AGE-RELATED HEARING LOSS AND COGNITIVE DECLINE IN THE GENERAL POPULATION

Abstract

Hearing loss has recently been identified as a potentially modifiable risk factor for dementia.1-5 However, results from cross-sectional studies have been conflicting, possibly due to interrelated effects of age on both hearing and cognitive function or reverse causality. Therefore longitudinal population-based studies are needed to elucidate whether hearing loss is independently associated with cognitive decline, while adjusting for the effects of age over time. 4,306 non-demented participants (mean age 64.4 [SD: 6.9], 59.3% female) underwent baseline hearing assessment with pure-tone audiometry (2011-2014).6 Cognitive function was assessed at baseline and on average 4.4 years at follow-up (SD: 0.2), with an extensive test battery consisting of the MMSE, Stroop test, Word Fluency test (WFT), Letter Digit Substitution test (LDST), Word Learning test (WLT) and the Purdue Pegboard test (PPT). Linear mixed models were used to elucidate the longitudinal association between hearing loss and cognitive function for each test separately. Hearing loss was entered into the models on a continuous scale (per 10 decibel [dB] increase), and subsequently per degree of hearing loss (mild, moderate, severe), compared to none hearing loss. Follow-up time was used as the time variable and the models were adjusted for age, sex, education, and cardiovascular risk factors. In an extended model, we additionally adjusted for the interaction between age and follow-up time. Hearing loss per 10 dB increase did not alter cognitive function over time. When comparing the trajectories of degree of hearing loss of the cognitive test scores over time, we demonstrated that degree of hearing loss showed significant lower scores compared to none hearing loss for the MMSE, WFT, LDST, WLT, and PPT (figure 1). However, no significant slope differences remained after adjustment for the interaction between age and follow-up time (figure 2).