Inga-Cecilie Soerheim and her colleagues at Brigham and Women's Hospital and the University of Bergen in Norway studied 954 patients with COPD and 955 participants unaffected by the disease. Although the researchers found no overall differences between the genders when it came to the severity of COPD or lung function (in this case, measured by the volume of air a person could exhale in one second), they did find that affected women tended to be younger and had smoked less than men.
In both groups, the team found that women suffered from a more severe form of the disease and also had a more marked reduction in lung function than men.
To examine these differences, the researchers analyzed a couple of different subgroups of participants, all of whom suffered from COPD: one was the early-onset group (who were under 60 years old), and the other was the low exposure group (who had smoked for less than 20 years). In both groups, the team found that women suffered from a more severe form of the disease and also had a more marked reduction in lung function than men.
Soerheim isn't sure of the underlying mechanism behind the gender differences, but suggests that "[w]omen have smaller airways; therefore each cigarette may do more harm. Also, there are gender differences in the metabolism of cigarette smoke. Genes and hormones could also be important." Future research will need to delve into these possibilities in more detail.
Senior author Dawn DeMeo warns that "[m]any people believe that their own smoking is too limited to be harmful — that a few cigarettes a day represent a minimal risk. However, in the low exposure group in this study, half of the women actually had severe COPD. Clearly, there is no such thing as a safe exposure to cigarette smoke. Our findings suggest that this is particularly true for female smokers."