The determination of the effect of passive smoking on lower respiratory tract infections in children aged 2-12 years by urinary cotinine and eosinophil cationic protein levels

Aim. The aim of this community-based and case-control study was to determine the effect of passive smoking on lower respiratory tract infections in children by urinary cotinine and eosinophil cationic protein values. Methods. The minimum sample size of the study was determined as 148 children in case and control groups at 95% confidence interval, 80% power, case/control considered equal, odds ratio=2.0, and possible exposure prevalence 50%; 150 children with lower respiratory tract infection and 150 healthy children were included in the study. The children aged 2 to 12 years with lower respiratory tract diseases in the study carried out between October 2003 and March 2004 were selected from the records of three health centres in Narlidere district. The children in control groups were healthy children who were paired with the cases obtained from the same health centres according to age, gender and street of the residing area. The residences of children diagnosed with LRTI and, also healthy children were visited within first 3 days of diagnosis, and a specialy designed questionnaire was used to obtain information, and urine samples were collected. The urine cotinine and eosinophil cationic protein levels were measured by radioimmunoassay and fluoro enzyme immunoassay methods respectively. Data were analyzed on SPSS 11.0 programme, and were assessed by McNemar Chi-square, paired t-test and pearson corelation test. P< 0.05 was accepted statistically significant. Results. The prevalence of parental self-reported, indoor smoking was 71.3% in children with lower respiratory tract infection and 72.0% in healthy children. According to the value of urinary cotinine/creatinine for 30 ng/mg, the prevalence of passive smoking was 87.3% in case group and 84.7% in control group (p=0.618). When the cut-off level of urinary cotinin/creatinine was accepted as 60 ng/mg, it was found that passive smoking increased lower respiratory tract infection 4.7 times (p<0.001). The mean urine eosinophil cationic protein values were significantly higher in the case group compared with the healthy children group (p=0.018). A positive association was determined between urinary cotinine and eosinophil cationic protein values in children with lower respiratory tract infection (p=0.034). Conclusion. Dose-dependent exposure to environmental tobacco smoke increases the prevalence of lower respiratory tract infection in children. Lower respiratory tract infections together with passive smoking may be a risk factor for bronchial hyperresponsiveness by airway inflammation. Keywords. lower respiratory tract infection, eosinophil cationic protein cotinine, passive smoking