smoking

Cigarette smoking is clearly the single most important risk
factor in the development of COPD. Current smoking is also
associated with an increased risk of death. Pipe and cigar
smoking also significantly increase morbidity and mortality
from COPD, though the risk is less than for cigarettes. Around
half of cigarette smokers develop some airflow obstruction, and
10-20% develop clinically significant COPD. Although smoking
is the most important risk factor, it is not a prerequisite: COPD
can occur in non-smokers with longstanding asthma or with

1 antitrypsin deficiency. Moreover, about 20% of COPD cases
in men are not attributable to smoking.
A more contentious issue is the possible relation between
environmental tobacco smoke and development of COPD:
several case-control studies have shown a trend towards an
increased risk of COPD with passive smoking. However, the
adverse effect of maternal smoking on childhood ventilatory
function is clearer: smoking during and after pregnancy is
associated with reduced infant, childhood, and adult ventilatory
function. Most studies have shown that the effects of antenatal
smoking are greater in magnitude than, and independent of,
the effects of postnatal exposure.