Mapping the links between city living and dementia

About a decade ago, on a visit to Croatia to see her parents, Ester Cerin noticed something different about her mother. 

“I noticed that her memory was failing her – she couldn’t remember simple things and was having trouble with simple tasks,” she recalls. 

As an experienced psychologist and statistician, Professor Cerin recognised the signs. 

“I took her to the doctor and I said, ‘I think my mum has dementia – she’s not functioning, et cetera, et cetera …’ They diagnosed her pretty soon after that.”  

Over the following years, Professor Cerin visited Croatia several times before her mother’s death. The experience of seeing her condition worsen with every visit was distressing, as it is for most people whose family members are diagnosed with dementia.   

“Having that lived experience of seeing the decline of a person you love, and also how much my dad suffered as well, it was very upsetting,” says Professor Cerin, an internationally recognised researcher specialising in environmental and psychosocial determinants of health. 

“I’m a psychologist, so of course I’ve always been interested in cognition and behaviour in one way or another, but witnessing my mother’s decline gave me extra motivation to broaden my research to encompass cognitive health. 

“I started to get really interested in understanding and investigating the links between this disease and our urban environments. I wanted to see how I could help.” 

Exploring the links 

Dementia is a significant health issue for many older people, with almost half a million Australians and some 40–50 million people globally suffering from the condition. 

In recent years, a growing body of research has explored the effects that city living can have on dementia and other types of cognitive decline.  

Observational studies have shown that factors like urban density and walkability, access to green space, and exposure to air and noise pollution can have either positive or negative effects on brain health. 

Conclusively linking one factor to one outcome is, however, notoriously difficult. 

“One of the issues we often have with research on urban environments and cognition is that it focuses on specific environmental factors – air pollution, for example – without taking into account other environmental factors that may also affect cognition and may confound the relationship,” says Professor Ester Cerin, who leads the Behaviour, Environment and Cognition Research Program at ACU’s Mary MacKillop Institute for Health Research.

“Let’s take the example of walkability. Experts like myself and my colleagues often talk about the benefits of walkable cities – ‘Oh, our cities need to be walkable environments for health and sustainability’ – and there’s no doubt that it has many benefits. 

“At the same time, walkability requires a certain level of population density, and with density comes pollution. So if you just focus on pollution and disregard everything else, you don’t get a clear picture because the positive effects of things like walkability may, or may not, offset the negative effects of pollution.”

A bold endeavour 

The reason that most research in the area doesn’t consider these confounding factors is that it’s a complicated undertaking. 

But a group of leading public health experts has risen to the challenge. Since 2019, they’ve been exploring how a wide range of characteristics of urban environments might influence cognitive decline, in world-first study that aims to give researchers a clearer picture of the issue. 

Led by Professor Cerin, the International Mind, Activities and urban Places (iMAP) study involves middle-aged and older people in three global cities – Melbourne, Barcelona and Hong Kong – investigating how their neighbourhood and the places they visit interact with lifestyle to impact brain health and psychological function. 

“This is quite a bold study because it’s trying to do a lot,” says Professor Cerin, who notes that the project involves some of the world’s leading urban health researchers, including Professor Mark Nieuwenhuijsen, who heads up the Air Pollution and Urban Environment Program at Barcelona’s Institute for Global Health and is a research professor at ACU, and Professor James Sallis, an ACU professorial fellow who is also a Distinguished Professor Emeritus at the University of California, San Diego.

“With all of our subjects across our three cities, we’re looking at multiple environmental factors and multiple lifestyle behaviours, and that’s really important because otherwise we’re left with a very skewed picture of the effect that urban environments can have on cognitive health. 

“We cannot pretend things are simple when they aren’t. If we’re able to get a clearer and fuller picture of how these different elements of urbanisation influence and impact cognitive health, we can ultimately use that information to develop recommendations to planners and policymakers, and hopefully guide decisions about what must change in order to create healthier and more sustainable cities.”

Expanding the knowledge base

The three cities involved in the iMAP study have diverse characteristics, with varying levels of urban density, green space, walkability and traffic-related air pollution. 

The inner suburbs of Melbourne, for example, have good pedestrian networks, with many parks and high walkability; however, many other parts of the city are characterised by urban sprawl. 

Conversely, urban areas in Hong Kong have the highest population density in the world, with corresponding high levels of air pollution. 

Barcelona sits somewhere between the two in terms of not only urban density and pollution, but also other factors like lifestyle, diet and the genetic make-up of its inhabitants – all vital factors in the prevalence of dementia. 

“So if we take Barcelona as an example, they have a Mediterranean diet and many have the APOE e2 gene, which reduces the risk of Alzheimer’s disease,” says Professor Cerin, who heads up the Melbourne portion of the project.

“In Hong Kong, many adults have only primary education and there are high levels of air pollution – and yet, it appears that cognitive health of people living there is generally better than in Melbourne, and these are good examples of the importance of accounting for all the different factors that contribute to conditions like dementia.” 

At all three sites, each study participant is monitored for physical, social and cognitive lifestyle activities and exposure to risk factors like air pollution. They’re also tested for cognitive and physical function, and assessed to determine levels of brain connectivity, cardiovascular disease and neurodegeneration. 

Says Professor Cerin: “This is a multifaceted study, in that we’re exploring the many positives and negatives of the urban environment, down to things like the effect that exposure to noise can have on sleep quality, the quality of social networks and relationships, and how genetics can affect cognitive decline. So the picture is complex, but we’re trying to depict the real world and how it works, and that realistic picture will help us to better understand how urban environments influence cognitive health.” 

The researchers expect to complete the project by 2024, with interim findings presented in 2023. In the future, they hope to expand iMAP to more global cities, with a view to including places in North America and South America, and other parts of Europe and Asia. 

The overall goal of the project, says Professor Cerin, is to guide the decisions that lead to healthier urban communities in the decades to come. 

“The big picture goal is to expand the evidence base on the relationship between the built environment and things like cognitive health and active living, so that we can provide the information that helps to create cities that are better for people and better for the environment,” she says.  

“For me personally, I guess it’s about making a positive contribution in an area that means a lot to me. I couldn’t help my mother – it was too late. But I can do something to help others, because this is a terrible disease.” 

Professor Ester Cerin is one of the world’s leading researchers on the environmental and psychosocial determinants of lifestyle behaviours and health across the lifespan. Before joining ACU, she worked across Australia, the USA and Hong Kong.

Learn more about the International Mind, Activities and urban Places (iMAP) study. 

Learn more about ACU.