Researchers compared the household presence of cockroach, mouse, cat, dust mite and other allergens in neighborhoods with a high prevalence of asthma to that in low-prevalence neighborhoods. They found that cockroach, mouse and cat allergens were significantly higher in homes located in neighborhoods where asthma is more common and that children in these higher-exposure homes were more likely to be sensitized to cockroach antigens.
Source: ScienceDaily