PhD defence J.M. (Mark) Noordzij

Summary:

In 2017, there were an estimated 962 million people aged 60 years or older worldwide, accounting for around 13% of the total population. This part of the population is growing at an annual rate of about 3% and increasingly lives in cities. The combination of urbanization and ageing can lead to new public health challenges, such as a higher risk of mental disorders and physical inactivity, but can also offer opportunities for the implementation of policies and interventions that promote public health. The city has therefore become a key site for the implementation of prevention and early identification policies on the trajectories of ageing and mental well-being. However, the implementation of such policies requires a good understanding of how the urban environment relates to health and well-being.

Empirical studies linking urban-environmental exposures to health outcomes rely on some amount of variation in exposure measures between the units of analysis. Variation in exposure levels can be the result of variation between urban environments, such as different neighborhoods, or variation within urban environments over time. However, many studies linking urbanenvironmental exposures to health-related outcomes are often limited to just one city or one, cross-sectional, measurement. Potential strategies to increase variation are to include multiple cities from different countries or to include multiple measurements taken over time.

The aim of this thesis was to explore the variation in urban environments and how it relates to physical activity and mental well-being by using data from different European cities. The overall aim of this thesis was further detailed in three, more specific, research aims:

• Research aim 1: To explore variation in physical urban-environmental exposures between cities and within cities over time.
• Research aim 2: To explore how physical urban-environmental exposure measures can be harmonized and applied within health research.
• Research aim 3: To investigate the extent to which variation in urban physical-environmental exposures between cities or over time relates to mental health and walking and cycling.