Healthy aging and longevity are influenced by the individual's health and life span. However, both are complex mechanisms, which is why we see differences in cognitive decline, even in the absence of neurodisorders. Moreover, we know there are medical situations where advanced age is a predisposing factor, and long-term cognitive impairment is one of the complications of, for instance, delirium. 

This thesis aims to investigate the common mechanism of the functional deterioration of network function between normal aging subjects without clinical symptoms of cognitive decline and study early functional changes related to delirium that can lead to cognitive decline after severe septic encephalopathy, primarily with EEG technics.

In the first two papers, I examined whether cEEG could be a potential tool for diagnosing and predicting delirious episodes in critically ill patients and whether quantitative cEEG is better than standard qualitative analysis. 

The main results were: I) Using qualitative analysis, preserved cEEG high-frequency activity and EEG reactivity were the most robust markers of the absence of delirium. II) In the quantitative cEEG analysis, mean global field power and lack of EEG reactivity predicted delirium. III) Low global coherence predicted delirium. 

The third paper investigated how brain network activity and structure were related to cognitive function and how life course factors and current health impacted the relationship. The main results were I) Course of intelligence affects the relationship between the hippocampus and global cognition. II) EEG markers suggest that total power is positively associated with cognition and years of education. III) Early life factors, particularly education, are essential for preserving cognition. ​

Martin Lauritzen, 

Henrik Bo Wiberg Larsson 

Krisztina Benedek