Table 6

Summary of principal design features and findings from cohort studies of effect of ETS exposure on lung function development

Study	Inclusion criteria	No of subjects with longitudinal data	Age at first measurement of lung function	Follow up	Assessment of exposure	Findings
Six Cities 70		All first and second grade school children in 6 US cities. Analyses restricted to non-smoking white children		8706		6–9	Subsequently up to 12 annual assessments	Detailed parental smoking data were collected annually as well as prior smoking. Analyses focused on exposure in first 5 years of life, cumulative exposure between age 6 and testing and current exposure.	Current maternal smoking was associated with slower growth rates in children 6–10 year of age for:
									FVC -2.8 ml/yr (−5.5 to 0.0)
									FEV₁ -3.8 ml/yr (−6.4 to −1.1)
									FEF₂₅₋₇₅ –14.3 ml/s/yr (−29.0 to 0.3)
									In older children the only significant effect was:
									FEF₂₅₋₇₅ –7.9 ml/s/yr (−14.4 to −1.4)
									Neither paternal smoking nor maternal smoking during the first 5 years of life were related to lung growth.
East Boston85		A 34% random sample of children 5–9 years at school in East Boston in 1974–5. These index children + their sibs formed the cohort.		852 children at initial examination of whom 633 were still followed at examination 6		6–19	Children were subsequently examined at yearly intervals on up to 5 occasions	Questionnaire assessment of maternal smoking at each examination as well as smoking prior to initial examination.	Current maternal smoking was associated with slower growth in: FEV₁ -27.88ml/yr (−5.5 to 50.1). This is equivalent to a 7% deficit over 5 years.
East Boston85						6–19			Similar effects were seen if the child smoked on top of the effect of active smoking. No effects of paternal smoking were observed.
Tucson 71 86	Multistage stratified cluster sample of white non-Mexican Americans in Tucson area	Children aged 4–19 from 344 households	4–19	Data from 1st 10 surveys	Questionnaire based assessment of maternal smoking at each survey.	No effect was observed on growth overall. A re-analysis has suggested that boys with low initial lung function may have reduced growth if passively exposed87. However, no interaction tests were performed to demonstrate that the effect of passive smoking was significantly different from that in high initial lung function boys or in girls.
Dutch 58		Children attending 10 schools in a rural area in south-east Netherlands. 832 (84%) of children participated		331		6–10	Pulmonary function subsequently measured 3 times over 2 years	Questionnaire based—smoking daily inside home v not	Cross sectional effects were seen based on larger numbers of subjects (cf Tables 2 and 4).
									Lung growth (adjusted for height and weight change, mean age, parental education and URTI at testing) was not significantly related to ETS.
									Regression coeffs for FEV₁ were:
									in girls +7 (6) ml/yr
									in boys −12 (7) ml/yr
Dunedin Cohort42		Birth cohort initially seen at age 3 years		634 original cohort at age 3 was 1139		9	Spirometry subsequently measured at ages 11, 13 and 15	Maternal and paternal smoking was assessed at ages 7, 9 and 11. Non-exposed children were those whose parents did not smoke in previous year at any of these examinations. Smoking habit of mother during pregnancy was obtained retrospectively at age 9 years.	The FEV₁/VC was lower in children whose parents both smoked (but significant only in boys) and declined faster with age in those with wheeze (significant for both sexes). Complicated modelling make interpretation of data difficult.
									Very selected presentation of FEV₁ and VC were made, with suggestions of effects in some subgroups.
									No significant changes in any pulmonary function measure were found in subjects where mothers reported smoking during and/or after pregnancy.
Arizona 30	Children attending schools in 3 small communities in Arizona.	472 subjects with a minimum of 2 consecutive annual tests	8–10	Up to 3 annual follow up tests	Neither parent v one parent v both parents, smoke	FEV₁ growth standardised for height was lower if both parents smoked compared to neither smoking in 3 out of 4 age groups. No overall estimate of effect, standard errors or p value is available.