Parent-infant bed-sharing:good or bad for babies?

George Haycock

Scientific Advisor

Foundation for the Study of Infant Deaths

Co-sleeping practices generally agreed to be dangerous

• Co-sleeping in a chair, couch or sofa

• Bed-sharing if:– mother is a smoker– mother has consumed alcohol (>2 units)– mother has taken sedative drugs– mother is excessively tired– the infant was premature or low birth weight

Bed-sharing: claimed advantages

• Reinforcement of breast feeding

• Promotion of mother-child bonding

• Improved quality of sleep– mother– infant

• Higher levels of arousability– mother– infant

Bed-sharing: possible hazards or disadvantages

• Increased risk of SIDS

• Increased risk of overlying or suffocation

• Overheating

• Poorer quality of sleep

Does bed-sharing lead to improved breast feeding rate and duration?

• Numerous studies have shown a definite correlation between breast feeding and bed-sharing

• It is very difficult to determine if this is because bed-sharing encourages breast feeding or because when women stop breast feeding they also stop bed-sharing

Does bed-sharing increase the risk of SIDS if mother is a non-smoker?

• Several studies from the UK and New Zealand found increased risk if mother was a smoker but not if she was a non-smoker

– Scragg et al 1993; Fleming et al 1996; Mitchell et al 1997; Blair et al 1999

• Other studies have suggested that there is a risk even if mother is a non-smoker, albeit much less than if she smokes

– Carpenter RG et al 2004; Tappin D et al 2005; McGarvey C et al 2006

• One study suggests that bed-sharing with persons other than parents (e.g. siblings) is a risk but not sharing with parents alone

– Hauck FR et al 2003

The ECAS StudyCarpenter RG et al. Lancet 363: 185-191, 2004

The ECAS StudyCarpenter RG et al. Lancet 363: 185-191, 2004

The ECAS StudyCarpenter RG et al. Lancet 363: 185-191, 2004

Carpenter noted that use of a duvet, and/or being found with the head covered, were not included in the multivariate analysis that resulted in the figures shown in Table 2. Because both of these might be associated with bed-sharing, he therefore reanalysed the data in a somewhat reduced data set in which this information was available, primarily to see whether including these variables removed the significance of the risk of bed-sharing for non-smoking mothers.

He also noted that the control group, i.e. the babies who did not bed-share, consisted of babies who were in their own cots either in the parents’ room or in a room of their own. Since the latter is known to be a risk factor compared with babies sleeping in a cot in their own rooms (OR 3.1), this was also included in the model.

The ECAS StudyCarpenter RG et al. Lancet 363: 185-191, 2004

Age (wks) OR Lower CI Upper CI

2 6.56 2.14 20.1

4 5.91 2.06 16.9

6 5.31 1.96 14.4

8 4.78 1.84 12.4

10 4.31 1.71 10.8

12 3.88 1.56 9.6

16 3.14 1.25 7.9

20 2.54 0.94 6.9

26 1.85 0.57 6.1

The ECAS StudyCarpenter RG et al. Lancet 363: 185-191, 2004

The ECAS StudyCarpenter RG et al. Lancet 363: 185-191, 2004

The ECAS StudyCarpenter RG et al. Lancet 363: 185-191, 2004

McGarvey C et al (2003) Factors relating to the infant’s last sleep environment in sudden infant death syndrome in the

Republic of Ireland. Arch Dis Child 88:1058-1064

• Co-sleeping was found to be a risk for babies of non-smoking mothers aged less than 16 weeks (Irish infants 1994-98: 152 cases, 620 controls).

• In this study as published, the co-sleeping group included both bed- and sofa-sharers.

• A further, so far unpublished, analysis was performed on an expanded data set (1994-2001) in which sofa sleepers were excluded. A significant risk was found for babies of non-smoking mothers aged under 16 weeks, OR 6.2: CI 1.88-20.61 (McGarvey C, personal communication).

McGarvey C et al (2006) An 8 year study of risk factors for SIDS: bed-sharing versus non-bed-sharing. Arch Dis Child 91:318-323

• The odds ratio for SIDS for bed-sharing infants whose mothers had smoked during pregnancy was 13.87 (9.58-20.09)

• The odds ratio for SIDS for bed-sharing infants whose mothers had not smoked during pregnancy was 2.09 (0.98-4.39)

• Bed-sharing remained a significant risk for babies aged 10 weeks or less after adjustment for maternal smoking

Tappin D et al. (2005) Bedsharing, roomsharing and sudden infant death syndrome in Scotland: a case-control study. J Pediatr 147: 32-37

A 1:2 case control study including 123 infants who died of SIDS between January 1 1996 and May 31 200, and 263 controls. Main outcome measure: sharing a sleep surface during last sleep

