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THE IMPACT OF A STEPWISE INTRODUCTION OF SMOKE‐FREE LEGISLATION ON THE RATE OF PRETERM BIRTHSCox B, Martens E, Nemery B, Vangronsveld J, Tim Nawrot
Centre for Environmental Sciences, Hasselt UniversityStudy Centre for perinatal epidemiologyCentre for Environmental Health, Leuven University
Invoeren van wetten rond rookstop en veranderingen in het populatierisico op vroeggeboorte
Pentalfa, 27 februari ‘14
Crystal E, et. al. Circulation 2012
TRIGGERS OF PRETERM BIRTH
Crump C et al. JAMA 2011
AIM
In Belgium, smoke‐free legislation was implemented in different phases. On 1 January 2006, public places and most workplaces became smoke‐free (phase 1). A ban on smoking in restaurants was introduced on 1 January 2007 (phase 2), while for bars serving food, smoke‐free legislation came into force on 1 January 2010
(phase 3).
We investigated whether these three smoking bans influenced the incidence in preterm deliveries in the population.
RATE OF PRETERM BIRTHS AND SMOKE FREE LEGISLATION
n=606 877
Cox B, et. al. BMJ 2013
Data perinatal epidemiology, all single births 2002-2012
METHODS
The immediate effect of smoke‐free legislation was modelled as a step function (step change), while the gradual effects were studied with an interaction term between the indicator variable and time (trend or slope change).
The models allowed for an underlying trend throughout the study period and were adjusted for infant sex, maternal age, parity, socio‐economic status [municipality level / individual level (in sensitivity analysis)], national origin, level of urbanization of maternal residence, month of the year, day of the week, public holidays, apparent temperature, and PM10. Both for apparent temperature and for PM10 we calculated the average exposure on the day of delivery and the day before, and we allowed for non‐linear associations with preterm birth by using natural cubic splines.
Cox B, et. al. BMJ 2013
METHODSinc
idence
time
intervention
slope change(events per year)
step change(events)
modelled incidenceintervention no effectstep change only
PRETERM BIRTH AND STEPWISE INTRODUCTION OF SMOKING BAN
ModelLegislation 2006 Legislation 2007 Legislation 2010
Step change Slope change Step change Slope change Step change Slope change
Spontaneous preterm delivery
2006 ‐3.24% ‐1.85%
n/a n/a n/a n/a(‐4.40; ‐2.07)** (‐2.42; ‐1.28)**
2007 n/a n/a‐3.69% ‐2.16%
n/a n/a(‐4.81; ‐2.55)** (‐2.85; ‐1.46)**
2010 n/a n/a n/a n/a‐3.36% ‐5.17%
(‐4.73; ‐1.98)** (‐7.36; ‐2.94)**
Final ‐ ‐‐3.13%
‐ ‐‐2.65%
(‐4.37; ‐1.87)** (‐5.11; ‐0.13)**
Adjusted for underlying trend, newborn sex, maternal age, parity, socio‐economic status, urbanization, month of the year, day of the week, public holidays, and short‐term changes in apparent temperature and particulate air pollution (PM10).
To put the relative changes in perspective, these changes correspond to a reduction of 6 preterm births per 1000 deliveries over the 5 study years (after 2007).
n=606 877
Cox B, et. al. BMJ 2013
SENSITIVITY ANALYSIS
Atosiban is an inhibitor of oxytocin and vasopressin and is specifically used to halt premature labour.
Cervical cerclage is used for the treatment of cervical incompetence.
no substantial changes in the use of either treatment during the study period: the number of women given Atosiban varied from 59 per 1000 deliveries (846 prescriptions per
1000 deliveries) in 2005 to 63 per 1000 deliveries (753 prescriptions per 1000 deliveries) in 2011, and the number of cervical cerclages varied from 11 per 1000 deliveries in 2002 to 8 per 1000
deliveries in 2011.
‐11.0 % (95% CI: −17.2 to −5.1)p = 0.001
Mackay DF, et. al. PlosMed. 2012
SMOKING AND ACCPETANCE IN THE POPULATION
Akhtar, et. al. Tob Control. 2009 / Martin J Jarvis et al. Tob Control 2011
ENVIRONAGE BIRTH COHORT
MATERNAL SMOKING, MITOCHONDRIA AND EPIGENETICS
Janssen et al. Environ Health Perspect 2012
Meyer Jet al. Toxicological Sciences 2013
OVERALL CONCLUSIONS
Smoking ban study shows:
Consistent patterns of reduced preterm deliveries with successive population interventions to restrict smoking.
This further supports the notion that smoking bans have public health benefits even from early life on.
Placental tissue as a molecular ‘footprint’ for in utero exposure: mtDNA content:
In placental tissue at birth a decreased mtDNA content is associatedwith maternal smoking.