THURSDAY, Oct. 21 (HealthDay News) -- A new study from Denmark says long-term exposure to low levels of air pollution could increase the risk of developing severe chronic obstructive pulmonary disease (COPD).

Previous research has found a link between high levels of air pollution and exacerbation of COPD, but this study connects long-term air pollution exposure to the development or progression of the lung disease, according to the researchers.

"Our findings have significance on a number of levels --- patients, primary care physicians, pulmonologists and public health officials should take note," lead researcher Zorana Andersen, a post-doctoral fellow at the Institute of Cancer Epidemiology of the Danish Cancer Society in Copenhagen, said in an American Thoracic Society news release.

Andersen and colleagues analyzed data to compare air pollution exposure and COPD incidence among more than 52,000 people, ages 50 to 64, who lived in Copenhagen and Aarhus (the two largest cities in Denmark). They found a "significant" association between long-term exposure to low levels of air pollution and COPD, even after they accounted for smoking status and other factors that affect COPD risk.

The association was strongest for people with diabetes and asthma and was slightly stronger for men, obese people, and those who ate less than 240 grams (about 8 ounces) of fruit per day.

"These results are in agreement with those of other cross-sectional studies on COPD and air pollution and longitudinal studies of air pollution and lung function. [They] strengthen the conclusion that air pollution is a causal agent in development of COPD," Andersen said.

The study appears online ahead of print in the American Journal of Respiratory and Critical Care Medicine.

More information

The American Academy of Family Physicians has more about COPD.