Table 5.5

Studies of secondhand smoke exposure and sudden infant death syndrome (SIDS)

StudyDesign/populationExposure categoriesSource of exposureOutcomeFindingsComments
Bergman and Wiesner 1976 Case-control (56 cases, 86 controls, matched for gender, race [all Caucasian], and date of birth)
United States (King county, Washington state)
1970–1974
  • Mother smoked after pregnancy
  • Father smoked
  • Mother and father
SIDSMaternal smoking
 OR* = 2.42 (95% CI, 1.22–4.82)
Paternal smoking
 OR = 1.53 (95% CI, 0.78–3.01)
Unadjusted
Exposure data were self-reported (mailed questionnaire); all cases were autopsied; OR and CI were calculated from prevalence estimates provided in the paper; exposure to secondhand smoke appears to enhance the risk of SIDS; potential confounders were not assessed
McGlashan 1989 Case-control (167 cases, 334 controls, matched for gender, born in same hospital, and proximate date of birth)
Australia (Tasmania)
1980–1986
  • Smoking status of parents
  • Cigarettes/day smoked by mother (habitual, during pregnancy, and during the infant’s first year)
  • Mother and father
SIDSFather was habitual smoker
 RR = 1.73 (p = 0.05)
Mother smoked during infant’s first year
 RR = 2.20 (p <0.01)
During infant’s first year, mother smoked
 >10 cigarettes/day: RR = 2.37 (p <0.05)
 >20 cigarettes/day: RR = 3.11 (p <0.05)
Exposure data were self-reported (interview); all cases were autopsied; RR was based on statistical analysis of case-2 matched control “triples”; dose-response for level of paternal smoking was noted but RR was not reported; parental smoking carries a high relative risk for SIDS
Mitchell et al. 1991 Case-control (128 cases, 503 controls randomly selected from all births)
New Zealand
1987–1988
  • Cigarettes/day smoked by mother during the 2 weeks before the interview
  • Mother
SIDSIn the past 2 weeks, mother smoked
 1–9 cigarettes/day: OR = 1.87 (95% CI, 0.98–3.54)
 10–19 cigarettes/day: OR = 2.64 (95% CI, 1.47–4.74)
 ≥20 cigarettes/day: OR = 5.06 (95% CI, 2.86–8.95)
Unadjusted
Exposure data were self-reported (interview); all cases were autopsied; maternal smoking is an independent risk factor for SIDS
Nicholl and O’Cathain 1992 Case-control (303 cases, 277 controls, matched for date and place of birth)
United Kingdom
1976–1979
  • Prenatal and postnatal smoking status of the mother’s partner
  • Mother’s partner
SIDSNeither mother nor her partner smoked during pregnancy
 1.0 (reference)
Mother did not smoke during pregnancy, partner did smoke prenatally and postnatally
 RR = 1.63 (95% CI, 1.11–2.40)
Exposure data were self-reported (interview); all cases were autopsied; adjusted for birth weight, maternal age and gravidity, and condition of the family’s housing; RR for paternal smoking increased over 4 age-at-death intervals; postnatal secondhand smoke exposure from the father plays a role in the risk of SIDS
Schoendorf and Kiely 1992 Case-control (435 cases ≥2,500 grams [g], 6,098 controls ≥2,500 g)
All infant deaths were from causes other than SIDS Sample was stratified by race:
 Black infants (103 cases, 2,423 controls)
 White infants (89 cases, 1,987 controls)
Data from the National Maternal and Infant Health Survey
United States
1988
  • None (no prenatal or postnatal maternal smoking), mother smoked after pregnancy (secondhand), and mother smoked during and after pregnancy (combined)
  • Secondhand smoke exposure from other household members (none vs. any)
  • Mother (smoked prenatally and postpartum)
  • Other household members (smoking status at time of survey)
SIDSFrom mothers
Black infants
 Secondhand: OR = 2.33 (95% CI, 1.48–3.67)
 Combined: OR = 3.06 (95% CI, 2.19–4.29)
White infants
 Secondhand: OR = 1.75 (95% CI, 1.04–2.95)
 Combined: OR = 3.10 (95% CI, 2.27–4.24)
Adjusted for marital status and maternal age and education

