Women more vulnerable to lung damage

HEALTH - Women may be more vulnerable to lung damage from smoking than men, according to new research.

In a study looking at chronic obstructive pulmonary disease (COPD), scientists at Brigham and Women's Hospital, part of Harvard University Medical School, and the University of Bergen in Norway found that female smokers experienced reduced lung function at a lower level of exposure and at a younger age than male smokers.

"There's an important public health message here," says senior author Dr. Dawn DeMeo, assistant professor of medicine at Harvard. "Many women believe their smoking is too limited to be harmful, that a few cigarettes a day is a minimal risk. Our research shows there's no safe amount, especially for women."

The study, presented yesterday at the American Thoracic Society conference in San Diego, analyzed data from Norway of current and former smokers, 954 of whom had COPD; 955 were controls.

The gender differences were most pronounced among COPD patients under the age of 60, considered early onset, and those who smoked less than a pack a day for 20 years, the low-exposure group.

COPD is a progressive disease characterized by increasingly difficult breathing. It is most often caused by cigarette smoking and includes the conditions emphysema and chronic bronchitis

Another study, also reported this month, looked at 683 lung cancer patients at a Swiss treatment centre. It found that women tended to be younger when they got cancer even though, on average, they had smoked less than the men, suggesting an increased susceptibility.

The findings were presented earlier this month at the European Multidisciplinary Conference in Thoracic Oncology in Switzerland.

Previous research has also indicated an increased female vulnerability. "The idea has been around for 10 to 15 years. The evidence is building up piece by piece," says Dr. Donna Stewart, chair of women's health at the University Health Network, in Toronto.

But no one knows why there might be a gender difference.

"One theory is that women have smaller lungs than men, so each cigarette does more harm," says Dr. Inga-Cecilie Soerheim, lead author on the COPD study.

Another possible explanation is that men and women metabolize cigarette smoke differently. An enzyme involved in metabolizing drugs and tobacco smoke is regulated by estrogen, Stewart explains. Genetic factors may also be at play.

Roberta Ferrence, executive director of the Ontario Tobacco Research Unit, is cautious about putting too much emphasis on gender differences.

"It's very difficult to figure out what's biological, genetic, environmental, behavioural. Even the type of cigarette and how it's smoked is part of it," she says.

"It's a complex mix. The bottom line is that everyone should quit and nobody should start," adds Ferrence.

In Canada, lung cancer is the leading cause of cancer death for both men and women.