Finland's prevalence of chronic obstructive pulmonary disease (COPD), a group of serious lung diseases closely related to smoking, has held relatively steady in recent decades, a new study finds.

The findings, researchers say, are in line with what has been seen in the nation's smoking trends.

COPD refers to a group of progressive lung diseases that includes emphysema and chronic bronchitis. They arise when damage to the lungs causes symptoms such as shortness of breath, chronic cough, chest tightness and wheezing.

Cigarette smoking is the most common cause of COPD, and the global impact of the disease is expected to increase, according to the researchers on the new study -- because worldwide, smoking continues to be a major problem and the elderly population in many nations is growing.

For their study, published in the European Respiratory Journal, the researchers compared the findings of two Finnish national health surveys, from 1978-1980 and 2000-2001, to see how the prevalence of COPD may have changed over time.

They found that the prevalence of COPD changed little among men and women over two decades.

Among men, 4.7 percent had some stage of COPD in the 1978-1980 study, based on tests of lung function. That figure was 4.3 percent 20 years later.

Among women, 2.2 had COPD in the earlier study, versus 3.1 percent in 2000-2001 -- an increase that was not statistically significant.

These findings conform well to the trends in smoking among men and women since the early 1970s toward the end of the century in this country, write the researchers, led by Dr. Vasankari M. Tuula of Turku University Hospital in Finland.

Among Finnish men, they note, the smoking rate peaked in the 1970s, reaching a high of 50 percent in some areas of the country. It has since gradually decreased, and stood at just above 30 percent in 1997.

Since COPD emerges as a long-term consequence of smoking, the benefits of this more recent decline in smoking would not yet have been apparent in 2000.

In contrast with men, Finnish women's smoking rates have increased over time -- from 10 percent in the 1970s to 20 percent in 2002, Tuula's team notes. Whether that trend will mean more cases of COPD among women in the future remains to be seen.

Not surprisingly, smoking was a key risk factor for COPD in both study periods and among both men and women. In 2000-2001, current smokers had six times the risk of COPD that never-smokers did, while former smokers had a three-fold higher risk.

The findings underscore the importance of quitting smoking, or preferably never starting, according to the researchers.

In the U.S., a 2008 government health survey found that 1.7 percent of adults living outside of care facilities had ever been diagnosed with emphysema. Just over 4 percent had been diagnosed with chronic bronchitis in the past year.

SOURCE: European Respiratory Journal, online August 6, 2010.