The Relationship of Age-Related Hearing Loss with Cognitive Decline and Dementia in a Sinitic Language-Speaking Adult Population: A Systematic Review and Meta-Analysis.

Background and Objectives: Substantial evidence supports the association between untreated hearing loss, cognitive decline, and dementia in the non-tonal language-speaking population. Whether a similar association between hearing loss and cognitive decline and dementia exists in Sinitic tonal language-speaking people is yet to be elucidated. We aimed to systematically review the current evidence on the association between hearing loss and cognitive impairment/decline, and dementia in older adults who speak a Sinitic tonal language. Research Design and Methods: This systematic review considered peer-reviewed articles that employed objective or subjective hearing measurement and cognitive function, cognitive impairment, or diagnosis of dementia. All articles written in English and Chinese and published before March 2022 were included. Databases including Embase, MEDLINE, Web of Science, PsycINFO and Google Scholar, SinoMed, and CBM were utilized using MeSH terms and keywords. Results: Thirty-five articles met our inclusion criteria. Of these, 29 unique studies with an estimated 372,154 participants were included in the meta-analyses. Among all included studies, the effect size of cognitive function with hearing loss, the regression coefficient was -0.26 (95% confidence interval [CI], -0.45 to -0.07). Among cross-sectional and cohort studies, a significant association was found between hearing loss and cognitive impairment and dementia, with odds ratios of 1.85 (95% CI, 1.59-2.17) and 1.89 (95% CI, 1.50-2.38), respectively. Discussion and Implications: Most of the studies included in this systematic review observed a significant association between hearing loss and cognitive impairment and dementia. There was no significant difference to the findings in non-tonal language populations.