PhD defence J.L. (Jendé) Zijlmans

Summary:

Background: Cognitive and brain reserve aim to explain individual differences in susceptibility to dementia. In this thesis, I investigated determinants and outcomes of cognitive and brain reserve in middle-aged and elderly persons in the population.

Methods: The studies in this thesis are conducted within the population-based Rotterdam Study and the population-based ORACLE study. First, I investigated which sociodemographic, lifestyle, physical, and psychosocial determinants are associated with cognitive reserve (Rotterdam Study). Thereafter I investigated cognitive and brain reserve in relation to dementia, early mortality and late-life depression (Rotterdam Study). Finally, I investigated long-term outcomes of traumatic brain injury (ORACLE study).

Results: I found that smoking, lack of paid employment, alcohol use, diabetes mellitus, history of cancer, chronic obstructive pulmonary disorder, depressive symptoms and longer sleep onset latency were associated with cognitive reserve, but with clear differences between men and women. Additionally, I found that higher cognitive and brain reserve were not only associated with a lower risk of dementia, but also with a lower risk of mortality and late-life depression. Finally, I found that traumatic brain injury with loss of consciousness was associated with mid-life subjective memory complaints, but not with cognition or brain-MRI outcomes.

Conclusions: With this thesis, a first step has been taken towards identifying risk and protective factors of cognitive reserve, and identifying cognitive and brain reserve as factors that can not only influence the risk of dementia, but also mortality and late-life depression.