Young adults (ages 20 to 44) with normal lung function who later develop chronic cough and phlegm have a fourfold higher risk of developing chronic obstructive pulmonary disease (COPD).
The results of this 10-year respiratory study appear in the first issue for January 2007 of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.
Isa Cerveri, M.D., of the Division of Respiratory Diseases at San Matteo Hospital and University of Pavia in Italy, and 19 associates showed that the presence of chronic cough and phlegm among study participants was an independent and statistically significant predictor of COPD. Of the 5,002 individuals in the study cohort, 123 were diagnosed with COPD. All participants had normal lung function at baseline.
COPD is the fourth leading cause of death in the United States, killing 122,283 Americans in 2003. It results from chronic bronchitis and emphysema, two lung diseases which frequently co-exist and cause obstruction to airflow that interferes with normal breathing. Smoking is the primary cause of COPD.
"In a large international cohort of individuals from ages 20 to 44, the 10-year cumulative incidence of COPD was 2.8 percent," said Dr. Cerveri. "It was 4.6 percent in adults aged 40 to 44. This finding points out that COPD is a major health problem even in young adults who are usually not considered to be at risk. In agreement with previous research, we found that the progression toward airflow obstruction is a continuous and gradual process, where sudden changes are extremely unlikely."
Among the study group, about 77 percent of the 123 COPD cases were smokers. In the sample as a whole, about 55 percent smoked.
The authors noted their results confirm that, from a public health perspective, the prevention of smoking and smoking cessation are the most effective strategies to deter the occurrence of COPD and reduce its burden.
"Our results show that the presence of chronic cough and phlegm is not an innocent symptom, but is an early marker of airflow obstruction," said Dr. Cerveri.
In addition to cough and phlegm in participants, researchers considered such factors as sex, age, dyspnea (breathlessness), smoking habits and level of education. All participants received lung function tests and blood workups at the beginning and end of the study.
In an editorial on the research in the same issue of the journal, Jørgen Vestbo, M.D., of Hvidovre University Hospital in Denmark and the University of Manchester in the United Kingdom, wrote: "The virtue of the study by Drs. Cerveri and colleagues lies in its size and thus the ability to calculate estimates with acceptable reliability. In this respect, it adds to previous work from the same group and indicates that the statement '15 percent of smokers will develop COPD' is wrong and that lifetime risk of COPD in smokers is significantly higher, probably about 35 to 50 percent."
He continued: "The predictive value of chronic cough and phlegm is probably more surprising given the fact that this cohort was young and had normal lung function at baseline."
Dr. Vestbo concluded: "How does the study impact our understanding of the natural history of COPD? As recently reported in this journal, it has taken the respiratory community a painstakingly long time to do properly sized studies in young adults with sound methodology and state-of-the-art analysis. With COPD epidemiology growing in the European Community Respiratory Health Survey and other cohorts of young adults, we may get a better picture of early events in COPD---although our colleagues in pediatric epidemiology will probably continue to claim that we are still only looking at 'the elderly'!"