CDC study does NOT show bed sharing is dangerous for infants
In what can only be described as an incredibly irresponsible publicity stunt, the Centers for Disease Control has sent out press releases claiming that a new study shows than infant bed sharing quadrupled the rate of infant suffocation and strangulation. The study, "US Infant Mortality Trends Attributable to Accidental Suffocation and Strangulation in Bed From 1984 Through 2004: Are Rates Increasing?" shows nothing of the kind. The overall rate of accidental unexplained infant suffocation and strangulation has not changed AT ALL. The only thing that has changed is the method of classifying infant deaths.
This finding is so important that it deserves to be repeated. There is NO evidence that sharing a bed with a parent increases the risk of accidental infant suffocation.
If there is no evidence that bed sharing increases the risk of infant suffocation, why did the CDC send out press releases suggesting that it does? A claim that parents are routinely suffocating their infants is much more likely to get publicity than merely pointing out that new guidelines for classifying unexplained infant death have led to more deaths being classified as unexplained suffocation and fewer deaths being classified as sudden infant death syndrome (SIDS). The total death rate did not change at all; only the classification changed.
This study does have important implications, but not the ones that the press release claimed. The study raises the possibility that the dramatic decline in SIDS attributed to putting babies on their back is not a real decline, but simply an effect of changing the classification of infant deaths.
Let’s look at what the study does not show:
The study does NOT show that there has been an increase in unexplained infant death. The rate of unexplained infant death has barely changed at all from 1998 to 2004.
The study does NOT show that there has been an increase in accidental suffocation or a decrease in SIDS. Both types of death appear the same on autopsy, therefore, there is no objective way to distinguish between the two after the death has occurred. The decision on how to classify the death is subjective, based purely on the decision of the person who filled out the death certificate.
The study does NOT provide a causal link between infant bed sharing and suffocation. There is no evidence in the study that bed sharing causes infant suffocation, because there is no objective evidence in the study of the actual cause of death. Moreover, the category of accidental suffocation is quite broad.
ASSB [accidental suffocation and strangulation in bed] includes suffocation by (1) soft bedding, pillow, or waterbed mattress, (2) overlaying or rolling on top of or against infant while sleeping, or (3) wedging and entrapment of an infant between 2 objects such as a mattress and wall, bed frame, or furniture; and strangulation by asphyxiation, such as when an infant’s head and neck become caught between crib railings.
In other words, most causes of death in this category have nothing to do with bed sharing at all.
So what really happened?
The authors themselves are quite honest about what they actually studied:
…Recent evidence showed that the decline in SIDS, from1998 through 2001, was offset by an increase in ASSB [accidental suffocation and strangulation in bed] and cause unknown deaths, suggesting that there has been a change in the way these [sudden unexplained infant deaths] are classified and reported…
In this study, we explored trends in infant deaths attributed to ASSB since 1984, before and after the release of the 1996 national guidelines, and assessed how the trend indicating fewer SIDS deaths might be explained by the trends showing increases in ASSB and cause unknown deaths…
What did the study actually show?
…[T]he overall [sudden unexplained infant death] rate showed no important increasing or decreasing trend from 1998 through 2004 …The pattern observed for the other [sudden unexplained infant death]-specific causes of death during this time did reveal an increasing trend for [accidental suffocation and strangulation in bed] and cause unknown and a declining trend for SIDS.
In other words, although the overall death rate remained the same, the proportion of deaths attributed to accidental suffocation rose, and the proportion attributed to SIDS declined concomitantly.
As the authors themselves point out:
The impressive decline in SIDS during the 1990s has been credited to national efforts promoting a supine sleep position for infants. Yet since 1998, safe-sleep prevention efforts may have had little effect in reducing total [sudden unexplained infant] deaths overall. Instead, the relatively stagnant total [sudden unexplained infant death] rate together with the observation that declining SIDS rates are being offset by increasing [accidental suffocation and strangulation in bed] and unknown cause rates suggests that the way these deaths are classified has changed. This change in classification and reporting has been observed in recent studies.
The following graph (modified from Figure 2 in the paper) makes this clear. Overall unexplained deaths have not change. The only thing that has changed is that the proportion of deaths attributed to accidental suffocation has increased while the proportion attributed to SIDS has declined by the same amount.
The author’s conclusions are quite modest:
Infant mortality rates attributable to ASSB have quadrupled in the last 2 decades, with the most dramatic increase in rates occurring after 1996. The reason for the increase is unknown …
It would be more accurate to add that it is also unknown if this represents a real increase or merely reflects a change in the classification. One thing is quite clear, however; this study does NOT show that infant bed sharing leads to an increased risk of accidental strangulation and it is irresponsible to suggest or imply that it does.