Verification of the association between cognitive decline and olfactory dysfunction using a DEmentia screening kit in subjects with Alzheimer's dementia, mild cognitive impairment, and normal cognitive function (DESK study): A multicenter, open-label, interventional study

BACKGROUND AND PURPOSE: Olfactory dysfunction may be an early symptom of degenerative neurological disorders such as mild cognitive impairment (MCI), which may progress to cognitive decline and Alzheimer's disease (AD). We investigated the relationship between cognitive decline and olfactory dysfunction in healthy controls and patients with MCI or AD using the DEmentia Screening Kit (DESK), an olfactory identification assessment tool designed for Japanese populations. METHODS: In this multicenter, open-label, interventional study conducted from 16 September 2020 to 30 April 2021, participants underwent olfactory tests using the DESK tool. This included 10 odorants at two concentrations (weak/strong) including toothpaste, butter, and India ink. RESULTS: Among 223 participants, 100, 61, and 62 were healthy controls, MCI patients, and AD patients (mean ages, 57.4, 72.8, and 76.3 years; total DESK olfaction scores, 18.4, 14.7, and 7.4), respectively. Significant differences in total olfaction scores were observed between groups (healthy controls vs MCI, healthy controls vs AD, and MCI vs AD). Significant between-group total score differences were shown for olfaction scores with both the 10 strong and 10 weak odorant varieties. CONCLUSION: The DESK tool may discriminate between healthy individuals and those with MCI or AD, facilitating early screening for cognitive decline among Japanese patients, although the effect of age on DESK olfaction scores has not been fully explored.