Table 3

Strengths and limitations of selected studies

StudyStrengthLimitationConfounder adjustment
Kallio et al
Circa Cardiovasc Qual Outcomes. 201028
  1. ETS tested at multiple timepoints during 8–13 years

  2. Objective biomarkers

  3. The first research: indicates that frequent ETS exposure is related to thicker CIMT among healthy 13-year-old adolescents

  4. Interobserver variation reported

  5. Dose-response relationship investigated

  6. Measurements of other indexes such as FMD and apolipoprotein

  1. No information about the children’s exposure before the age of 8 years

  2. The possibility of having active adolescent smokers among the participants

  3. Retrospective ascertainment of smoking in pregnancy (questionnaire)

  4. Potential residual confounding by family SES, breastfeeding, pubertal status

Confounders used:
BMI, diastolic BP, sex, pubertal status, STRIP study grouping (intervention or control), ApoB, ApoA-I, LDL cholesterol, and FMD
Geerts et al
Pediatrics. 201227
  1. The first study investigates this relationship in younger age group

  2. Comprehensive collection on exposure variables including prenatal, perinatal and postnatal period

  3. Able to distinguish the effect caused by prenatal and postnatal exposure

  4. Dose–response relationship was investigated

  5. Cumulative exposure was measured (questionnaire, amount and duration)

  1. Self-reported exposure condition

  2. Slightly different demographic characteristics between the prenatal mother smoking group and non-smoking group

  3. Small sample of smoking mothers with limited statistical power

  4. Children’s CIMT mean value was not provided

Two adjusted models:
  1. Age, sex, maternal age at birth and breast feeding;

  2. Difference in BMI z-score (BMI z-score at 4 weeks after birth, and BMI z-score at the children’s age of 5 years)

Yang et al
J Renin-Angio-Aldo S.
201229
  1. Participants were randomly recruited from school

  2. Exposure was measured by serum cotinine level

  3. Lipid profile was tested

  4. Active adolescent smokers were excluded

  5. Even participants with low exposure level were shown to have thicker CIMT

  1. Male sex only

  2. No non-exposed control group

  3. Hypoxia (in Tibet) is the risk factor of AS

  4. One technician for the CIMT measurement

No adjustment was made
Ayer et al
European Heart Journal. 201124
  1. ETS was measured at multiple timepoints: 1 year, 5 years, 7.5 years, etc.

  2. The first research: indicates the independent role of prenatal ETS exposure on children’s risk of future CVD

  3. Detailed exposure condition was recorded in each trimester

  1. Exposure measured by questionnaire (might underestimate the exposure rate)

  2. Non fasting blood at 8 years.

  3. No further adjustment on ETS and CIMT

Since the mean CIMT was not significantly different among groups in univariate analysis thus this study did not go for multivariate adjustment
  • ApoA-I, apolipoprotein A; ApoB, apolipoprotein B; AS, atherosclerosis; BMI, body mass index; BP, blood pressure; CIMT, carotid intima–media thickness; CVD, cardiovascular disease; ETS, environmental tobacco smoke; FMD, fibromuscular dysplasia; LDL, low-density lipoprotein; SES, socioeconomic status; STRIP, Special Turku Coronary Risk Factor Intervention Project.