Researchers found that among more than 2,000 Chicago children age 9 or younger, those from neighbourhoods with moderate to serious problems with violence were about 60% more likely to develop asthma in the next few years than children from less violent neighbourhoods.
The association was not explained by factors like race, family income, or other neighbourhood characteristics, like the overall levels of poverty and unemployment.
This suggests that something about exposure to violence, itself, may influence children's asthma risk, according to the researchers, led by Dr. Michelle J. Sternthal of the Harvard School of Public Health in Boston.
The findings, published online in the European Respiratory Journal, are based on interviews with parents of 2,071 Chicago children, conducted three times over six years. More than 80% were African American or Hispanic.
At the second interview, parents were asked about neighbourhood violence - specifically, how many times their child had ever seen someone physically assaulted or attacked with a weapon, or heard a gun shot. At the third interview, parents were asked whether their child had ever been diagnosed with asthma.
Overall, Sternthal's team found, two-thirds of children in the study had been exposed to at least moderate levels of neighborhood violence, while 19 percent had been diagnosed with asthma.
Asthmatic children were more likely than those without asthma to live in highly violent neighbourhoods.
Of children with asthma, 43% were from neighbourhoods with a high level of violence, according to the researchers. That compared with 32% of kids without asthma. And while 36% of non-asthmatic kids lived in neighbourhoods with little violence, that was true of only 22% of children with asthma.
When the researchers considered a range of factors that might explain the connection, neighbourhood violence itself remained linked to a higher asthma risk.
It is plausible, according to Sternthal's team, that exposure to community violence could affect kids' asthma development. Chronic stress, for example, may affect the nervous and immune systems in a way that increases the risk of inflammatory diseases like asthma.
Neighbourhood violence may also affect asthma risk indirectly - if, for example, it harms mothers' mental well-being and, along with that, their ability to care for their children.
In addition, kids in violent neighbourhoods may be unable to go outdoors and get exercise - which could, the researchers say, promote obesity, a risk factor for asthma.
It has long been known that asthma rates are higher-than-average in US inner cities, with factors such as air pollution and indoor allergens believed to play a role. If neighbourhood violence is in fact an asthma risk factor, Sternthal and her colleagues write, it could help explain the elevated rates of the disease in urban areas.
It would also mean that experts need to look beyond traditional health-related measures to combat asthma in inner cities, the researchers point out. Efforts to reduce neighborhood violence, they say, could have additional benefits for children's health.
How often does your child play outside?