Table 1

Inclusion criteria based on PICOS strategy

PICOSInclusion criteriaExclusion criteria
  1. 0–16 years old

  2. (Sub)populations in which at least 50% is under 17 years of age

Adult population without a distinct child subgroup
InterventionSmoke-free policies instituted at any governmental or institutional level that restrict smoking in designated (semi)private places or/and any outdoor areasSmoke-free policies covering only enclosed public places
  1. A comparison population living in a location where no intervention was introduced/changed in the observational period

  2. A comparison time period in which no intervention was introduced/changed

OutcomesI. Child TSE:
Primary outcome:
  1. TSE in places covered by the policy (as reported by child and/or parent/primary caregiver)

Secondary outcomes:
  1. TSE in places of which only some were covered by the policy or in unspecified places (as reported by child/parent/primary caregiver)

  2. TSE in places not covered by the policy (as reported by child/parent/primary caregiver)

  3. Cotinine or other specific biomarkers of TSE quantified in body fluids, hair, nails or on the skin

  4. TSE assessed by wearable devices

II. Child health outcomes:
Primary outcomes:
  1. Unplanned hospital attendance for wheezing/asthma

  2. Unplanned hospital attendance for RTIs

Secondary outcomes:
  1. General incidence of wheezing/asthma

  2. General incidence of RTIs

  3. OME

  4. Chronic cough

  5. FEV1, FVC, FEV1/FVC ratio

  1. Child TSE outcomes that are not specific to tobacco smoke (eg, PM2.5 and CO)

  2. Outcomes that do not necessarily imply a change in child TSE (eg, changes in tobacco smoke constituent level in a room)

  3. Outcomes assessing smoking initiation/cessation or smoking behaviour (eg, among parents)

Study designIncluded in the main analyses:
  1. Randomised trials

  2. Non-randomised trials

  3. Interrupted time series

  4. Controlled before–after studies

Included in sensitivity analyses:
  1. Prospective cohort studies

  2. Retrospective cohort studies

  3. Uncontrolled before–after studies

  • Lung function represents FEV1, FVC, FEV1/FVC ratio.

  • CO, carbon monoxide; FEV1, forced expiratory volume in one second; FVC, forced vital capacity; OME, otitis media with effusion; PICOS, Population, Intervention, Comparison, Outcomes, and Study design; PM2.5, fine particulate matter; RTI, respiratory tract infection; TSE, tobacco smoke exposure.