Changes in child exposure to environmental tobacco smoke CHETS after implementation of smokefree leg

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• Changes in child exposure to environmental
  tobacco smoke (CHETS) after implementation of
  smoke-free legislation in Scotland
• Candace Currie1, Patricia Akhtar1, Dorothy
  Currie1 and Sally Haw21Child and Adolescent
  Health Research Unit (CAHRU)The University of
  Edinburgh
• 2NHS Health Scotland

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Background

• A primary aim of the legislation was to reduce
  exposure to secondhand smoke (SHS) in public
  places
• No previous studies had assessed the impact of
  smoke-free legislation on childrens exposure to
  secondhand smoke

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Background

• Substantial proportion of young people are
  exposed to secondhand smoke (SHS) in own home
• Legislation may increase such exposure through
  displacement of adult smoking from public places
  into home

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Study Aim

• To examine impact of smoke-free legislation on
  childrens exposure to SHS at a population level
• Including examination of evidence for increased
  parental smoking at home associated with
  implementation of Scottish smoke-free legislation

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Outcomes measured before and after legislation

• Objective
• Childrens salivary cotinine levels
• Subjective
• Childrens reported exposure to environmental
  tobacco smoke in public and private places

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Methods

• Repeat cross-sectional design
• 2 nationally representative class based surveys
  of children in final year of Primary school (aged
  11 years)
• Same schools 1 year apart (before/ after
  legislation)
• All mainstream primary schools in mainland
  Scotland in sample frame
• Data collection
• salivary cotinine
• self-report questionnaire

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Administration of survey saliva collection

• Administered by trained researchers in classroom
• Pupils completed anonymous confidential
  questionnaire with questions on
• own smoking status
• smoking status of parent figures lived with
• recent exposure in public and private locations
• Pupils asked to provide saliva sample

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Saliva collection method

• cotton wool dental roll (salivette)
• in mouth for at least 3 minutes
• supervising researchers non-smokers
• samples stored in smoke-free environment prior to
  analysis

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Cotinine

• Major metabolite of nicotine
• High specificity and sensitivity as biomarker for
  exposure to nicotine from SHS
• Has half life of 20 hours (longer than nicotine)

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Cotinine detection

• Salivary cotinine concentrations determined using
  capillary gas chromatography with a specific
  nitrogen/phosphorous detector from a 100µl sample
• Assay had detection limit of 0.1ng/ml

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Child reports definitions

• Parental smoking status
• smokes everyday or sometimes smokers
• Number of smoker parent figures each child lived
  with
• (based on family structure and parental smoking
  status)
• 0 (none)
• 1 (father only)
• 1 (mother only)
• 2 (both)

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Child reports definitions

• Socioeconomic status
• Measured using Family Affluence Scale (FAS)
• FAS score based on number family car(s),
  computer(s), holiday(s) and bedroom occupancy
• Sample split into thirds and categorised as being
  from Low, Medium or High affluence families

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Analysis issues

• Smokers
• Children who reported that they were smokers or
  who had cotinine concentrationgt15ng/ml (cut off
  for active smoking) were excluded (lt2)
• Design effects
• Clustering, due to classes of pupils being
  sampled, was accounted for in analysis design

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School and pupil response rates

• Schools taking part
• 2006 survey 116/170 (68)
• 2007 survey 111 of original 116 (65)
• Pupils taking part
• 2006 survey 86
• 2007 survey 85

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Sample Characteristics
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Pupil smoking status
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Family structure
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Study findings changes in pupils exposure to SHS

• OBJECTIVE MEASURE
• Change in population-level cotinine concentration
• SUBJECTIVE MEASURES
• Changes in self-reported exposure in private and
  public locations

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Distribution of cotinine concentration before
smoke-free legislation
COTININE
BELOW LOD
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Distribution of cotinine concentration before and
after smoke-free legislation
BELOW LOD
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Population change in secondhand smoke exposure
before and after legislation

• Mean cotinine concentration in population
  sampled decreased by 39
• in 2006 0.36 (CI 0.32 to 0.40)ng/ml
• in 2007 0.22 (CI 0.19 to 0.25)ng/ml

( Geometric mean adjusted for age and Family
Affluence)
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Pupils reported exposure to SHS in private
locations
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Pupils reported exposure to SHS in public
locations
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Differential change in SHS exposure

• Are there differences in the extent of change
  according to the number of parent figures in the
  home who smoke?
• Is the 39 change in cotinine concentration in
  population observed in all groups of pupils?

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Definitions

• Parental smoking status
• smokes everyday or sometimes smokers
• Number of smoker parent figures each child lived
  with (on basis of family structure and reported
  parental smoking status)
• 0 (none)
• 1 (father only)
• 1 (mother only)
• 2 (both)

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Proportion of pupils by number of parent figures
in home who smoke
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Geometric mean cotinine concentration (95 CI)
before and after legislation by number of smoking
parental figures
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Differential changes in exposure

• Within all groups there was a fall in geometric
  mean cotinine concentrations after legislation
• This drop only significant among groups with
  lower levels of exposure
• - no parent figures smoke (51 fall) and
• - only father figure smokes (44 fall)

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Differential changes in exposure

• Pupils living in household where mother figure
  only smokes or both parent figures smoke
  geometric mean cotinine concentrations fell by
  11 (not statistically significant)

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Summary of main findings

• Evidence of population level change in exposure
  to SHS among primary 7 children in Scotland after
  legislation
• Overall SHS exposure fell 39 between January
  2006 and January 2007
• Greatest reduction in pupils living in households
  with lower levels of exposure

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Summary of main findings

• Evidence of a reduction in SHS exposure in public
  locations including cafes/restaurants and
  buses/trains
• Among private locations, a fall in reported SHS
  exposure when visiting other peoples homes
  occurred after legislation.
• Little evidence of change between survey years in
  reported exposure in pupils own homes and cars

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Displacement

• No evidence that smoke-free legislation has led
  to displacement of adult smoking from public
  places into the home
• No increase in proportion of parent figures who
  smoke
• No increase in self-reported exposure in the home
• No increase in cotinine concentration among
  pupils living with parents who smoke

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Conclusions

• Smoke-free legislation has made rapid progress
  towards promoting health in children by reducing
  exposure to SHS
• 19 of children in our sample are still exposed
  to levels of SHS that, according to recent
  research, are harmful to arterial health (Kallio
  et al , 2007 in Circulation)
• Exposure to SHS in children is still an
  outstanding public health concern in Scotland

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Conclusions

• There is a need to
• Continue to raise awareness about health risks of
  passive smoking
• Communicate to adults that low levels of SHS pose
  substantial health risks to children
• Support adults to implement smoke-free rules in
  their homes and cars
• Promote smoking cessation among all adults,
  emphasising key health issues for those living
  with children