Olfactory identification ability in patients with mild cognitive impairment and Alzheimer’s disease

[Purpose] To examine the olfactory identification abilities and specify the difficult-to-identify odors in community-dwelling individuals with mild cognitive impairment (MCI) and Alzheimer’s disease (AD). [Participants and Methods] We included, 12 and 17 patients with MCI (MCI group) and AD (AD group), respectively, and 30 community-dwelling older adults with no history of MCI or a dementia diagnosis (control group). Scores on the Japanese odor stick identification test (OSIT-J), an olfactory identification ability test, were compared among the three groups with intergroup differences examined accordingly. Next, we performed intergroup comparisons of the ratios of correct responses for each odor, and the difficult-to-identify odors were examined. [Results] OSIT-J scores of the MCI and AD groups were significantly lower than those of the control group. There were no intergroup differences in the correct identification of pungent odors. No patients in the AD group could identify the odor of cooking gas. The ability to identify food-related odors was reduced in the MCI and AD groups. [Conclusion] Patients with MCI and AD had reduced olfactory identification abilities in comparison to community-dwelling older adults without cognitive decline. These findings suggest the importance of olfactory evaluation before providing patients with dementia with therapeutic interventions associated with olfactory stimuli.