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Asthma Linked to Cockroach Exposure
Childhood asthma rates in New York City neighborhoods range from 3 to 19%. A Columbia University study suggests that much of this variation may be due to the size of the local cockroach population.
A 2007 nationwide study by the NIH concluded that over half of all asthma cases were due to allergies. And while cockroaches may not be the whole story, in New York City, they certainly seem to be a large part of it.
The recent Columbia study found that children living in high-asthma neighborhoods had higher concentrations of cockroach allergens in their home. And they also were more than twice as likely to have cockroach-specific antibodies circulating in their blood. Cockroach-specific antibodies in the blood show that a person has been exposed to cockroaches and is sensitized to them. They indicate a possible allergy, but are not proof of one.
The researchers found that 23.7% of children living in high-asthma neighborhoods showed sensitization to cockroaches, more than double the 10.8% rate seen in low asthma neighborhoods. Their homes also had higher concentration of cockroach allergens, as well as allergens associated with mice and cats.
The researchers looked at 120 seven- to eight-year-old children living in high-asthma neighborhoods and 119 from low-asthma neighborhoods. Dust samples were collected from their beds and analyzed for the presence of specific allergens — cat, dog, mouse, dust mite and cockroach. Blood samples were also taken from the children and tested for antibodies to these allergens.
Because previous studies have linked poverty to asthma, the researchers only looked at children from families with the same middle-income health insurance plan.
While the study did find possible links between mouse and cat allergens to asthma, what stood out the strongest was the cockroach association.
Over half of the children in the study already had asthma. Those whose blood showed a sensitization to cockroaches or mice were more likely to have asthma.
Having a cat in the home was not associated with a higher asthma rate.
The study suggests that controlling cockroaches could lower the risk of childhood asthma. But spraying toxic insecticides can cause problems that are even worse. Sealing up cracks in the home and eliminating the insects' sources of food and water are a better strategy.
The New York City Department of Health website offers several tips for combating roaches. To see them, click here.
An article on the study was published online by the Journal of Allergy and Clinical Immunology on May 3, 2011. The article will also appear in a future print edition of the journal.
July 22, 2011