Bedsharing and maternal smoking in a population-based survey of new mothers: Analysis of the Oregon PRAMS Dataset Martin B. Lahr, M.D., M.P.H.* Kenneth D. Rosenberg, M.D., M.P.H. †‡ Jodi A. Lapidus, Ph.D. ‡ * Oregon Department of Human Services, Disability Determination Services † Oregon Department of Human Services, Office of Family Health ‡ Oregon Health & Science University, Dept. of Public Health and Preventive Medicine Eleventh Annual Maternal and Child Health Epidemiology Conference Miami, FL, December 9, 2005

BACKGROUND METHODS RESULTS DISCUSSION

SIDS Mortality and Prone Sleep Position Sources: Mortality data from the CDC, National Center for Health Statistics, National Vital Statistics System, at Prone sleep prevalence data from Task Force on Infant Sleep Position and Sudden Infant Death Syndrome, Pediatrics 2000;105: http:// AAP Recommendations “Back to Sleep” Campaign

PNN Infant Mortality per 100,000 Live Births SIDS Unknown Suffocation bed Suffocation other PNN IMR (right axis)

Racial disparities in SIDS mortality, Mortality data from the CDC, National Center for Health Statistics, National Vital Statistics System, at Year Rate per 1000 live born Ratio Black White Total Ratio of Black to white deaths

SIDS: public health burden SIDS remains the third leading cause of infant mortality and the number one cause of postneonatal infant mortality –Overall, 0.57 deaths per 1000 live born (2002) –22.7% of all postneonatal infant deaths (2002) The decline in SIDS mortality that followed the “Back to Sleep” campaign has plateaued Public health practitioners seek other modifiable risk factors for SIDS

Oregon PRAMS “Oregon PRAMS, the Pregnancy Risk Assessment Monitoring System, is a project of the DHS Office of Family Health with support from the national Centers for Disease Control and Prevention (CDC). PRAMS collects data on maternal attitudes and experiences prior to, during, and immediately after pregnancy for a sample of Oregon women.”

BACKGROUND METHODS RESULTS DISCUSSION

Oregon PRAMS Stratified, random within strata, over-sampling of first five strata 1.Hispanics 2.Non-Hispanic (NH) blacks 3.NH Asians & Pacific Islanders 4.NH American Indians & Alaskan Natives 5.NH whites with low birthweight babies 6.NH whites with normal birthweight babies Weighted 1) to Oregon’s population, 2) for non-response, and 3) for non-coverage

Oregon PRAMS Monthly sample from birth certificates Nov Oct surveys mailed 1867 surveys completed Mixed mode: 1 st mailing – 1308 responses 2 nd mailing Computer-assisted telephone interview – % strata-weighted response

PRAMS Response 1867 completed 53 excluded –babies were no longer alive and/or no longer living with mother 38 excluded –did not indicate whether or not their babies were alive and living with mother 1776 eligible for analysis. 32 did not answer bedsharing question 1758 (99% of those eligible) included in the analysis.

PRAMS Question 62. Maternal-infant bedsharing. “Always” and “almost always” responses combined as “frequent” bedsharing for logistic regression. “Sometimes” and “never” responses combined as “infrequent” bedsharing for logistic regression. Analysis performed using SUDAAN  Always  Almost always  Sometimes  Never 62. How often does your new baby sleep in the same bed with you? Check only one.

Potential confounders Race/ethnicity Maternal education Maternal age Parity Marital status Urban vs. mixed density vs. rural county of residence Initiation of prenatal care Adequacy of prenatal care WIC enrollment Birthing hospitals by size Insurance - at labor & delivery and current Family income Infant gender Infant birthweight Bed-sharing status Breastfeeding duration Smoker before, during or after pregnancy PRAMS mode of administration

BACKGROUND METHODS RESULTS DISCUSSION

Bedsharing prevalence among respondents

Smoking prevalence among respondents

Factors associated with postpartum smoking Black, white and Native American race Younger maternal age Less maternal education Single marital status Lower income Oregon Health Plan WIC enrollment Shorter duration of breastfeeding Rural or frontier residence

Prevalence of bedsharing by maternal prenatal smoking status 12.3% of the respondents reported smoking during the third trimester

Prevalence of bedsharing by maternal postpartum smoking status 17.1% of the respondents reported current smoking

frequent* Multivariable logistic regression: maternal smoking & frequent* bedsharing Crude OR (95% CI) Adjusted OR (95% CI) † Wald-F p value Prenatal smoking Yes No 1.03 (0.64 – 1.68) (0.50 – 1.64) Postpartum smoking Yes No 0.81 (0.54 – 1.23) (0.42 – 1.25) * frequent = always or almost always, as compared to infrequent (sometimes, never) † adjusted for race/ethnicity, mother’s age, education and marital status, income, breastfeeding status, WIC enrollment, health insurance and county of residence

