Association of sudden sensorineural hearing loss with dementia: a nationwide cohort study

Background Impaired cochlear blood perfusion and microvascular damage can cause sudden sensorineural hearing loss (SSHL), which is a potential risk factor for dementia. This study explored the association between SSHL and dementia. Methods This retrospective cohort study used a random sample of 1000,000 individuals from Taiwan's National Health Insurance Research Database. We identified 3725 patients newly diagnosed with SSHL between January 1, 2000, and December 31, 2009, and propensity score matching according to age, sex, index year, comorbidities, and medications was used to select the comparison group of 11,175 patients without SSHL. Participants were stratified by age (<65 and >= 65 years) and sex for the subgroup analyses. The outcome of interest was all cause dementia (ICD-9-CM codes 290.0, 290.4, 294.1, 331.0). Both groups were followed up until December 31, 2010, for diagnoses of dementia. Cox regression models were used to estimate the hazard ratio (HR) of dementia. Results During the average 5-year follow-up period, the incidence rate of dementia in the SSHL cohort was 6.5 per 1000 person-years compared with 5.09 per 10,000 person-years in the comparison group. After adjustment for potential confounders, patients with SSHL were 1.39 times more likely to develop dementia than those without SSHL (95% confidence interval = 1.13-1.71). When stratified by patients' age and sex, the incidence of dementia was 1.34- and 1.64-fold higher in patients with SSHL aged >= 65 years (P = .013) and in women (P = .001), respectively, compared with the comparison group. Women with SSHL who were < 65 years old had the highest risk (2.14, 95% CI = 1.17-4.11, P = .022). In addition, a log-rank test revealed that patients with SSHL had significantly higher cumulative incidence of dementia than those without SSHL (P = .002). Conclusions Patients with SSHL, especially women aged < 65 years, were associated with higher risk of dementia than those without SSHL. Thus, clinicians managing patients with SSHL should be aware of the increased risk of dementia.