Lung disease hits 25% of long-term smokers

After 25 years of smoking, at least one in four people who do not quit will develop incurable lung disease, a long-term Dutch study suggests.

Chronic obstructive pulmonary disease causes airways in the lungs to become inflamed and obstructed, causing coughing or shortness of breath. The two major forms of the disease are chronic bronchitis and emphysema.

More than 714,000 Canadians have been diagnosed with COPD or more than two per cent of the population, according to the Lung Association of Canada.

Dr. Peter Lange of Hvidovre Hospital in Denmark and his colleagues monitored the lung health of 8,000 men and women between the ages of 30and 60 for 25 years.

More than 5,000 of the people were smokers and just over 1,200 were ex-smokers.

A quarter of the smokers who initially showed no symptoms developed COPD, and up to 40 per cent had some signs of the disease, the researchers report in this week's online issue of the journal Thorax.

"Our main finding is quite simple," the researchers wrote. "The longer people smoke, the higher the risk of developing COPD."

Benefits of quitting

Over the course of the study, 2,900 people died, including 109 from COPD.

The risk of COPD plummeted among those who quit soon after the study started, and none of the ex-smokers developed severe COPD. "Quitting smoking does make a substantial difference," the researchers said.

"The message is that many smokers develop airway obstruction if they live long enough and continue to smoke, and that the number that do so is increasing," Dr. Nick Anthonisen of the University of Manitoba Respiratory Hospitalsaid in a commentary accompanying the study.

"An argument can be made therefore that many, perhaps most, smokers are 'susceptible' to COPD if they live long enough."

The World Health Organization estimates COPD will becomes the third-largest cause of death worldwide by 2020.