Tappin D et al. (2005) Bedsharing, roomsharing and sudden infant death syndrome in Scotland: a case-control study. J Pediatr 147: 32-37

• The highest risk was associated with couch sharing: OR 66.9 (2.8-1,596)

• Authors’ conclusions:– Bedsharing is associated with an increased

risk of SIDS for infants <11 weeks of age. Sharing a couch for sleep should be strongly discouraged at any age

Developmental Psychobiology 40: 14-22, 2002

Hunsley M, Thoman EBDevelopmental Psychobiology 40: 14-22, 2002

• 101 infants enrolled (45 male) at age 4 weeks• Studied twice, at 5 weeks and 6 months• Each study lasted 12 hours (7 pm – 7 am)• Motility Monitoring System

– Thin, pressure sensitive pad placed on the mattress– Signals sent via an amplifier to a 24 hour data logger

Hunsley M, Thoman EBDevelopmental Psychobiology 40: 14-22, 2002

• Infants classified as:– Long term co-sleepers

• Co-sleeping twice a week or more for at least 6 months

– Short term co-sleepers• Co-sleeping twice a week or more for less than 6 months

– Non-co-sleepers• Co-sleeping less than twice a week or not at all

Hunsley M, Thoman EBDevelopmental Psychobiology 40: 14-22, 2002

• Sleep/wake variables studied– Active sleep (AS)– Quiet sleep (QS)– Waking (W)– Active sleep bout length

• Mean duration of AS bouts during the recording– Quiet sleep bout length

• Mean duration of QS bouts during the recording– Arousals in active sleep– Arousals in quiet sleep

Hunsley M, Thoman EBDevelopmentalPsychobiology40: 14-22, 2002

Hunsley M, Thoman EBDevelopmental Psychobiology 40: 14-22, 2002

• Compared with non-co-sleepers, at 5 weeks and 6 months:– Long term co-sleepers showed:

• More QS• Longer bouts of QS

• At 6 months:– Long term co-sleepers showed:

• Less AS• Fewer arousals in AS• Less W

• Short term co-sleepers behaved in an intermediate way between long term co-sleepers and non-co-sleepers

Hunsley M, Thoman EBDevelopmental Psychobiology 40: 14-22, 2002

• These patterns, obtained during non-co-sleeping, were in marked contrast to the patterns seen during actual co-sleeping

• Co-sleeping infants showed:– Less QS– More arousals in QS– More sleep-stage shifts

• This pattern has been called sleep fragmentation– Kahn et al 1988; Roehrs et al 1994; Thoman & Whitney 1989

• Thus co-sleeping infants show extremes of sleep behaviour according to whether they are co-sleeping at the time or not

Hunsley M, Thoman EBDevelopmental Psychobiology 40: 14-22, 2002

• “Sleep fragmentation has been consistently associated with adverse conditions or consequences at all ages including:– Illness– Poor performance on cognitive tests– Negative developmental outcome”

• Anders & Roffwarg, 1973• Bonnet, 1986

• “This outcome could be expected as the result of the stress of repeated disruptions of an infant’s sleep that occur throughout periods of co-sleeping”

Parent-infant bed-sharing:good or bad for babies?

• Conclusions (1)– A beneficial effect on breast feeding is possible but

unproven– There is a very large increase in risk of SIDS

associated with couch or sofa sharing– There is a substantial increase in risk of SIDS for bed-

sharing infants of smoking mothers– There is a much smaller, but probably significant,

increase in risk of SIDS for bed-sharing infants of non-smoking infants at least in the first 2-3 months

– The different sleep patterns seen in bed-sharing infants as compared with non-bed-sharing infants are not necessarily advantageous to the infant

Parent-infant bed-sharing:good or bad for babies?

• Conclusions (2)– The advice currently given by the Foundation

for the Study of Infant Deaths, that the safest place to sleep your baby for the first 2 to 3 months of life is in a separate cot in the parents’ bedroom, is justified by available evidence

– It is certainly acceptable to take the baby into the mother’s bed to breast feed, but it is safest to return the baby to the cot after feeding

Dangers of the ‘Null Hypothesis’

• “Unfortunately any method which invites the contemplation of a ‘null’ hypothesis is open to grave misuse, or even abuse, and this seems particularly so in the social sciences, where high standards of objectivity are especially difficult to obtain, and data often of dubious quality”– Edwards AWF. Likelihood. Cambridge 1972

Dangers of the ‘Null Hypothesis’

• “What used to be called judgement is now called prejudice, and what used to be called prejudice is now called a null hypothesis. In the social sciences, particularly, it is dangerous nonsense (dressed up as ‘the scientific method’), and will call much trouble before it is widely appreciated as such”– Edwards AWF. Likelihood. Cambridge 1972