From other household members (none vs. any)
Black infants (by mother’s smoking category)
 None: OR = 1.00 (95% CI, 0.62–1.58)
 Secondhand: OR = 1.03 (95% CI, 0.43–2.47)
 All infants: OR = 0.93 (95% CI, 0.68–1.27)
White infants
 None: OR = 1.33 (95% CI, 0.77–2.27)
 Secondhand: OR = 1.63 (95% CI, 0.58–4.74)
 All infants: OR = 1.41 (95% CI, 1.04–1.90)
 Adjusted for marital status and maternal age and education
Race of infant defined as Black non-Hispanic and White non-Hispanic; control variables were selected from birth certificates; survey questionnaire was completed by the mother; possible bias in self-reported smoking behaviors of case and control mothers; 92% of cases were autopsied; both intrauterine and secondhand smoke exposures are associated with an increased risk of SIDS
Mitchell et al. 1993 Case-control (485 cases, 1,800 controls randomly selected from all births)
Data from the New Zealand Cot Death Study
1987–1990
  • Mother smoked during pregnancy
  • Father smoked during the past 2 weeks
  • Other household members smoked during the past 2 weeks
  • Cigarettes/day smoked by mother during the past 2 weeks, stratified by father’s smoking status
Smoking in the past 2 weeks by
  • Mother
  • Father
  • Other household members
SIDSMaternal smoking
 OR = 1.65 (95% CI, 1.20–2.28)
Paternal smoking
 OR = 1.37 (95% CI, 1.02–1.84)
Smoking by other household members
 OR = 1.17 (95% CI, 0.84–1.63)
Adjusted for region, time of day, infant’s age, maternal marital status, infant’s gender, socioeconomic status, birth weight, infant’s race, season, maternal age, sleeping position, bed sharing, breastfeeding, and maternal smoking during pregnancy; also adjusted for either maternal smoking during pregnancy, paternal smoking in the 2 weeks before the interview, or smoking by other household members in the past 2 weeks

Father did not smoke
In the past 2 weeks, mother smoked
 0 cigarettes: 1.0 (reference)
 1–19 cigarettes/day: OR = 2.56 (95% CI, 1.73–3.75)
 ≥20 cigarettes/day: OR = 3.43 (95% CI, 2.04–5.77)

Father smoked
In the past 2 weeks, mother smoked
 0 cigarettes: OR = 1.0 (95% CI, 0.64–1.56)
 1–19 cigarettes/day: OR = 4.40 (95% CI, 3.26–5.95)
 ≥20 cigarettes/day: OR = 7.40 (95% CI, 4.92–11.13)
Unadjusted
Extended the Mitchell et al. 1991 study using similar methods; exposure data were from obstetric records and self-reports (interview); autopsies were carried out in 474/485 (97.7%) of SIDS cases; infants of smoking mothers who were breastfed had a lower risk than infants of mothers who were not; secondhand smoke exposure is causally related to SIDS
Klonoff-Cohen et al. 1995 Case-control (200 cases, 200 controls)
United States (southern California)
1989–1992
  • Postpartum secondhand smoking status of household members was assessed using multiple methods including any smoking, quantity smoked, smoking in same rooom as the infant, number of hours spent smoking around the infant
  • Mother
  • Father
  • Other adult live-in residents
  • Day care providers
SIDSMaternal smoking
 Any: OR = 2.28 (95% CI, 1.04–4.98)
 In same room as infant: OR = 4.62 (95% CI, 1.82–11.77)
Paternal smoking
 Any: OR = 3.46 (95% CI, 1.91–6.28)
 In same room as infant: OR = 8.49 (95% CI, 3.33–21.63)
Smoking by other live-in adults
 Any: OR = 2.18 (95% CI, 1.09–4.38)
 In same room as infant: OR = 4.99 (95% CI, 1.69–14.75)
All combined household smoking
 Any: OR = 3.50 (95% CI, 1.81–6.75)
 In same room as infant: OR = 4.99 (95% CI, 2.35–10.99)

