Due to copyright issues, an electronic copy of the thesis must be ordered from the faculty. For the faculty to have time to process the order, the order must be received by the faculty at the latest 2 days before the public defence. Orders received later than 2 days before the defence will not be processed. After the public defence, please address any inquiries regarding the thesis to the candidate.
Trial Lecture – time and place
See Trial Lecture.
Adjudication committee
- First opponent: Associate Professor Sebastian Palmqvist, Lund University
- Second opponent: Associate Professor Ragnhild Eide Skogseth, University of Bergen
- Third member and chair of the evaluation committee: Professor Anners Lerdal, University of Oslo
Chair of the Defence
Professor Emeritus Anne Marit Mengshoel, University of Oslo
Principal Supervisor
Professor II Geir Selbæk, University of Oslo
Summary
Dementia is a major global health challenge, with over 55 million affected worldwide. Hearing impairment and smoking are among modifiable risk factors whose treatment would lead to a reduced and delayed incidence of dementia. The aims of this thesis were to examine, with a long enough follow-up to minimise reverse causation and with adjustment for most relevant covariates, (1) the long-term association between hearing impairment and dementia (2) the impact of hearing impairment on cognitive performance, and (3) the relationship between smoking and dementia risk, including subtype-specific effects and the influence of smoking cessation.
The work is based on the Trøndelag Health Study (HUNT), a large population-based cohort. Hearing status was measured using pure-tone audiometry, smoking status was self-reported, and dementia diagnoses were based on DSM-5 criteria, incorporating neurocognitive tests, daily functioning assessments, and caregiver interviews. The follow-up period spanned more than two decades. Statistical analyses adjusted for confounders estimated risks for dementia and associations with cognitive scores.
Hearing impairment was associated with increased risk of dementia, particularly in individuals younger than 85 years, and with lower scores on the Montreal Cognitive Assessment, especially in memory, orientation, visuospatial and executive domains. Smoking was strongly associated with dementia, with the highest risks observed for vascular dementia. Former smokers did not show increased risk, indicating clear benefits of cessation.
In conclusion, this thesis provides new evidence linking hearing impairment and smoking to dementia and cognitive decline. The results suggest that addressing hearing loss may be most effective in midlife or early old age, and that quitting smoking substantially reduces dementia risk. Public health strategies focusing on hearing care and smoking cessation could help lower the burden of dementia in ageing populations.
Additional information
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