Table 2 Studies reporting risk of developing serious rsv (clinical diagnosis of rsv illness; N = 8)

Cohort study in premature infants

Gavin 2007 US [27]

Retrospective cohort study of 2098 premature infants (GA 32–35 weeks) in the Texas Medicaid program

Maternal smoking status during pregnancy from the birth certificate

Insurance claims for bronchiolitis or RSV hospitalization in the first year of life

NS, aOR, 0.78 (95% CI, 0.38–1.61)

Clinical diagnosis of RSV leading to misclassification could underestimate ETS exposure risk

Cohort studies in the general population

Boyce 2000 US [4]

Retrospective cohort study of children aged <3 years in the Tennessee Medicaid program from 1989–1993, with 248 652 child-years of follow-up

Maternal smoking status during pregnancy from the birth certificate

Insurance claims for bronchiolitis or RSV hospitalization in the first year of life

aRR, 1.3 (95% CI, 1.2–1.4)

Clinical diagnosis of RSV leading to misclassification could underestimate ETS exposure risk

Carroll 2007 US [28]

Retrospective cohort study of 101 245 term infants enrolled in the Tennessee Medicaid program

Maternal smoking status during pregnancy from the birth certificate

Insurance claims for bronchiolitis or RSV pneumonia in the first year of life

▪Hospitalization aOR, 1.28 (95% CI, 1.20–1.36)

Clinical diagnosis of RSV leading to misclassification could underestimate ETS exposure risk

▪ED visit aOR, 1.22 (95% CI, 1.13–1.31)

▪Clinic visit aOR, 1.06 (95% CI, 1.01–1.12)

▪Bronchiolitis diagnosis aHR, 1.14 (95% CI, 1.10–1.18)

Koehoorn 2008 Canada [29]

Retrospective cohort study of 93 058 infants aged 2–12 months

Maternal smoking status during pregnancy from perinatal database

Diagnostic codes for bronchiolitis for outpatient visits or hospitalizations

▪Inpatient onlyaHR, 1.47 (95% CI, 1.27–1.69)

Clinical diagnosis of bronchiolitis leading to misclassification could underestimate ETS exposure risk

▪Outpatient or inpatient NS in multivariate model, aHR, 1.03 (95% CI, 0.97–1.09)

Maternal smoking during pregnancy was significant in bivariate analysis for both case definitions, but when included in the multivariate models, it was significantly associated only with the inpatient (more severe) case definition

▪Significant in bivariate analysis, OR 1.14 (95% CI, 1.08–1.21); no P value reported

Marbury 1996 US [30]

Prospective cohort study of 1424 children with private insurance followed to age 2 years

Maternal smoking status

Diagnosis of bronchiolitis from electronic medical records

NS, aRR, 1.3 (95% CI, 0.8–2.2); no P value reported

Clinical diagnosis of bronchiolitis leading to misclassification could underestimate ETS exposure risk The authors noted that smokers were less likely to participate in the study (the Indoor Air and Children’s Health Study) and that smokers who participate may differ from those who do not. They also noted the possibility of underreporting of smoking

Reese et al., 1992 Australia [18]

Retrospective cohort study of 491 patients up to age 17 years admitted to an Australian children’s hospital June-Dec. 1987 for whom urinary cotinine levels were available.

Urinary cotinine level, analyzed without knowledge of exposure status or diagnosis

Hospitalization with diagnosis of bronchiolitis vs. a non-respiratory diagnosis (limited to patients aged 5–15 mos in the nonrespiratory illness group)

Elevated cotinine levels found in bronchiolitis vs. nonrespiratory illness group (P < 0.02) Subanalysis of the bronchiolitis group by RSV status found no significant difference between RSV-positive (n = 16) and RSV-negative (n = 23) patients; both subgroups had elevated cotinine vs. the nonrespiratory illness group

Risk of confounding not clear; regression analysis appears to have been performed but was insufficiently reported (no aORs reported)

Among those with cotinine levels, 41 patients (aged 5–15 mos.) were diagnosed with bronchiolitis

Case–control studies in the general population

Holman 2003 US [3]

Case–control study of 224 infants aged <1 year who died from bronchiolitis, and 2336 controls

Maternal smoking status during pregnancy

Bronchiolitis death from death certificate data

aOR, 1.6(95% CI, 1.0–2.6)

Clinical diagnosis of bronchiolitis from death certificate leading to misclassification could underestimate ETS exposure risk

McConnochie 1986 US [31]

Case–control study of 53 cases of bronchiolitis and 106 controls in children aged <2 years presenting to a physician’s officeBivariate analysis included 3 ETS exposure variables, but only “passive smoking” was included in the multivariate analysis

Any passive smoking

Bronchiolitis from diagnostic registry and record review

aOR, 3.87 if no family history of asthma (no CI or P value reported)aOR, 4.03 if family history of asthma (no CI or P value reported)

Clinical diagnosis of bronchiolitis leading to misclassification could underestimate ETS exposure risk Interviews related to smoking status were conducted approximately 7.8 years after the bronchiolitis episodes; current and former smokers at the time of the interview were assumed to be smoking at the time of the bronchiolitis episode

Smoking in household

Bronchiolitis

Bivariate OR, 3.21 (95% CI, 1.42–7.25)

Mother smokes

Bronchiolitis

Bivariate OR, 2.33 (95% CI, 1.19–4.57)

Father smokes

Bronchiolitis

NS in bivariate model, OR 1.71 (95% CI, 0.87–3.33)