Chronic obstructive pulmonary disease, commonly called "smoker's cough," is killing more and more nonsmokers and new studies show that indoor pollution is just as much to blame for the problem as outdoor pollution.

More than 2.5 million people die each year from COPD, about as many who die annually from AIDS. Allergies, tuberculosis and poor ventilation can cause the disease, the fifth-leading cause of death in high-income countries, according to a study published this week in the Lancet.

"COPD is much more common than previous estimates would suggest," said study author Dr. A. Sonia Buist, chief of the division of pulmonary and critical care medicine at Oregon Health & Science University. "We did the study, because there is a huge disconnect between the public and the public health perception of the burden of COPD, and the reality."

For the study, researchers collected data on 9,425 people age 40 and older from 12 different countries.

They found that the overall prevalence of severe COPD, an umbrella term for numerous respiratory ailments including emphysema, was 10.1 percent in the U.S. and worldwide. Among men, it was 11.8 percent and for women, 8.5 percent.

The study found that one in 10 adults over the age of 40 suffered from advanced stages of COPD. The disease became more prevalent as people aged and was just as common among those who had never smoked as with those who had smoked for a certain period.

“If every smoker in the world were to stop smoking today, the rates of COPD would probably continue to increase for the next 20 years,” Buist and colleague David M. Mannino wrote in the journal.

Indoor Pollution Continued Problem

A study by Scottish researchers published in the September issue of the American Journal of Respiratory and Critical Care Medicine found that poor indoor air quality adversely impacts the symptoms of COPD.

While the exacerbating effects of outdoor pollutants on COPD patients have been well-documented, few studies have analyzed the impact of indoor air quality on COPD patients, researchers said.

COPD is the fourth-leading cause of death in the U.S., according to lead investigator Liesl M. Osman, Ph.D, who completed the study with a team of researchers in Aberdeen, Scotland

“Although exposure to outdoor pollution is important, most people spend the greater part of their time indoors,” wrote Osman in the article.

The study looked at 148 Scottish residents who displayed symptoms of mild to severe COPD.

All participants completed the St. George’s Respiratory Questionnaire (SGRQ) to assess their symptoms, activity limitation and the impact of their disease. Each subject was also asked about their current smoking status, which was verified by salivary cotinine levels.

The researchers found that indoor concentrations of particulate pollution in the subjects’ homes frequently exceeded standards for outdoor air. In at least one instance, the highest concentration of a home was more than 40 times that of the recommended maximum.

The indoor pollution appeared to affect smokers more than nonsmokers, but remains a concern for smokers and nonsmokers alike, the researchers said.