[P4–344]: HEARING LOSS AND RISK OF INCIDENT COGNITIVE IMPAIRMENT AND DEMENTIA: A META‐ANALYSIS OF COHORT STUDIES

Hearing loss has been linked to increased risk of cognitive decline and dementia. To quantify this risk we are conducting a meta-analysis of cohort studies monitoring hearing and cognition longitudinally. This meta-analysis has been prospectively registered (CRD42016048835). We identified cohort studies that included hearing assessments in participants without a dementia diagnosis at baseline; follow-up had to include an assessment of cognition. We used random-effects meta-analysis in R statistical software to compute pooled estimates of adjusted relative risks (RR). Initial analysis of 11 studies (174885 participants) with a follow up of 4 to 17 years, shows that hearing loss increases the risk of incident cognitive impairment and dementia, with RR = 1.35 (95% CI 1.21–1.51; p<0.001; heterogeneity: I= 15%, p = 0.302). Whether studies adjusted for education, baseline cognition, cardiovascular risk, the duration of follow-up, or the method of hearing assessment, does not change the RR pooled estimates significantly (meta-regression, all p-values >0.1). When we include only the highest quality studies, meeting 3 pre-specified criteria (use of pure tone audiometric thresholds, follow up of at least 5 years, and dementia diagnosis with recognised criteria), hearing loss remains a statistically significant risk factor for incident dementia (RR = 1.66; 95% CI 1.11–2.49; p = 0.014; heterogeneity: I= 38%, p = 0.202; 3 studies, 3585 participants). Hearing loss increases the risk of incident cognitive decline and dementia in cohort studies. This association is robust to differences in study design, and to adjustment by age, cardiovascular risk and other potential confounders. Future studies should investigate the mechanisms of this increased risk, and whether it can be reduced by treating hearing loss.