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Most Babies Who Died From SIDS Exposed To At Least One Risk Factor

March 29, 2012 1:37 p.m.


Dr. Henry Krous, lead researcher SIDS study, directs the San Diego SIDS Research Project at Rady Children's Hospital

Kitty Roche, public health nurse and San Diego County's SIDS coordinator

Related Story: Most Babies Who Died From SIDS Exposed To At Least One Risk Factor


This is a rush transcript created by a contractor for KPBS to improve accessibility for the deaf and hard-of-hearing. Please refer to the media file as the formal record of this interview. Opinions expressed by guests during interviews reflect the guest’s individual views and do not necessarily represent those of KPBS staff, members or its sponsors.

CAVANAUGH: This is KPBS Midday Edition. I'm Maureen Cavanaugh. The mysterious and tragic sudden infant death syndrome or SIDS has been researched for years by many, are including Rady Children's Hospital pathologist, Henry Krous. He is the author of a major paper published this week on a risk factor that seems to make babies more vulnerable to SIDS. I'd like to introduce my guests, Henry Krous is the author of the study on SIDS that was published this week in the journal pediatrics. And he is a pathologist at Reidy's children's hospital. Welcome to the show.

KROUS: Thank you.

CAVANAUGH: Kitty Roche is here too, a public health nurse, and San Diego County's SIDS coordinator. Kitty, welcome.

ROCHE: Thank you.

CAVANAUGH: Doctor Krous, why did you do this study on Sudden Infant Death Syndrome? If I recall directly, the incidence of SIDS dropped dramatically in the 1990s. Is it still going down?


KROUS: No, it's not. Historically, it's been about 1.5 per thousand light births. Then with the implementation of the back to sleep campaign in the early to mid-19-'90s, SIDS rates really deadlined dramatically and went down to about .5 nationally. Upon for the last five or six years, they've really plateaued, and we haven't seen any further deadline in the rates, which is distressing. We undertook this study to test the hypothesis of whether or not the profile of risk factors experienced by babies dying of Sudden Infant Death Syndrome had changed. Anticipating that it probably had as a result of the back to sleep campaign. What we found is that although the profile of risk factors had changed, the prevalence of risk factor, that is, the number of risk factors per baby that died of Sudden Infant Death Syndrome had not changed over the length of the study from 1991 through 2008. We found the incidence of prone sleep or tummy sleeping really went down from 85-30%. However, the incidents of other risk factor, bed sharing, and the baby sleeping out on a bed had actually doubled

CAVANAUGH: What you're saying if I may interrupt just a moment, is that the idea of placing an infant on his or her back to sleep, SIDS is actually more complicated than just doing that.

KROUS: It's far more complicated than that. And if you'll allow me, I will encapsulate quickly what we think Sudden Infant Death Syndrome is. And if you think of three circles, each representing an important area, and where all three circles would overlap, that's where we believe Sudden Infant Death Syndrome occurs. This is the so-called triple risk hypothesis. One of the circles is the age and governmental stage of the baby, the second circle are factors that are intrinsic to the baby, in other words things that either occur in the baby during its intrauterine life, and the third circle are factors that are under the control of a caretaker, and they have to do primarily with the sleep environment of the baby. Both SIDS deaths occur between the second and fourth month of life. Of and that's a period of very rapid physiological development and an Tommic growth. And as a result there are mechanisms of staying Alive, breathing, heart rate and so on, are quite unstable, particularly during sleep. Those factors that affect the baby after its birth are its male gender, premature birth, some genetic abnormalities that play out in abnormalities in serotonin metabolism in the brain stem, and exposure of the baby to alcohol or cigarette smoking as a result of the mother consuming those or being in that environment. You mentioned one of the most important, prone sleep or tummy sleeping. Others are just simply an unsafe sleep environment. The bed surface is very soft. Another is that the -- there may be excessive swaddling of the baby, there may be blankets over the baby. There may be overstuffed materials, pillows, bumper pads, toys in the bed. And so again, are it's when all thee of those areas intersect that a Sudden Infant Death Syndrome occurs.

CAVANAUGH: And I'm going to ask you to break that down for us in just a minute or two, especially about that third part of that interlocking circle, those things that parents can actually do to decrease the risk that their child might become a victim of SIDS. Now, you give a great deal of credit for this study to the San Diego County medical examiner's office. What information did they submit that makes this study unique?

