Olfactory and gustatory functioning and food preferences of patients with Alzheimer’s disease and mild cognitive impairment compared to controls: the NUDAD project

Abstract

Our aim is to compare olfactory and gustatory function and food preferences of patients with Mild Cognitive Impairment (MCI) and Alzheimer's disease (AD) with controls. We included 22 patients with MCI, 30 patients with AD and 40 controls and assessed olfactory threshold, odor discrimination and odor identification (Sniffin' Sticks), gustatory functioning (Taste Strips), and food preferences (Macronutrient and Taste Preference Ranking Task). Linear regression analyses were used to study associations of five cognitive domains or AD biomarkers with olfactory functioning. Groups did not differ in olfactory threshold, gustatory function and food preferences. Patients with MCI and AD scored lower on odor discrimination and identification than controls. Poorer memory, but no other cognitive domain, was associated with poorer odor discrimination and odor identification, but not with odor threshold. No associations with AD biomarkers were found. In conclusion, patients with MCI and AD have poorer odor discrimination and identification ability than controls, but similar detection thresholds. This is likely a consequence of poorer memory rather than directly caused by AD pathology.

Olfactory impairment in men and mice related to aging and amyloid-induced pathology

“…[ 72 ]). Similar results were also obtained by other groups [ 44 , 68 , 91 ], reporting significantly lower odor identification ability of 60–75-year-old AD patients compared to age-matched controls.…”

“…This difference, however, did not reach the level of statistical significance. A recent study on somewhat younger AD patients (69.5 ± 9.4 years old) also failed to find any difference in the odor threshold sensitivity between AD patients and the age-matched (62.5 ± 6.8 years old) control group [ 44 ].…”

“…Recent studies have demonstrated that AD patients are often impaired in the ability to correctly identify a given odorant [ 44 , 68 , 72 , 91 , 123 ]. Typically, this disability is much more profound than the problem with the odor detection threshold [ 125 ].…”

“…Data are taken from refs. [ 41 , 43 , 44 , 68 , 78 , 96 , 97 , 117 , 128 , 143 , 144 ]. Y -axis is shown in arbitrary units …”

Association of Odor Identification Ability With Amyloid-β and Tau Burden: A Systematic Review and Meta-Analysis

“…Concerning other olfactory functions, a recently published study (Lian et al, 2019) investigated the relationship between the threshold discrimination identification score and CSF Aβ and tau levels in AD patients with or without olfactory dysfunction (OD), finding that only t-tau levels were significantly lower in the AD-OD group, but the significant correlation disappeared after adjusting for age, sex, education, and disease duration. The same was true for the study by Doorduijn et al (2020), which found no associations between AD biomarker levels and threshold discrimination identification. Another excluded study using odor percept identification performance with a homemade test to correlate with Aβ PET data also yielded a negative result (Dhilla Albers et al, 2016).…”