To evaluate the impact of parental smoking on childhood asthma and wheezing
, we studied two random samples of subjects ages 6-7 and 13-14 years in ten
areas of northern and central Italy. Standardized questionnaires were comp
leted by parents of 18,737 children and 21,068 adolescents (response rates,
92.8% and 96.3%, respectively) about their smoking habits and the respirat
ory health of their children. Adolescents were asked about their respirator
y health and personal smoking. We compared two groups of cases with healthy
subjects: (1) "current asthma" (children, 5.2%; adolescents, 6.2%) and (2)
"current wheezing" not labeled as asthma (children = 4.5%, adolescents = 8
.5%). Exposure to smoke of at least one parent increased the relative risk
of current asthma among children [odds ratio (OR) = 1.34; 95% confidence in
terval (CI) = 1.11-1.62] and of current wheezing among adolescents (OR = 1.
24; 95% CI = 1.07-1.44). Maternal smoking had a stronger effect than patern
al smoking. Maternal smoking during pregnancy was associated with current a
sthma (OR = 1.62; 95% CI = 1.34-1.96) and current wheezing in children (OR
= 1.31; 95% CI =:1.06-1.62);the effects were lower among adolescents. Among
subjects with a negative history of parental asthma, maternal smoking was
associated with current wheezing in both age groups, whereas among those wi
th a positive history of parental asthma it was associated with current ast
hma in children, but not in adolescents. We estimated that 15% (95% CI = 12
-19) of the current asthma cases among children and 11% (95% CI = 8.3-14) o
f the current wheezing cases among adolescents are attributable to parental
smoking in Italy.