Velayudhan,Traolach Brugha

doi:10.1017/s1041610218001503

Abstract

Little is known about olfactory identification (OI) function in early-onset Alzheimer's disease (EOAD) and early-onset mild cognitive impairment (eoMCI) with age of onset <65 years. We aimed to study OI in EOAD compared with eoMCI and age-matched healthy controls (HC). Nineteen EOAD subjects with mild to moderate dementia, 17 with eoMCI, and 21 HC recruited as a convenience sample from memory services were assessed for cognition, behavioral symptoms, and activities for daily living. The OI was tested using the University of Pennsylvania smell identification test (UPSIT). EOAD participants performed worse compared with eoMCI and HC on cognitive tests and OI (p < 0.001). Although eoMCI had poorer cognitive scores compared to HC, they were similar in their OI function. OI correlated with attention (r = 0.494, p = 0.031), executive functions (r = 0.508, p = 0.026), and praxis (r = 0.455, p = 0.05) within the EOAD group. OI impairment was significantly associated with the diagnosis of EOAD versus eoMCI, but not with eoMCI when compared with HC. OI could potentially be useful in differentiating EOAD from eoMCI. Studies with late-life MCI patients showing OI impairment relative to HC may be attributed to a different disease process. Independent replication in a larger sample is needed to validate these findings.

Highlights

Olfactory dysfunction in general and impaired olfactory identification (OI) in particular have been reported in Alzheimer’s disease (AD) and are found to occur at early stages of the disease (Mesholam et al, 1998)
The early onset mild cognitive impairment (MCI) (eoMCI) participants scored lower than healthy controls (HC) group on the MMSE (t(36)=-4.241, p
Albeit in a small sample, the findings of our study are interesting in that it shows impaired OI in people with early onset AD (EOAD) compared to eoMCI and HC

Summary

Introduction

Olfactory dysfunction in general and impaired olfactory identification (OI) in particular have been reported in Alzheimer’s disease (AD) and are found to occur at early stages of the disease (Mesholam et al, 1998). All published reports of OI in AD have demonstrated deficits related to healthy controls (Rahayel et al, 2012) and its utility as a biomarker to predict cognitive decline and AD in elderly cognitively normal people and those with mild cognitive impairment (MCI) (Devanand et al, 2015; Lafaille-Magnan et al, 2017; Woodward et al, 2017). It is well established that patients with late onset AD and elderly MCI perform significantly more poorly than matched controls in their olfactory identification function, there is little information on OI in people with early onset AD (EOAD) and early onset MCI (eoMCI) (

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