Olfactory Impairment Among Rural-Dwelling Chinese Older Adults: Prevalence and Associations With Demographic, Lifestyle, and Clinical Factors

Yi Dong; Yongxiang Wang; Keke Liu; Rui Liu; Shi Tang; Qinghua Zhang; Ingrid Ekström; Erika J Laukka; Yifeng Du; Chengxuan Qiu

doi:10.3389/fnagi.2021.621619

Olfactory Impairment Among Rural-Dwelling Chinese Older Adults: Prevalence and Associations With Demographic, Lifestyle, and Clinical Factors

Front Aging Neurosci. 2021 Apr 12:13:621619. doi: 10.3389/fnagi.2021.621619. eCollection 2021.

Authors

Yi Dong¹, Yongxiang Wang^{1

2}, Keke Liu^{1

2}, Rui Liu¹, Shi Tang^{1

2}, Qinghua Zhang^{1

2}, Ingrid Ekström³, Erika J Laukka³, Yifeng Du^{1

2}, Chengxuan Qiu^{1

3}

Affiliations

¹ Department of Neurology, Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China.
² Department of Neurology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China.
³ Aging Research Center and Center for Alzheimer Research, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet-Stockholm University, Stockholm, Sweden.

Abstract

Objective: Olfactory impairment (OI) refers to decreased (hyposmia) or absent (anosmia) ability to smell. We sought to estimate the prevalence and correlates of OI among rural-dwelling Chinese older adults. Methods: This population-based cross-sectional analysis included 4,514 participants (age ≥65 years; 56.7% women) from the Multidomain Interventions to Delay Dementia and Disability in Rural China (MIND-China). The 16-item Sniffin' Sticks identification test (SSIT) was used to assess olfactory function. Olfactory impairment was defined as the SSIT score ≤10, hyposmia as SSIT score of 8-10, and anosmia as SSIT score <8. Multivariable logistic regression models were used to examine factors associated with OI. Results: The overall prevalence was 67.7% for OI, 35.3% for hyposmia, and 32.5% for anosmia. The prevalence increased with age for OI and anosmia, but not for hyposmia. The multivariable-adjusted odds ratio (OR) of OI was 2.10 (95% CI 1.69-2.61) for illiteracy and 1.41 (1.18-1.70) for elementary school (vs. middle school or above), 1.30 (1.01-1.67) for current smoking (vs. never smoking), 0.86 (0.74-0.99) for overweight and 0.73 (0.61-0.87) for obesity (vs. normal weight), 4.21 (2.23-7.94) for dementia, 1.68 (1.23-2.30) for head injury, and 1.44 (1.14-1.83) for sinonasal disease. Illiteracy in combination with either male sex or diabetes was significantly associated with an over two-fold increased OR of OI (p for interactions <0.05). Conclusion: Olfactory impairment is highly prevalent that affects over two-thirds of rural-dwelling older adults in China. OI is correlated with illiteracy, current smoking, dementia, head injury, and sinonasal disease, but negatively associated with overweight or obesity. Olfactory impairment as a potential clinical marker of neurodegenerative disorders among older adults deserves further investigation.

Keywords: Sniffin' sticks identification test; anosmia; hyposmia; old age; olfactory impairment; population-based study.