Hearing loss and incidence of dementia: A large cohort study covering the Region of Southern Denmark.

There is a growing body of evidence linking hearing loss with an increased risk of cognitive impairment and dementia. However, there is still much to be explored in relation to the nature of this relationship and whether hearing loss is a risk factor for dementia. We aim to investigate the association between hearing loss and risk of dementia in a large cohort including all older adults (≥ 50 years old) living in the Region of Southern Denmark between 1998 and 2017. Detailed hearing loss information is extracted from the HESD database, a recently established database containing data of all hearing examinations (e.g., pure-tone audiometry) carried out at the public health system of the Region of Southern Denmark for approximately 20 years and approximately 145,000 patients. Incident dementia cases are identified from national hospital and prescription registries. Due to clinic-specific variability in terms of hearing data collection, we will start follow-up in 2003 or 2008 (depending on location), to ensure residence in the region for at least five years. Hazard ratios will be calculated with Cox Proportional Hazard models, with adjustment for socio-demographic covariates. We will evaluate possible effect modification of the association by including interaction terms between hearing loss and different covariates, such as sex, age, occupation, and hearing loss asymmetry and configuration. Given the longitudinal approach and larger sample size in comparison to most existent studies on the topic, we expect to contribute to the current knowledge and provide new insights on the relationship between hearing loss and dementia.