Alzheimer's disease and vascular dementia in population-based studies

Abstract: Dementia, a clinical syndrome with several profiles and causes, is characterised by a decline in cognitive functions, including memory, learning, executive function, attention, language, and social ability. The most common forms of dementia are Alzheimer’s disease and vascular dementia. As life expectancy is increasing worldwide and age is one of the strongest risk factors for dementia, the prevalence of dementia will likely increase. This thesis explores pathophysiological hallmarks of Alzheimer’s disease and vascular events as well as risk factors associated with dementia development in older individuals. In study I, we explored the prevalence of dementia in the oldest old and the relationship between stroke, transient ischemic attack, and dementia. We found that dementia was very common in the oldest old, and prevalence of dementia was higher in women than in men. However, in this unique group of oldest old, the association between stroke and development of dementia diminished. In study II, we explored biological markers of Alzheimer’s disease in relation to mortality. Alzheimer’s disease has measurable pathological biomarkers in the cerebrospinal fluid (Aβ42 and T-tau). The levels of these pathological biomarkers in 85-year-olds was associated with survival. In study III, we compared two cohorts of 85-year-olds born 22 years apart. We found that 85-year-olds examined between 2008 and 2010 had lower blood pressure than 85-year-olds examined 22 years earlier. In both cohorts, participants with dementia had lower blood pressure than those without dementia. In study IV, we investigated whether high blood pressure was associated with brain atrophy in Alzheimer’s specific brain regions. We found that hypertension in 70-year-olds without dementia was related to atrophy in brain regions often affected in Alzheimer’s disease, and atrophy was more widespread in those with longer duration of hypertension. In summary, this thesis presents common risk factors for dementia and further investigates hallmarks in Alzheimer’s disease with the aim to contribute to better understanding of Alzheimer’s disease and vascular dementia.