A study by researchers at the Harvard School of Public Health has shown strong evidence of adolescent lung damage from cigarette smoking.

The study, encompassing 10,000 adolescents ages 10 to 18 years old, found smoking obstructs airways and slows the growth of lung function in adolescents.

In addition, the study showed that even low levels of smoking can be harmful to adolescents.

"Now we also find that smoking as few as five cigarettes per day can reduce lung function growth of both boys and girls during adolescence," the study's lead author, Diane Gold, said in a statement.

Although previous studies have had similar results, this study is "by far, the largest study that has been done on adolescent smoking" according to James H. Ware, Mosteller professor of biostatistics at the School of Public Health and a co-author of the study.

The study also provided the most conclusive connection between smoking and adolescent lung damage.

"This paper shows more definitively that from the early stages of smoking there are already discernible effects on the rate of growth on the lungs in adolescents," said Associate Professor of Medicine Douglas W. Dockery, another co-author of the study.

The report also revealed a difference between the effects of smoking on girls and boys.

"We find that girls in the teen years may be particularly vulnerable to these cigarette effects," Gold said in the statement.

"By age 18, teenage girls who do not take up smoking are likely to reach and maintain a higher maximal lung function while those who smoke may begin an early decline in their lung function," said Gold, who is assistant professor of medicine at School of Public Health.

At each level of smoking, rates of wheezing were greater among girls. The reason for the difference between the boys and girls could be the inherent smaller size of the air passages in females, although researchers said that has not yet been determined. Ware said hormonal interactions could also play a role in the differences in effect on males and females.

Authors said the study has significant long term implications.

"After about age 20 to 25, one starts losing lung function irreversibly at a rate of 1 percent per year in a nonsmoker," Dockery said. "If you have things that accelerate loss, this puts you at greater risk of developing emphysema and other pulmonary diseases."

The study, published in the September 26 issue of the New England Journal of Medicine, followed 5,000 boys and 4,900 girls between 1974 and 1989. Researchers tracked the actual development of lung function among individuals including smokers and non-smokers.

The tests were performed in Watertown, Mass.; Kingston, Tenn.; Steubenville, Ohio; Portage, Wis.; St. Louis, Mont.; and Topeka, Kan., as part of an air pollution study.

Lung function was determined annually using a spirometer, which measures the volume of air exhaled and the rate at which it is exhaled.

Other co-authors of the study include Research Fellow Xiabin Wang, Associate Professor of Biostatistics David Wypij and Kass Professor of Medicine Frank E. Speizer.