Associations of olfaction with mild cognitive impairment and cognitive function in older adults: A population‐based study

Abstract

AbstractBackgroundOlfactory function might be impaired in the early stage of the dementing process, and thus, olfactory test may be useful for identifying elderly persons at an increased risk. However, previous studies that investigate the relationship between olfactory function and cognitive phenotypes have been scarcely conducted among older people living in the rural communities and the associations of olfaction with specific cognitive remains unclear. We sought to examine the relationship of olfactory function with global cognitive ability and various domains of cognitive function among rural‐dwelling Chinese older adults.MethodThis population‐based cross‐sectional study included 3003 dementia‐free participants (age ≥65 years; 57.3% women; 37.7% illiterate) in the baseline examination (March‐September 2018) of the Multidomain Interventions to Delay Dementia and Disability in Rural China (MIND‐CHINA) study. The 16‐item Sniffin’ Sticks identification test (SSIT) was performed to assess olfactory function. Global cognitive function was evaluated with the Chinese version of the Mini‐Mental State Examination (MMSE) and a neuropsychological battery was used to assess memory, language, attention, and executive function. We followed the Petersen’s criteria to define mild cognitive impairment (MCI). Data were analysed with multiple logistic regression and the general linear regression models.ResultOf the 3003 participants, MCI was defined in 335 persons (11.2%). Multiple logistic regression analysis suggested that SSIT score (range 0‐16) was associated with an odds ratio of 0.90 (95% CI 0.87‐0.93) for MCI. Multiple general linear regression analysis showed that SSIT score was significantly associated with the scores of MMSE test (β coefficient=0.07, 95% CI 0.03‐0.11), z‐score of memory (β coefficient=0.28, 95% CI 0.12‐0.45), language (β coefficient=0.35, 95% CI 0.17‐0.52), and attention (β coefficient=0.59, 95% CI 0.38‐0.78), but not with the z‐score of executive function (β coefficient=0.05, 95% CI ‐0.11‐0.22).ConclusionA greater olfactory identification ability is associated with a lower likelihood of MCI and better performances in global cognitive function, attention, memory, and language function, but not in executive function, among Chinese older adults who are living in the rural communities with limited education.