Household Conditions Combine to Aggravate Asthma

A study of more than 400 adults with asthma and rhinitis has found that their home indoor environment is strongly linked to how well their lungs function, how healthy they are, and the severity of their disease
 
The study, headed by COEH faculty member Paul Blanc of UCSF, examined many of the factors in households that are presumed to aggravate asthma and rhinitis. Rhinitis is a reaction to irritants like pollens in the air and causes sneezing, congestion, runny nose, and itchy eyes, nose, and throat. Among common household conditions included in the study were dust mites in the bedroom, mold on damp walls and mildew in the bathroom, nitrogen dioxide from stoves, and the presence of cats or dogs.

In contrast to most studies, which focus on the impact of exposure to just one aspect of the home indoor environment, Blanc and his team investigated the impact of exposure to a combination of risk factors.

Blanc’s team conducted extensive interviews, visited more than 200 homes, analyzed dust and air samples from these homes, analyzed blood samples and measured participant’s lung function. The researchers found that it was the combined effects of a variety of indoor environmental exposures that explained a lot of the variability in the lung function and health status of the study participants (10–24 percent of the variance, depending on the combination of exposures). No single factor in isolation had a strong effect on health outcomes.

“Our study underscored that the home indoor environment is every bit as complex as the outdoor environment,” Blanc said. “We need to look at combinations of risk factors together and not simply hang our hats on whether people have pets, or whether there is mold in the house, or whether they use gas heaters, or whether there is environmental tobacco smoke. We found that factors that may be low level individually can have a more powerful health impact when acting together. For example, a combination of environmental factors may explain why one person has worse lung function than another, even though they both have similar asthma.”

For doctors, the study underscores how important it is to understand what a patient’s home environment is like, Blanc said: “Taking an environmental history becomes as important as taking an occupational history.”

Blanc and his colleagues are continuing to follow the study participants beyond the household to learn more about the impact that factors in the outdoor and work environments may have on their health over time. Blanc hopes this research will eventually help to improve the quality of life for people with asthma and rhinitis.

Other COEH faculty members and affiliates involved in the home indoor environment study include John Balmes, Mark Eisner, Patricia Quinlan, and Edward Yelin of UCSF, and Katharine Hammond of UC Berkeley.