Apathy and cognitive decline in clinical studies of older persons

This thesis consists of several clinical studies of which the overarching theme is apathy and cognitive decline in older persons. Cox analyses were used to study relationships between subjective memory complaints and two simple memory task scores with future dementia. A combination of tests that can be administered in about ten minutes, proved useful for identifying older persons in primary care at increased risk for dementia. Again using cox analyses, the second study showed that both apathy and depression symptoms, independently and in isolation, are associated with future dementia, although the associations are stronger for apathy symptoms. Subsequently, network analysis was used to dive deeper into the complex relationships between apathy, depression, functional disability, subjective memory complaints and future dementia. Using this novel method, associations between individual network items could be found while controlling for relations between other items. Then, in a prospective cohort study, the course of post-stroke apathy in relation to cognitive functioning was investigated with linear regression models. It was concluded that apathy and cognitive decline after stroke may need separate monitoring and treatment in rehabilitation programs for stroke survivors. Finally, information loss as a result of processes to recode variables was studied, an initiative often taken to pool data from clinical trials. By fitting linear regression models on data from three randomized controlled trials and on simulated data, it was found that information loss is most prominent for variables that have been recoded from continuous to discrete, which may impact subsequent in-depth pooled analyses.