How do you feel today? The use of a Dynamic Systems approach in the conceptualization and analysis of Health Related Quality of Life in the older adults

The western world is facing a demographic revolution. The slowdown of the birth rate together with the increasing number of older adults generates a change in the population pyramid: a thinner basis (infants and children) carries an increasingly big peak (older adults). This provides a challenge for society: it becomes increasingly important that old people remain healthy and independent as long as possible. This study aims to generate knowledge to address this challenge. It focusses on the development of Health Related Quality of Life (HRQOL) as a central concept in the ageing process. HRQOL is a person-centered concept, referring to the social, physical and mental domain. The general aim of the thesis is to study the development of HRQOL from a dynamic systems approach in order to get insight in the developmental trajectories and their characteristics, and to analyze developmental trends in older adults. We developed a conceptual model of HRQOL. This model describes the development of HRQOL as an iterative process in which individual characteristics are assumed to affect the development in a complex and nonlinear way. As a next step, a mathematical model is developed based on the conceptual one. Such a model includes parameters that represent the relevant individual characteristics, and allows us to explore the possible developmental trajectories of different individuals in different conditions. First validation tests are promising, but much more validation is needed. Once validated, the model can be a big help in the development of interventions and guidance of the older adults.