Exposure to cigarettes from all sources (mother, father, live-in adults, and day care providers
Total number of household smokers
 One: OR = 3.00 (95% CI, 1.51–5.97)
 Two: OR = 5.31 (95% CI, 1.94–14.54)
 Three–four: OR = 5.13 (95% CI, 0.72–36.61)
Number smoking in same room as infant
 One: OR = 3.67 (95% CI, 1.66–8.13)
 Two–four: OR = 20.91 (95% CI, 4.02–108.7)
Total daily cigarette exposure
 1–10: OR = 2.40 (95% CI, 1.06–5.44)
 11–20: OR = 3.62 (95% CI, 1.50–8.75)
 ≥ 20: OR = 22.67 (95% CI, 4.80–107.2)
Exposure data were self-reported (interview); all reported ORs were adjusted for birth weight (in grams), routine sleep position, medical conditions at birth, prenatal care, breastfeeding, and maternal smoking during pregnancy; breastfeeding was protective in nonsmokers but not in smokers; secondhand smoke exposure in the same room as an infant increases the risk for SIDS; risk of SIDS associated with secondhand smoke exposure was similar among different racial groups
Ponsonby et al. 1995 Case-control (58 cases, 62 age- and region-matched controls, 58 age-, region-, and birth weight-matched controls)
Australia (Tasmania)
1988–1991
  • Postpartum smoking status of mother
  • Mother
SIDSMother smoked postnatally (full multivariate model)
 OR = 2.39 (95% CI, 1.01–6.00)
Mother smoked postnatally (multivariate model excluding family history of asthma)
 OR = 3.10 (95% CI, 1.36–7.09)
Exposure data were self-reported (questionnaire); all cases were autopsied; adjusted for maternal age, usual sleeping position, employment status, and family history of asthma; postpartum maternal smoking is a predictor of SIDS
Blair et al. 1996 Case-control (195 cases, 780 controls, 4 per case matched for age)
United Kingdom (Southwest, Yorkshire, and Trent)
1993–1995
  • Smoking status of mother, father, and others in household
  • Number of smokers in household
  • Number of cigarettes smoked daily in household
Postpartum exposure from
  • Mother
  • Father
  • Other household members
SIDSParental smoking status
Only father smoked: OR = 3.41 (95% CI, 1.98–5.88)
Only mother smoked: OR = 7.01 (95% CI, 3.91–12.56)
Both parents smoked: OR = 8.41 (95% CI, 5.08–13.92)
Adjusted for maternal smoking during pregnancy

Multivariate analysis
Postnatal paternal smoking, additive to maternal smoking
 OR = 2.50 (95% CI, 1.48–4.22)
Adjusted for mother’s age, mothers without partners, parity, multiple births, short gestation, socioeconomic status, sleeping position, maternal alcohol consumption, parental use of illegal drugs, parental bed sharing, breastfeeding, and birth weight

Postnatal paternal smoking, additional adjustment for maternal smoking during pregnancy
 Nonsignificant (p = 0.1601)

Number of smokers at home
1 smoker: OR = 2.44 (95% CI, 1.36–4.37)
2 smokers: OR = 5.15 (95% CI, 3.24–8.21)
>2 smokers: OR = 10.43 (95% CI, 3.34–32.54)

Cigarettes/day smoked at home
1–19 cigarettes/day: OR = 2.47 (95% CI, 1.29–4.73)
20–39 cigarettes/day: OR = 3.96 (95% CI, 2.40–6.55)
>39 cigarettes/day: OR = 7.57 (95% CI, 4.00–14.32)

Infant’s daily exposure to tobacco smoke (hours)
1–2: OR = 1.99 (95% CI, 1.14–3.46)
3–5: OR = 3.84 (95% CI, 1.97–7.48)
6–8: OR = 6.78 (95% CI, 3.17–14.49)
>8: OR = 8.29 (95% CI, 4.28–16.05)
Exposure data were self-reported (questionnaire); multivariate analysis found nonsignificant effect for other smoking members of household; unclear if postnatal dose-response analyses adjusted for maternal prenatal smoking or other confounding factors; dose-response analyses were limited to households where smoking was allowed in the same room as the infant; exposure to secondhand smoke in the home has an independent effect on the risk of SIDS
Anderson and Cook 1997 Meta-analysis
Systematic qualitative review of epidemiologic evidence (studies were identified by electronically searching EMBASE§ and Medline)
39 relevant studies were assessed (43 papers)
  • Maternal prenatal and postnatal smoking
  • Mother
SIDSPrenatal maternal smoking
 OR = 2.08 (95% CI, 1.96–2.21)
 Postnatal maternal smoking
 OR = 1.94 (95% CI, 1.55–2.43)
Pooled adjusted ORs were calculated using a fixed effects model; calculated results are also available using a random effects model; results are also available for pooled unadjusted ORs; the relationship between maternal smoking and SIDS is almost certainly causal—maternal smoking doubled the risk
Brooke et al. 1997 Case-control (147 cases, 276 controls, 2 controls per case from births immediately before and after index case, thus matched for age, season, and maternity unit)
Scotland
1992–1995
  • Smoking status of mother and father
  • Mother and father
SIDSOnly father smoked
 OR = 2.12 (95% CI, 0.99–4.55)
Only mother smoked
 OR = 5.05 (95% CI, 1.85–13.77)
Both parents smoked
 OR = 5.19 (95% CI, 2.26–11.91)
Exposure data were self-reported (questionnaire); all cases were autopsied; adjusted for sleeping position, old mattress, maternal age, deprivation score, moved under sheets, maternal marital status, social class, use of cot bumper, sleeping with parents, symptoms in previous week, gestational age, was usually swaddled in previous week, history of infant death in family, sweaty upon waking, warmth, maternal education, beastfeeding, parity, and birth weight; parental smoking is confirmed as a modifiable risk factor for SIDS
Mitchell et al. 1997 Case-control (232 cases, 1,200 population controls)
New Zealand
1991–1993
  • Maternal cigarettes/day and paternal smoking status when infant was 2 months old
  • Mother and father
SIDSMaternal smoking (at 2 months home visit)
0 cigarettes/day: 1.0 (reference)
1–19 cigarettes/day: OR = 4.90 (95% CI, 2.65–9.06)
≥ 20 cigarettes/day: OR = 21.42 (95% CI, 6.89–66.52)

