The neighbourhood where an individual lives may increase the risk of hospitalisation from respiratory diseases like Covid-19

The range of Covid-19 symptoms varies – some feel a mild cold, others are hospitalised, while others perish.

Many studies have linked the severity of Covid-19 symptoms with an individual’s biological factors, but less is known about the impact of non-biological factors, such as the environment in which people live.

The new study is the first to show that the neighbourhood-built environment might pose an independent risk in determining the individuals hospitalised due to Covid-19 illness.

The authors found that in a cohort of more than 18,000 individuals with SARS-CoV-2 infections, living in multi-family buildings, living in a neighbourhood with higher air pollution (PM2.5) levels and living in a neighbourhood with lower walkability and bike-ability were associated with a greater incidence rate of hospitalisation, even when controlling for socioeconomic vulnerability and individual-level demographic and medical characteristics.

Neighbourhoods with higher public transit quality and access were also associated with a higher incidence rate of hospitalisation.

The study identified differences between the two largest ethnic groups in the region.

Higher PM2.5 levels posed a higher rate of hospitalisation for Latinx individuals, and density and overcrowding showed stronger associations for non-Hispanic White individuals. 

The findings could help inform public health and urban planning initiatives in lowering the risk of hospitalisations linked to Covid-19 and other respiratory pathogens.

Alessandro Rigolon, associate professor at the University of Utah and lead author of the study, said: “For urban planners, the findings underline what we’re already trying to do to build healthier communities – create more walkability, bike-ability and infrastructure that will reduce air pollution.

“From a public health perspective, the findings can help testing and vaccination campaigns target areas with higher air pollution or multi-family housing.”

The study also exposed how urban policies from the past continue to impact the daily lives of many communities. 

Jeremy Németh, professor at the University of Colorado Denver and co-author of the study, said: “We found much higher rates of Covid-19 hospitalisations along the I-25 and I-70 corridors and in the industrial areas of north Denver.

“These are the same areas that have experienced decades of disinvestment and increased air pollution due to racist land-use policies levied on our cities in the early 20th Century.”




Neighbourhood characteristics


The study analysed the neighbourhood characteristics in the Denver Metro Area associated with hospitalisations of 18,042 people who tested positive for SARS-CoV-2 between May and December in 2020, before vaccines became extensively available.

Researchers from two of the Denver Metro Area’s major healthcare systems, Denver Health and University of Colorado Hospital, reviewed more than 30,000 cases of eligible individuals.

They limited the cohort to those living in the greater metro area, and matched available health record data for each case.

Variables pulled from the medical record included age and body mass index (BMI), evidence of tobacco use, hypertension, chronic lung disease, some forms of cardiovascular disease and chronic kidney disease.

Researchers at the University of Colorado Denver then converted addresses of people in the final cohort to their geospatial co-ordinates and assigned environmental variables accordingly. 

Ethical oversight and approval for the study was granted by the Colorado Multiple Institutional Review Board and all protected health information was anonymised prior to sharing. 

Rigolon said: “Very few studies are comprehensive like ours. We’re able to control for some individual-level factors that, for people with Covid-19, would lead to higher chances of being hospitalised.”

With biological factors largely accounted for, the authors identified four characteristics of a neighbourhood that might contribute to Covid-19 hospitalisation: density and overcrowding, including living in an overcrowded home or multi-family building; environmental hazards, such as air pollution levels (PM 2.5) and proximity to highways; environmental amenities, including access to parks; and mobility options, including public transit access, walkability and bike-ability.

The authors were unsurprised that individuals with compromised lung and immune systems who face chronic air pollution would be unable to respond as well to the respiratory disease and would be more likely to need hospitalisation after contracting Covid-19.

Their finding that higher PM2.5 levels impacted Latinx individuals more than non-Hispanic White individuals underscores a worldwide problem – air pollution disproportionately affects People of Colour.


Future planning


While findings support making existing neighbourhoods more walkable and bikeable, the authors emphasised that future planning efforts to reduce emissions should centre the principles of environmental justice.

Since walkability was particularly protective in Latinx communities, the authors suggest that cities should prioritise investing to make Latinx-dominant neighbourhoods pedestrian-friendly.

The result for density and overcrowding underscore the need for vaccination and testing efforts to focus on areas with multi-family housing to mitigate risk of severe disease.

Because living in transit-rich neighbourhoods was associated with higher risk of hospitalisation from Covid-19, public health measures like educational campaigns and outreach in these areas are particularly important. 

Sarah Rowan, associate professor of medicine at University of Colorado School of Medicine, Denver Health infectious diseases physician and the study’s senior author, said: “So many health disparities track along geographic lines.

“We’ve long suspected that more than just pre-existing medical conditions were to blame for the disparities.

“It was interesting to work with the urban planning teams to pinpoint exactly which environmental factors were partially to blame for disproportionate rates of hospitalisations that we keep seeing.

“This will help public health leaders continue to advocate for healthier cities, and it helps inform outreach efforts to address Covid-19 and other respiratory illnesses.”

The study is published in PLoS ONE.

Image 1: The Denver Metro Area which includes housing, freeways, railways and the downtown core. Credit: Paul Wedlake/ University of Colorado Denver (CC BY-NC-SA).

Image 2: Density of SARS-CoV-2 cases and hospitalisations in the study area (Denver metropolitan area) and the City of Denver. Credit: Rigolon et al, (2023) PLoS ONE (CC BY-NC-SA).

Research Aether / Health Uncovered