BACKGROUND METHODS RESULTS DISCUSSION

New Zealand Cot Death Study Population-based case-control study 393 cases and 1592 controls Data collected Multiple publications based on same dataset, beginning in 1992 Confirmed that prone infant sleep position was a major modifiable risk factor for SIDS Looked for other modifiable risk factors

New Zealand Cot Death Study Initial publication 1992 reported that bedsharing was a risk factor for SIDS, OR 2.02 ( ) –Did not stratify subjects 1993 reported the association between bedsharing and SIDS was only seen among Maoris, not non- Maoris 1994 reported this association only among smoking mothers, not nonsmoking mothers –Interaction seen among both Maoris and non-Maoris –Association of bedsharing & SIDS among those of Maori race was due to higher prevalence of smoking (confounder) among Maoris

Published studies on SIDS & bedsharing Study Carpenter & Shaddick (England) New Zealand Cot Death Study Year Published Data Years Type of StudyCase-Control Cases/Controls110/196393/1592 Results Bedsharing: risk, p <.05 but “of doubtful validity”. Prone sleep NOT a risk! Nonsmoking mothers: no risk. Smoking mothers: OR 3.15 ( )

Published studies on SIDS & bedsharing Study Klonoff-Cohen, et. al. (California) CESDI-SUDI (England) Year Published Data Years Type of StudyCase-Control Cases/Controls200/200195/780 Results Bedsharing: no risk. No interaction with smoking. Nonsmoking mothers: no risk. Smoking mothers: OR 9.25 ( )

Published studies on SIDS & bedsharing Study New Zealand Case- Cohort Study CESDI-SUDI (England) Year Published Data Years Type of StudyCase-CohortCase-Control Cases/Controls127/922325/1300 Results Nonsmoking mothers: no risk. Smoking mothers: 5.02 ( ). Nonsmoking mothers: no risk. Smoking mothers: ( ).

Published studies on SIDS & bedsharing Study Brooke, et. al. (Scotland) Tappin, et. al. (Scotland) Year Published Data Years Type of StudyCase-Control Cases/Controls201/276131/278 Results Bedsharing: no risk Did not stratify by smoking status. Bedsharing risk 3.36 ( ). Didn’t stratify by smoking status. Report (2005) reanalyzed data.

StudyYear Published Data Years Type of Study Results USPSC Case Series 2178 “suffocation” deaths. Bedsharing is dangerous. USPSC Case Series 394 cases of entrapment, 121 cases of “overlay asphyxiation.” Bedsharing is dangerous. Kemp, et. al. (St. Louis County) Case Series 118 consecutive ME cases. 47% shared a sleep surface but only about half were in adult beds; smoking status not available. Arnestad, et. al. (SE Norway) Case Series 174 SIDS cases and “controls.” Increase in proportion SIDS victims found cosleeping between periods. Likely recall bias. Published studies on SIDS & bedsharing

Study Year Published Data Years Type of Study Results Carroll- Pankhurst, et. al. (Cleveland) Case Series 84 SIDS cases. Bedsharing cases were young than other cases (p =.048). Person, et. al. (Upstate New York) Case Series 56 cases. 48.2% bedsharing, but only 25% shared adult bed. Unger, et. al. (St. Louis County) Case Series 118 cases. Bedsharing was twice as common among black cases as nonblack; black infants were more likely to share a sofa or makeshift bed or to share with siblings. USPSC , Case Series 1396 “suffocation” deaths. Of these 299 “suffocated” in cribs and 543 in adult beds. Knight, et. al. (Kentucky) Case Series 697 consecutive cases. 36.2% of ME files mentioned cosleeping. Published studies on SIDS & bedsharing

Study Chicago Infant Mortality Study McGarvey, et. al. (Ireland) Year Published2003 Data Years Type of StudyCase-Control Cases/Controls260/260203/622 Results Bedsharing with parents: no risk. No interaction with smoking. ORs range from but no confidence intervals given. Report published 2005 added subjects.

Published studies on SIDS & bedsharing Study Matthews, et. al. (Ireland) ECAS (Europe) Year Published2004 Data Years (2 nd pub.) Type of StudyCase-Control Cases/Controls203/622745/2411 Results Sample size too small for stable estimates when both bedsharing and prone sleep added to the model. Article published 2005 added subjects. Nonsmokers if infants > 8 weeks of age: no risk. 2 weeks of age: 2.4 ( ) Smoking mothers: high risk at any infant age.

