Hearing aid effectiveness and probable dementia risk across 33 countries: A pooled analysis of seven cohorts.

Given the inconsistent evidence regarding hearing aid use and reduced dementia risk, this study evaluates whether hearing aid use, particularly effective use, is associated with lower probable dementia risk among hearing-impaired older adults. Using harmonized longitudinal data from 61,089 hearing-impaired participants (aged 55+ years) from seven cohorts (CHARLS, KLOSA, SHARE, ELSA, TILDA, HRS, and MHAS), we employ IPTW-corrected Cox models stratified by country income. Over a 6.5-year average follow-up (8,911 events), hearing aid use is associated with reduced dementia risk (hazard ratio [HR] = 0.91, 95% confidence interval [CI] 0.88-0.94). This association is confined to participants reporting effective hearing improvement (HR = 0.86, 95% CI 0.80-0.93), whereas those reporting poor hearing improvement show no reduced risk (HR = 0.98, 95% CI 0.90-1.07). The association is stronger in middle-income countries (HR = 0.76) and among subgroup populations, including those aged <70 years, women, those who are unmarried, and those with lower education. Quality hearing rehabilitation is a potential public health priority for addressing the dementia burden.