Study finds link between low neighborhood walkability and childhood asthma

Children living in neighborhoods that are not conducive to walking are more likely to develop asthma and to continue to have this condition through later childhood, according to a new study published in the Annals of the American Thoracic Society.

In "Associations Between Neighborhood Walkability and Incident and Ongoing Asthma in Children," researchers from Toronto's Hospital for Sick Children (SickKids) and the University of Toronto evaluated associations between home neighborhood walkability and both the incidence of asthma and its ongoing occurrence.

Although there have been studies of neighborhood walkability and chronic diseases such as diabetes in adults, this large, long-term study is believed to be the first to look at walkability and childhood asthma.

"We found that children living in neighborhoods with low walkability were more likely to develop asthma and to continue to have asthma during later childhood," said lead author, Dr. Elinor Simons, a pediatric allergist and clinician scientist who now works at the University of Manitoba and Children's Hospital Research Institute of Manitoba, Canada. "These findings show a relationship between lack of day-to-day physical activity or sedentary lifestyle and development of new and ongoing asthma in Toronto children."

Dr. Simons and colleagues used healthcare data housed in the province of Ontario's Institute for Clinical Evaluative Sciences (ICES) to follow 326,383 Greater Toronto children born between 1997 and 2003 until ages eight through 15. Asthma diagnoses were based on the time the children's data were entered in the validated Ontario Asthma Surveillance System (OASIS), which requires two outpatient visits within two consecutive years or any hospitalization for asthma. Children with asthma in OASIS were followed continuously starting at their time of diagnosis and until the end of the study.

A Walkability Index was used to examine whether the neighborhoods in which these children lived were conducive to walking. Neighborhood characteristics that comprised the index included population density, dwelling density, access to retail and services, and street connectivity.

The researchers used two statistical models to determine associations between asthma and walkability: associations between walkability and incident asthma were examined using Cox proportional hazards models, while associations between ongoing asthma and walkability in each year were determined with generalized linear mixed models.

The authors found that 69,628 children (21%) developed incident asthma and were followed in the OASIS database. Low walkability in a child's neighborhood of birth was associated with an increased risk of asthma development. Among children with asthma, low walkability in a given year was associated with greater odds of ongoing asthma in the same year. The median age of asthma diagnosis was 2.5 years for all children with asthma and 3.5 years for children who had ongoing asthma until the end of the study.

The same results were found after accounting (controlling) for gender, preterm birth, neighborhood income, obesity and allergic conditions.

The authors noted that their findings document a "statistically robust longitudinal association between childhood asthma and low neighborhood walkability, extending the results of previously published studies that have demonstrated variable associations between childhood asthma and exercise or sedentary lifestyle. These results also support community-level interventions to modify home neighborhood environment in ways that are associated with positive changes in individual physical activity levels."

"Toronto has a population of over six million multiethnic inhabitants, making it representative of many large urban centers in industrialized countries," said the study's authors. "Other large cities may have neighborhood walkability patterns that are similar to Toronto's, and may see similar associations with childhood asthma."

But how can neighborhood walkability be improved? It can be improved, for example, "By greater placement of services such as grocery stories within residential neighborhoods and adding pedestrian paths between roads to improve street connectivity," the authors said.

She added: "It is important to note that this study measured physical characteristics and did not look at social characteristics such as neighborhood crime and safety or cultural reasons for walking rather than using another means of transportation. These characteristics also need to be studied and taken into account."​