Longitudinal Associations between the Built Environment, Biological Aging and Cognition
This study utilizing multiple longitudinal cohorts found no consistent evidence that childhood exposure to the built environment is associated with biological aging or cognition during adolescence, suggesting these relationships may develop later in life.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
Cities are more than just collections of buildings and roads; they are complex environments that shape how we live, think, and grow. For decades, scientists have known that where we live affects our health, often linking city life to higher rates of stress or mental health challenges in adults. But a critical question has remained unanswered: does the concrete and density of a city affect the very biology of a child's body and mind while they are still developing? To investigate this, researchers have turned to new ways of measuring time. Instead of just counting the years a person has lived, scientists can now look at DNA to see how fast a body is aging biologically, or scan the brain to see if it looks older or younger than its calendar age. These measures act like a biological clock, ticking faster or slower depending on life's experiences. Understanding whether the built environment—everything from population density and traffic to the amount of green space—speeds up or slows down these clocks during childhood could reveal a powerful window for preventing future health problems.
A team of researchers set out to test this idea by looking at thousands of young people across three different long-term studies in the United Kingdom and the Netherlands. They wanted to see if the type of neighborhood a child lived in at age twelve had any lasting impact on their biological age, their brain development, or their thinking skills as they moved into late adolescence and early adulthood. The team focused on a composite picture of the built environment, combining factors like how crowded an area is, how connected the streets are, and how much green space is available, rather than looking at just one feature in isolation. They tracked these children over many years, checking their DNA, scanning their brains with magnetic resonance imaging, and testing their cognitive abilities at different stages of life.
The results were surprisingly clear: the researchers found no consistent evidence that the built environment a child experienced at age twelve had a measurable effect on their biological aging or brain age later on. When the team analyzed the DNA of over 2,400 young adults, they found no link between the urban or rural nature of their childhood home and how fast their biological clocks were ticking. Similarly, when they examined brain scans from hundreds of participants, the data showed no connection between childhood neighborhood characteristics and whether a brain appeared older or younger than expected for its age. In short, the concrete density or greenery of a child's neighborhood did not seem to accelerate or decelerate their biological aging during these formative years.
The findings regarding thinking skills were more mixed, but still pointed toward a lack of a simple, universal rule. In one large group of participants, the researchers found no link between the built environment and cognitive performance. However, in a second group from the Netherlands, a different pattern emerged: children who grew up in more urbanized areas showed slightly lower scores on general cognitive tests. Yet, when the researchers tried to confirm this specific finding in a third group of British children, the link disappeared. This inconsistency suggests that if there is a connection between city living and how a young person thinks, it is not a straightforward cause-and-effect relationship. Instead, it likely depends heavily on the specific context, such as local differences in green space, the particular type of thinking being measured, or the time gap between childhood and the test.
The study also explored whether these environmental factors might be linked to specific types of biological aging, such as the pace at which a person's cells are aging, but again, no clear patterns emerged. The researchers noted that their ability to detect subtle effects might have been limited because most of the children in the studies already lived in urban settings, leaving little variation to compare. Furthermore, because the children were measured at only one point in time regarding their neighborhood, the study could not account for families moving or changes in the local environment over time. The authors suggest that the effects of the built environment on biological aging might simply take longer to appear, perhaps not becoming visible until much later in life, or that the relationship is too complex to be captured by a single measure of neighborhood type.
Ultimately, this research provides a necessary reality check for the field. While it is well established that adult health is tied to neighborhood quality, this study indicates that the biological mechanisms linking city living to aging and brain health may not be active or detectable during childhood and adolescence. The absence of a consistent signal across three large, well-designed studies suggests that we should be cautious about assuming that the concrete jungle of childhood automatically speeds up biological aging. Instead, the relationship between where we grow up and how our bodies and brains develop appears to be far more nuanced, potentially unfolding over a longer timeline or requiring different, more specific measurements to be understood. For now, the data tells us that the childhood built environment, as a broad factor, does not leave an immediate, measurable mark on the biological age or brain age of young people.
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