To investigate the association between hearing loss, hearing aid use, and cognitive decline. Prospective population-based study. Data gathered from the Personnes Agées QUID study, a cohort study begun in 1989-90. Individuals aged 65 and older (N = 3,670). At baseline, hearing loss was determined using a questionnaire assessing self-perceived hearing loss; 137 subjects reported major hearing loss, 1,139 reported moderate problems (difficulty following the conversation when several persons talk at the same time or in a noisy background), and 2,394 reported no hearing trouble. Cognitive decline was measured using the Mini-Mental State Examination (MMSE), administered at follow-up visits over 25 years. Self-reported hearing loss was significantly associated with lower baseline MMSE score (β = -0.69, P < .001) and greater decline during the 25-year follow-up period (β = -0.04, P = .01) independent of age, sex, and education. A difference in the rate of change in MMSE score over the 25-year follow-up was observed between participants with hearing loss not using hearing aids and controls (β = -0.06, P < .001). In contrast, subjects with hearing loss using a hearing aid had no difference in cognitive decline (β = 0.07, P = .08) from controls. Self-reported hearing loss is associated with accelerated cognitive decline in older adults; hearing aid use attenuates such decline.