Prevalence of Alzheimer's Disease Pathology in the Community

The goal of this observational study is to (I) study the proportion of people with Alzheimer's disease pathology in a large Norwegian population-based cohort of people aged 70 years or older and to (II) study longitudinal changes of Alzheimer's disease pathology in the same population over a 14 year period. The main aims are: * What is the proportion of people with Alzheimer's disease pathology, defined by elevated plasma p-tau217, in a large Norwegian population-based cohort of people aged 70 years or older. * What is the proportion of people with Alzheimer's disease pathology, defined by elevated plasma p-tau217, among those with normal cognition, mild cognitive impairment and dementia in a large Norwegian population-based cohort of people aged 70 years or older. * What is the association between plasma p-tau217 concentration and mild cognitive impairment or dementia 4, 10 and 14 years later, respectively. * What is the association between plasma NfL concentration and mild cognitive impairment or dementia 4, 10 and 14 years later, respectively. Data is used from The Nord-Trøndelag Health Study (HUNT) wave 3 (2006-2008) and 4 (2017 - 2019, also including HUNT AiT 2021-2023).