Emphysema is less severe in black smokers than in their white counterparts, researchers reported on Monday.

This suggests that blacks respond differently to cigarette smoke or that genetic and environmental factors may slightly alter their lung structure, the researchers said.

“This data may give us some clues to hone in on how emphysema develops,” said Dr. Wissam Chatila, lead author on the study to be published in the journal Chest.

Researchers have long known that emphysema is the only smoking-related disease less common among blacks than whites. This study showed that when blacks develop the disease, it is also distributed differently in their lungs, the researchers from the Temple University School of Medicine said.

Emphysema is a chronic lung disease characterized by the destruction of lung tissue or the loss of its elasticity.

White emphysema patients are more likely than blacks to have damaged tissue in the upper parts of their lungs, according to the X-rays of 64 patients enrolled in the National Emphysema Treatment Trial, the researchers said.

In spite of this, other medical exams showed that the breathing of the black emphysema patients was just as debilitated as the whites, possibly due to factors other than the disease, the researchers said.

“This indicates that there must be something else going on,” senior author Dr. Gerard Criner said.

His team has speculated that genetics and environmental factors may cause African Americans to develop smaller airways in their lungs, making them more prone to bronchitis and other lung obstructions.

This might explain why - even with less severe cases of emphysema - they continue to score poorly on exams measuring lung function and exercise ability.