To the Editors:
Chronic obstructive pulmonary disease (COPD) is rapidly becoming a global public health crisis, with around three million people predicted to die from the disease in 2006 1, 2. There is growing awareness of the increasing global burden of COPD not only in terms of mortality, but also its prevalence, morbidity and economic costs 2. In response to these concerns, there has been a renewed research effort to understand the causes of COPD and to develop public health and pharmacological interventions that may reduce the burden.
Smoking is recognised as the most important causative factor for COPD, with an individual's susceptibility being a continuous, rather than a categorical characteristic that can interact synergistically with other risk factors. There is now evidence that most smokers develop some respiratory impairment due to COPD 3. One of the most informative recent studies addressing this …