Published studies on SIDS & bedsharing Study Tappin, et. al. (Scotland)McGarvey, et. al. (Ireland) Year Published 2005 Data Years (reanalyzed) (expanded) Type of Study Case-Control Cases/Controls 123/263287/831 Results Nonsmokers if infants > 11 weeks of age: no risk. Nonsmokers and < 11 weeks, OR 8.01 ( ). Smoking mothers: risk higher at all ages. Bedsharing risk if ≤ 10 weeks old, OR 8.02 ( ) but not if older, adjusted for but not stratified by smoking. No risk among nonsmokers as a whole. Smoking & bedsharing interacted.

Published studies on SIDS & bedsharing Summary of studies –8 uncontrolled case series raising a question of risk –9 large case control studies 3 did not report results stratified by maternal smoking status but none found an association between bedsharing & SIDS (1,2,3) 6 provided stratified results –3 found no association between SIDS and bedsharing among nonsmoking mothers; among smoking mothers, risk was increased (4,5,6) –1 found an increased risk for infants 11 weeks old; and an increased risk for smoking mothers but not nonsmokers (7) –2 found no association between SIDS and bedsharing among nonsmoking mothers of infants > 11 weeks old but did find a risk for infants < 8-11 weeks old and for all infants of smoking mothers (8,9)

Revised AAP recommendations – October 2005 * “Bed sharing is not recommended during sleep. Infants may be brought into bed for nursing or comforting, but should be returned to their own crib or bassinet when the parent is ready to return to sleep. However, there is growing evidence that room sharing (infant sleeping in a crib in parent's bedroom) is associated with a reduced risk of SIDS. The AAP recommends a separate but proximate sleeping environment.” *

Conclusions In Oregon, women who smoke are no less likely to bedshare than women who do not smoke, despite the increased risk of SIDS. The results for prenatal and postpartum smoking mothers are similar. All told 16% of the infants sometimes slept with mothers who smoked during and/or after pregnancy and 7% did so frequently. The results are similar across all ethnic and racial groups. Current epidemiological evidence cannot distinguish between risks associated with prenatal vs. risks associated with postpartum smoking. In Oregon, if not elsewhere, the message that smoking mothers should not bedshare is not being effectively disseminated.

Recommendations Greater public health efforts are needed to discourage either prenatal or postpartum smoking mothers from bedsharing. Bedsharing should be discouraged for infants less than 3 months of age, pending further research; young infants brought to bed to breastfeed should be returned to their crib for sleeping. There is little or no additional risk for infants > 3 months of age bedsharing with nonsmoking mothers and bedsharing conveys benefits to both mother and infant; the AAP recommendations go beyond what is scientifically supportable. Additional research is needed on the risks and benefits of bedsharing in adult beds by parents and infants, particularly regarding modifying variables (e.g. infant age, duration and frequency of bedsharing, breastfeeding, pacifiers, dangers of pillows/quilts/overheating).

References 1. Klonoff-Cohen H, Edelstein SL. Bed sharing and the sudden infant death syndrome. Br Med J 1995;311: Hauck FR, Herman SM, Donovan M, al. et. Sleep environment and the risk of Sudden Infant Death Syndrome in an urban population: the Chicago Infant Mortality Study. Pediatrics 2003;111: Brooke H, Gibson A, Tappin D, Brown H. Case control study of sudden infant death syndrome in Scotland, Br Med J 1997;314: Scragg RK, Mitchell EA, Taylor BJ, al. et. Bed sharing, smoking, and alcohol in the sudden infant death syndrome. Br Med J 1993;307: Mitchell EA, Tuohy PG, Brunt JM, et al. Risk factors for sudden infant death syndrome following the prevention campaign in New Zealand: a prospective study. Pediatrics 1997;100: Fleming PJ, Blair PS, Bacon C, et al. Environment of infants during sleep and risk of the sudden infant death syndrome: results of case-control study for confidential inquiry into stillbirths and deaths in infancy. Br Med J 1996;313: McGarvey C, McDonnell M, Hamilton K, O’Regan M, Matthews T. An eight-year study of risk factors for SIDS: Bedsharing vs. non bed-sharing. Arch Dis Child 2005 (doi: /adc ): Carpenter RG, Irgens LM, Blair PS, et al. Sudden unexplained infant death in 20 regions in Europe: case control study. Lancet 2004;363: Tappin D, Ecob R, Brooke H. Bedsharing, roomsharing, and Sudden Infant Death Syndrome in Scotland: a case-control study. J Pediatr 2005;147:32-7.

Published in Pediatrics Lahr MB, Rosenberg KD, Lapidus JA. Bedsharing and maternal smoking in a population-based survey of new mothers. Pediatrics. 2005;116:e530