Increase Risk of Dementia in Patients With Sudden Hearing Loss: A Population-Based Cohort Study With 7-Year Follow-Up in Taiwan.

OBJECTIVE: To investigate the prevalence and risk of subsequent dementia in subjects with sudden hearing loss during a 7-year follow-up period through comparisons with cohorts matched by sex, age group, and year of index date. STUDY DESIGN: A retrospective matched-cohort study. SETTING: The Longitudinal Health Insurance Database 2000 (LHID2000) in Taiwan. PATIENTS: This study included a total of 11,148 subjects, including 1,858 in the study group and 9,290 in the comparison cohort group. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): We analyzed the differences in sociodemographic characteristics and comorbidities between subjects with sudden hearing loss and the comparison cohort group. Then, we estimated the risk of dementia and also plotted the survival outcomes to evaluate differences in dementia-free survival rates between the two groups. RESULTS: The dementia incidence rates per 1000 person-years were 20.45 and 8.15 for the subjects with sudden hearing loss and comparison cohorts, respectively. When we adjusted for the subjects' characteristics, the hazard ratio for dementia was 1.69 (95% confidence interval [CI] = 1.06-2.68, p < 0.01) for subjects with sudden hearing loss compared with comparison cohorts during the follow-up period, and subjects with sudden hearing loss had lower 7-year dementia-free survival rates compared with comparison cohorts by using a log-rank test. Furthermore, male subjects with sudden hearing loss had a higher risk of dementia (adjusted hazard ratio [HR] = 2.11) than did the male comparison cohorts. CONCLUSIONS: This study revealed a relationship between sudden hearing loss and dementia in an Asian country. The risk of dementia was higher among patients with sudden hearing loss compared with matched cohorts during the 7-year follow-up period.