(HealthDay News) -- A new study finds that at least 1 in every 4 smokers will develop progressive and incurable chronic obstructive pulmonary disease (COPD), a much higher risk than previously believed.
COPD is a respiratory disease that results in blocked air flow to the lungs and grows progressively worse.
For this study, published online in the journal Thorax, researchers at Hvidovre Hospital analyzed data on 8,000 men and women, ages 30 to 60. All were monitored for 25 years as part of the Copenhagen City Heart Study.
At the start of the study, all the participants' lungs were healthy and working normally. However, over the course of the 25 years, the lungs of almost all the male non-smokers continued to function normally, compared to 60 percent of men who continued to smoke.
Among women, 90 percent of non-smokers still had healthy lungs at the end of 25 years, compared to 70 percent of smokers.
Overall, 25 percent of the participants developed moderate or severe COPD over the 25 years. Persistent smokers were six times more likely to develop COPD than non-smokers.
During the 25 years, there were 2,900 deaths in the study group. Of those deaths, 109 were directly attributable to COPD, and nearly all those deaths were in people who were active smokers at the start of the study. Only two non-smokers died of COPD.
The study also found a sharp decline in the risk of COPD among people who stopped smoking soon after the start of the study. Over the 25 years, none of these ex-smokers developed severe COPD.
The U.S. National Heart, Lung, and Blood Institute has more about COPD.