Parents who have lost a child to
sudden infant death syndrome (SIDS) may be suffering
unnecessary anxiety about the risks of a similar fate
befalling subsequent children, according to an Archives
of Disease in Childhood review published online
June 12. The analysis concludes that studies have consistently
overestimated the tendency of SIDS to run in families.
The British researchers argue that
failures to conduct autopsies in about half of the first
sibling deaths, failures to match cases with risk-adjusted
controls and failures to eliminate deaths from detectable
inherited conditions have fatally undermined research
to date.
INCIDENCE
DROP
Part of the problem stems from our success in getting
SIDS rates down. These have been halved in Canada since
1996. In Britain, where much of the available SIDS research
has been conducted, the rate was twice as high as Canada's
a decade ago but has fallen even more sharply.
Many of the available studies —
including most of the eight reviewed in the Archives
— predate these drops. Most even precede the sea
change that came with the recommendation to put infants
to sleep on their backs. All appeared before the detailed
understanding of risk factors that became available
after Britain wound up its Confidential Enquiry into
Stillbirths and Deaths in Infancy (CESDI) in 2000.
One consequence was that the earlier
researchers had no way to match babies whose elder siblings
had died to controls who had no such history but otherwise
had the same risk factors. This is a crucial failing,
because SIDS deaths are overwhelmingly concentrated
in families that have SIDS risk factors. Even after
behaviour is accounted for, there remains a hugely increased
risk of SIDS at the bottom of the socioeconomic ladder.
So if the case group consists mostly
of babies from disadvantaged families and the control
group does not, a study is bound to overestimate the
risk of second SIDS deaths. In fact, the authors say,
"if there is no stratification for risk, recurrences
in high-risk families would give rise to an apparent
(but spurious) doubling in overall recurrence rate."
EDUCATION
LINK
CESDI showed a whopping 40-fold difference in SIDS risk
between highest and lowest-risk families. This gap is
actually growing fast, as a direct result of our efforts
to educate parents on SIDS avoidance. It's a conundrum
of public health education campaigns that they tend
to enlarge the health gap between the comfortable middle
class and the poor, because only the middle class is
listening.
Research in Avon, England that
compared SIDS deaths before and after the government's
"Back to sleep" awareness campaign is revelatory. The
proportion of SIDS families in the lowest socioeconomic
categories was 47% before, but 74% after the campaign.
No future research on sibling SIDS
deaths is likely to produce valid results unless controls
are drawn from similarly at-risk groups. And, of course,
the existing research is called into doubt. These studies
predicted that families who had already lost one child
to SIDS were three to eight times more likely than average
parents to lose another.
The authors conclude that "a family's
risk for a second SIDS death is probably greater than
the risk for a first death," but "is almost certainly
less than that suggested by most of these studies."
Sally Clark was
later exonerated for the deaths of her two
infant sons |
"Meadows' Law" on SIDS recurrence
sent UK mothers to jail
SIDS recurrence was at the heart
of the famous murder conviction of British lawyer
Sally Clark for the smothering deaths of her two
infant sons. The testimony of pediatrician Sir
Roy Meadows — who famously declared the chances
of two SIDS deaths in one family to be one in
73 million — sent her and another mother
of two dead infants, Angela Cannings, to jail.
Sir Roy's claim was later disputed. Later evidence
claimed it to be more in the range of one in 200.
That number is now in doubt as well.
Both women had their convictions
overturned and the General Medical Council unsuccessfully
tried to have Sir Roy's licence revoked. Ms Clark
died in March under mysterious circumstances.
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