Paternal smoking (at 2 months home visit)
No: 1.0 (reference)
Yes: OR = 3.21 (95% CI, 1.81–5.71)

Risks from maternal/paternal smoking combinations
Nonsmoking mother
 Smoking father: OR = 1.54 (95% CI, 0.67–3.45)
Smoking mother:
 Nonsmoking father: OR = 4.15 (95% CI, 2.05–8.38)
 Smoking father: OR = 10.09 (95% CI, 5.89–17.37)

Adjusted OR (maternal smoking and bed sharing
Nonsmoking/no bed sharing: 1.0 (reference)
Nonsmoking/bed sharing: OR = 1.03 (95% CI, 0.21–5.06)
Smoking/no bed sharing: OR = 1.43 (95% CI, 0.58–3.51)
Smoking/bed sharing: OR = 5.02 (95% CI, 1.05–24.05)

Adjusted for maternal age, marital status, age mother left school, number of previous pregnancies, infant’s gender, ethnicity of infant, birth weight, sleep position, breasfeeding, and the combination of bed sharing and maternal smoking
Exposure data were self-reported (interviews conducted at postpartum and at 2 months postpartum); maternal smoking and bed sharing increase risk; maternal smoking is a significant risk factor for SIDS
Alm et al. 1998 Case-control (244 cases, 869 controls, matched for gender, date of birth, and hospital)
Denmark, Norway, and Sweden
1992–1995
  • Postnatal household secondhand smoke exposure
  • Mother
  • Father
  • Other household members
SIDSMaternal postnatal smoking
 OR = 3.7 (95% CI, 2.5–5.5)
Paternal postnatal smoking
 OR = 1.2 (95% CI, 0.8–1.9)
Smoking by other household members (after pregnancy)
 OR = 1.2 (95% CI, 0.6–2.2)
Exposure data were self-reported (questionnaire); all cases were autopsied; adjusted for age, maternal age, and maternal education; exposure to secondhand smoke is an independent risk factor for SIDS
Dwyer et al. 1999 Nested case-control study with prospective cohort study (35 cases, 9,765 controls); urinary samples for cotinine analysis were collected from 105 infants (August October 1995)
Australia (Tasmania)
1988–1995
  • Postnatal household secondhand smoke exposure
  • Mother
  • Other household members
SIDSPostnatal smoking
Maternal postnatal smoking (breastfed infants)
 OR = 5.29 (95% CI, 1.16–24.11)
Maternal postnatal smoking (bottle-fed infants)
 OR = 2.35 (95% CI, 0.73–7.62)
Smoking by other household members
 OR = 0.69 (95% CI, 0.34–1.40)

Dose-response of maternal postnatal smoking
None (no maternal postnatal smoking): OR = 1.0
1–10 cigarettes/day: OR = 2.80 (95% CI, 1.08–7.27)
11–20 cigarettes/day: OR = 3.01 (95% CI, 1.22–7.42)
21 cigarettes/day: OR = 5.31 (95% CI, 2.04–13.81)
Exposure data are from self-reports (interview) and from urinary cotinine measures (results from n = 100); all cases were autopsied; adjusted for breastfeeding, birth weight, and smoking in same room as infant; analyses of postnatal smoking among 34 cases and 9,464 controls; cotinine data provide estimates of exposure levels by self-reported categories; there is a positive association between maternal smoking and SIDS, but cannot separate risks from prenatal and postnatal smoking
*

OR = Odds ratio.

CI = Confidence interval.

RR = Relative risk.

§

EMBASE = Excerpta Medica Database.

OR = Odds ratio.

CI = Confidence interval.

RR = Relative risk.

EMBASE = Excerpta Medica Database.

From: 5, Reproductive and Developmental Effects from Exposure to Secondhand Smoke

Cover of The Health Consequences of Involuntary Exposure to Tobacco Smoke
The Health Consequences of Involuntary Exposure to Tobacco Smoke: A Report of the Surgeon General.
Office on Smoking and Health (US).

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