Objectives
Hearing loss is a risk factor for dementia with estimated hazard ratios (HRs) of 1.28–2.39. However, whether intercontinental variability exists in this relationship remains unexplored.

Method
MEDLINE, PsychInfo, Academic Search Ultimate, Web of Science, and EMBASE were searched, from inception to 2024, for cohort studies of dementia-free individuals with baseline hearing assessments ≥2-year follow-up, and incident dementia outcomes. Random-effect and multilevel models with subgroup difference tests were conducted.

Results
Forty-nine studies analysed cohorts from North America (n = 20), Europe (n = 20), Asia (n = 7), and Oceania (n = 2). Binary hearing loss was associated with increased dementia risk (HR = 1.32 [95% CI: 1.23–1.41]) with HRs being largest for Oceania and smallest for Asia (p <0.001). In a sensitivity analysis excluding Oceania, HRs did not differ significantly by continent. Imprecise estimates create uncertainty around whether mild (HR = 1.35 [95% CI: 0.86–2.11]), moderate (HR = 1.39 [95% CI: 0.57–3.35]) or severe (HR = 1.66 [95% CI: 0.59–4.64]) hearing loss are associated with increased dementia risk, with little evidence that HRs by severity differ by continent (p = 0.059).

Conclusion
Findings indicate that the association between hearing loss and dementia is consistent globally, though HRs may vary slightly by continent.

Registration
This review was pre-registered on PROSPERO (CRD42024545209) and the OSF (https://osf.io/kew29/).