Odour-Specific Identification Impairment Is Associated With Cognitive Dysfunction in Older Adults: A Contemporary Community-Based Study.

Background: To delay or prevent the development of MCI, identifying a potential target is essential. Olfactory dysfunction has been linked to MCI. However, it remains unclear to what extent odour-specific identification impairment affects domain-specific cognition. Therefore, we aimed to investigate the association of olfactory dysfunction and odour-specific identification impairment with cognitive domains in older adults.

Methods: In 1084 community-dwelling older adults from the Chinese Multi-Provincial Cohort Study, olfactory function was assessed using the modified Sniffin' Sticks identification test, and impaired odour identification was defined as an incorrect identification of one odour. Olfactory dysfunction was defined as three or more odours. Cognition was assessed using MOCA, comprised of six cognitive domains. MCI was defined as an education-modified MOCA score of < 26.

Results: Overall, 35.6% of participants had olfactory dysfunction, and 60.1% had MCI. Participants with olfactory dysfunction had a higher risk of MCI and exhibited lower global cognitive function than those without olfactory dysfunction. Notably, impaired odour identification of fish (OR = 1.48, 95% CI: 1.03-2.13) and leather (OR = 1.45, 95% CI: 1.09-1.92) was significantly associated with the risk of MCI. Furthermore, impaired odour identification of all odours except rose was significantly associated with global cognitive function. Participants with impaired odour identification of fish and leather had significantly poorer memory than unimpaired participants.

Conclusions: Our findings demonstrated that impaired identification of specific odours increased the risk of MCI and domain-specific cognitive dysfunction, suggesting that odour identification impairment may thus be a potential target for future MCI/dementia intervention studies.