Hearing loss as a risk factor for dementia: a systematic review and meta-analysis from a global perspective.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of prospective observational cohort studies
PubMed 40511666 · doi:10.1080/13607863.2025.2515180
What was done
The authors conducted a systematic review and meta-analysis of prospective cohort studies searched across MEDLINE, PsychInfo, Academic Search Ultimate, Web of Science, and EMBASE from inception to 2024. Eligible studies enrolled dementia-free individuals with baseline hearing assessments, at least 2 years of follow-up, and incident dementia outcomes. Random-effects and multilevel models with subgroup difference tests were used to assess the association and intercontinental variability.
What was found
Forty-nine cohort studies were included: 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). Hazard ratios were largest for Oceania and smallest for Asia (p < 0.001), but did not differ significantly by continent when excluding Oceania. Analyses stratified by severity yielded imprecise estimates: mild (HR = 1.35, 95% CI: 0.86–2.11), moderate (HR = 1.39, 95% CI: 0.57–3.35), and severe (HR = 1.66, 95% CI: 0.59–4.64), with limited evidence of continental differences by severity (p = 0.059).
Why it matters
This review synthesizes global longitudinal evidence confirming hearing loss as a consistent risk factor for dementia across continents, though variation exists by region.
Limits
The total number of individual participants is not reported in the abstract. All included studies are observational cohorts, which cannot establish causality. Data were heavily skewed toward North America and Europe, with very few studies from Asia and Oceania and none from Africa or South America. Severity-specific estimates were underpowered and imprecise.