Seven-year longitudinal data reveals hearing aid intervention lowered dementia incidence by approximately 40% in adults with moderate hearing loss, even though cognitive test batteries showed no measurable improvement in memory or executive function during the study period. This paradoxical finding suggests hearing aids may protect against neurodegeneration through mechanisms beyond simple cognitive enhancement—potentially by reducing social isolation, decreasing cognitive load, or maintaining neural pathway integrity through preserved auditory input. The research adds compelling evidence to the emerging consensus that sensory preservation represents a modifiable dementia risk factor, joining hypertension management and physical activity as actionable interventions. However, the disconnect between cognitive testing and real-world dementia outcomes highlights limitations in current neuropsychological assessments, which may miss subtle but clinically meaningful changes in daily functioning. The protective effect likely operates through complex pathways involving social engagement, reduced listening effort, and maintained brain stimulation rather than direct cognitive enhancement. For the estimated 466 million adults with disabling hearing loss worldwide, this represents a readily available intervention that could substantially impact population-level dementia rates, though longer-term studies are needed to confirm durability of protection.