Trends in passive smoking in cystic fibrosis, 1993-1998.

We set out to study trends in exposure to passive smoking in children with cystic fibrosis over a 5-year period. We also evaluated the effects of this exposure on lung function. Cross-sectional data were collected on 52 children in 1998 and compared with similar data collected on 56 children in 1993. Within these two groups, there were 34 children who were studied on both occasions. Data collected included: questionnaire information about family smoking habits; forced expiratory volume in 1 sec (FEV1); forced vital capacity (FVC); and measurements of urinary and salivary cotinine levels. Salivary cotinine was more closely related to family smoking behavior than urinary cotinine concentrations (r for salivary cotinine = 0.54, P < 0.001; r for urinary cotinine = 0.37, P = 0.008). In 1993, 26/56 (46%) households contained at least one smoker (smoking households) compared with 23/52 (44%) in 1998. In 1993, a median of 15 cigarettes was smoked/day in smoking households compared to 20 cigarettes/day in 1998. In the longitudinal group, there was a small, nonsignificant reduction in mean urinary cotinine levels (geometric mean, 1993 = 5.03 ng/mL; 1998 = 4.76 ng/mL; P = 0.4). There was no significant difference between the smoking and nonsmoking households in change in lung function over 5 years (fall in FEV1 in smoking households, 10.3% vs. 11.2% in nonsmoking households; P = 0.87). We conclude that in a group of children with cystic fibrosis followed over 5 years, there was little reduction in passive smoking exposure. We did not show a relationship between such exposure and decline in lung function. A larger study will be necessary to determine whether such an effect is present. .