Additive Effects of Olfactory and Auditory Dysfunction on Cognitive Impairment in Older Adults

Disturbance of hearing or olfaction is known to be associated with cognitive impairment. Multisensory impairment-simultaneous dysfunction in multiple senses-is common among older adults. This study examined the relationship between cognitive impairment and the co-occurrence of olfactory and auditory dysfunctions in older adults.

Data were obtained from a population-based survey. Of 1346 randomly selected residents, 527 participated; after excluding 22 with incomplete data, 505 residents aged 65-84 years were enrolled. Cognitive function was assessed using the Japanese Quick Mild Cognitive Impairment Screen (Qmci-J). Olfactory and auditory function, assessed using the Open Essence test and pure-tone audiometry, respectively, were classified as normal, moderate, or severe, yielding nine combined groups. Associations with cognitive impairment (Qmci-J ≤ 60) were examined using modified Poisson regression to estimate the prevalence ratio (PR), adjusting for demographic, health-related, and socioeconomic covariates.

Among 505 participants, 225 (44.6%) had cognitive impairment. Severe dysfunction in either olfaction or audition, combined with at least moderate dysfunction in the other, was significantly associated with cognitive impairment. The highest PR was observed in participants with severe dysfunction in both senses (PR = 1.90, 95% CI: 1.16-3.10). These associations remained significant even after adjustment for all covariates. Although no significant additive or multiplicative interaction was observed, the co-occurrence of severe olfactory and auditory dysfunctions showed the highest PR, consistent with an additive effect.

Olfactory and auditory dysfunctions are additively associated with cognitive impairment, highlighting the importance of considering multisensory impairment in older adults.

The technical efficacy of this study is high. The study design, data collection procedures, and statistical analyses are clearly described and reproducible. In addition, all key assessments used in this study, including the Quick Mild Cognitive Impairment Screen (Qmci), the Open Essence Test, and pure-tone audiometry, are standardized, validated, and widely accepted measures, as detailed in the manuscript.