Inside or Outside, Air Quality Affects COPD Symptoms

ABERDEEN, Scotland, Aug. 31 -- COPD patients may be as much at risk from air pollution inside their homes as they are outside, researchers found.

Fine particulate pollution levels in the homes of COPD patients reached on average of up to four times higher than the maximum recommended by the U.S. Environmental Protection Agency, in a study reported in the Sept. 1 issue of the American Journal of Respiratory and Critical Care Medicine.

The higher levels-mainly from secondhand smoke-were significantly linked to greater symptom burden (P

Interestingly, particulate matter had a stronger effect on symptom burden of current smokers than of nonsmokers as reflected in larger regression coefficients.

Thus, a 10-fold reduction in average particulate matter would be expected to reduce symptoms by 11.1 points in smokers versus 4.9 points in nonsmokers, and the change in particulate matter needed to produce a clinically significant four-point change was correspondingly smaller among smokers.

But, "the apparently greater effect among smokers may be an artifact of the higher levels of PM_2.5 in their homes," Dr. Osman and colleagues wrote.

Two other components of indoor air pollutant, endotoxin and nitrogen dioxide, were measured in participants' homes. However, neither was a significant predictor for any of the outcomes evaluated.

Further research is needed to test the long-term impact of indoor air quality on COPD patients as well as to determine whether indoor pollutant exposure increases frequency of exacerbations, the investigators said.

The authors also pointed out that the study was cross-sectional in design and health status was related to indoor environment measurement taken at one point in time.

But even though researchers could not prove causality, "because they used an objective measure of secondhand smoke exposure, these results provide strong new evidence linking secondhand smoke with worse COPD health status," Dr. Eisner concluded.