This Doctor of Philosophy (PhD) project is part of a larger project on potentially modifiable risk factors for dementia in a life course perspective, with an overarching aim to improve prevention of dementia and thereby potentially relieve patient and caregiver distress and decrease societal load. The present PhD project will concentrate on confirming knowledge of HI as an independent risk factor for dementia and exploring potentially causative factors to explain this relationship.

Despite a huge increase in the knowledge about disease mechanisms in various types of dementia in recent years, no curative treatment exists at present. Results from research on disease-modifying agents have been disappointing. This has led to an increased interest in other ways to reduce the prevalence of dementia. A recent report estimated that up to one third of dementia cases could be delayed or prevented by interventions directed at the most common risk factors. In the "Lancet commission on dementia prevention, treatment, and care", hearing impairment (HI) was identified as the potentially most important modifiable risk factor. Even though HI is considered an important modifiable risk factor, the evidence regarding the association between HI and dementia risk is still limited.

Inclusion Criteria:

• Living in designated area

Exclusion Criteria:

• None

HUNT2 and HUNT4 hearing studies: Participants from 17 of the 24 municipalities in the county were offered and accepted a hearing examination, consisting of pure-tone audiometry and two questionnaires on hearing issues, such as use of hearing aids, noise exposure, and tinnitus.

HUNT4 70+/HUNT Trondheim 70+: All participants 70 years of age or older are invited to participate in HUNT4 70+ including cognitive screening examinations.