BACKGROUND: Hearing loss poses a significant global public health concern associated with cognitive decline. Among the many risk factors associated with Alzheimer's disease and related dementia (ADRD), hearing loss is the most prevalent sensory impairment in older adults and has emerged as a significant, yet often overlooked, modifiable risk factor for dementia. OBJECTIVES: To access 1) the association between diet and risk of hearing loss in older adults and 2) the modifying effect of diet on the impact of hearing loss on cognitive decline in an aging population. DESIGN: Prospective cohort study SETTING: The Chicago Health and Aging Project, a community-based cohort study PARTICIPANTS: A total of 5,145 older adults (62 % non-Hispanic Black, 63 % female). MEASUREMENTS: Self-reported hearing ability was assessed during each cycle of data collection. Diet was assessed by a 144-item Food Frequency Questionnaire. Diet quality was evaluated using a 144-item Food Frequency Questionnaire, focusing on adherence to dietary patterns such as Dietary Approaches to Stop Hypertension (DASH), Mediterranean, and Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND). Cognitive function assessment was conducted during the in-home visits at each cycle. Four cognitive tests, including the East Boston tests of immediate and delayed recall, the mini-mental State Examination, and the Symbol Digit Modalities test, were included. We used linear mixed effect models to examine 1) the association of hearing loss and cognitive decline and 2) the association of diet on cognitive decline through modifying risk hearing loss. Discrete-time survival analysis examined the association between dietary patterns and the time to hearing impairment. RESULTS: Among 5,145 participants included in the analyses, 747 (14.5 %) reported hearing loss, including 207 Black adults and 199 White adults. Each unit increase in the DASH, MedDiet, and MIND scores was associated with 19 % (95 % CI: 0.79, 0.94, P < 0.001), 11 % (95 % CI: 0.79, 1.00, P = 0.05), and 13 % (95 % CI: 0.87, 0.99, P < 0.05) lower risk for hearing loss, respectively. High adherence to the Western diet was associated with an earlier onset of hearing loss up to 14 months (P < 0.05). Participants had an increased rate of cognitive decline after reporting hearing loss. During follow-up, participants in the highest tertile of the DASH diet score who reported hearing loss experienced a 17 % faster cognitive decline (β = -0.07 ± 0.01) compared to those without hearing loss (β = -0.06 ± 0.003). However, this decline was significantly slower than that of participants observed in the lowest tertile of the DASH diet, who exhibited a 67 % faster cognitive decline (β = -0.10 ± 0.012, P = 0.05). DISCUSSION: Healthy dietary patterns, particularly the DASH diet, was associated with a reduced risk of hearing loss and slower cognitive decline following hearing loss. Clinically, these findings underscore the importance of dietary quality in preserving cognitive health by potentially mitigating risk of hearing loss or delaying the onset of hearing loss in older adults.