KROUS: The San Diego medical examiner in compliance with some really critical legislation passed in the early 1990s, it is a very good medical examiner's office, very good pathologist, and they do very comprehensive examinations. And as a result of that legislation, are twenty-plus years ago, babies that die suddenly and unexpectedly are evaluated through the use of death scene protocols and autopsy protocols, and every baby that died in San Diego County during this study from 1991 to 2008 has been -- that was successioned by the medical examiner was successioned by this study. And without their systems, we would have never had this data. We're able to use this data to generate this really important study.

CAVANAUGH: Now, Kitty, you are the San Diego County SIDS coordinator. Can you tell us about how many children die from SIDS in San Diego each year?

ROCHE: Well, that number has really changed. When I first began to work in SIDS, which would have been in the late '80s, we had 60-75 babies a year that died of SIDS. After the back to sleep program, it actually decreased over the years. In 2010, we had 30, and in 2011, we had 15.

CAVANAUGH: I see. So those numbers are going down. But each of those 15 deaths is such an incredible tragedy for the family. How do you deal with families who have had a SIDS death?

ROCHE: Well, I consider it an honor to have worked with these families for this many years. The same -- doctor Krous was talking about in 1991 when the standardized autopsy laws became available in California that allowed him to do this study, the same laws put into place some systemic responses of families whose baby died of SIDS, and one of those was to institute a SIDS coordinator, and require special training for nurses or social workers to go out and visit these families with information about SIDS, what we know, help them understand be-Reavement, access them to resources in the community, including speaking with other SIDS parents, and just really try to reassure them in the ways that we can.

CAVANAUGH: And remind us, what are the ages where infants are most at risk?

ROCHE: Between two months and four months. But it's up to a year.

CAVANAUGH: Doctor Krous, as you say, the back to sleep campaign, placing infants on their backs to sleep, resulted in an enormous decrease in the number of SIDS deaths. But your research determined that where a baby sleeps is very important too. And you were just about to go into that, the idea of the surface of the bed, and the type of bed the infant is sleeping on. Tell us more about that.

KROUS: That's absolutely right. There's a tremendous emphasis now upon placing babies in a safe sleep environment. The profiling of the risk factors has changed, but the number of risk factors has not changed. I think that's one of the reasons that the rates have plateaued. Still, 30% of babies are placed on their stomach for sleep. So this sleep environment, which you asked me about, the safest possible place for a baby to sleep is alone in a crib with a well-fitting, firm mattress, without any other objects at all in the crib.

CAVANAUGH: How about blankets?

KROUS: No blanket, no toys, no bumper pads. There's clothing, the onesy that keep a baby warm, and that prevents any sort of material covering the baby's face, which is a risk factor for Sudden Infant Death Syndrome. I'd like to expand a moment on the bed sharing thing. This is a very important risk factor. One might assume that we are recommending against breast feeding. We are very much recommending that babies be breast-fed in every conceivable circumstance, absent some sort of medical contraindication to doing that. But at the same time, while we're not discouraging breast feeding, we're very much discouraging bed sharing.

CAVANAUGH: Because let me just make the link, a lot of women want to keep their babies in beds with them, during that time of very early infant hood of breast feeding to make it easier for a number of different reasons.

KROUS: Absolutely. Bonding.


KROUS: But there's no question, bed sharing imposing the maximum risk the younger the baby. And we recommend that the baby be placed on a separate sleep environment, but adjacent to the mother's bed. The baby can be brought into the bed for nursing, and then placed back on the separate sleep surface. We want them sleeping in the same room on a separate surface next to the mother's bed. This absolutely precludes any possibility that the baby would ever be accidentally overlane. Which we know occurs.

CAVANAUGH: Kitty, the idea that even after all the information that's been out for years now, 30% of infants are apparently placed on their stomachs for sleep, does hard to educate families about how to put their infants to bed so that they are les at risk of Sudden Infant Death Syndrome?

ROCHE: Well, we have an opportunity to do that, and all of the public health nurses in the county of San Diego that make home visits teach pregnant women, families that are expecting, and newly delivered families the safest way to sleep and give the reasons why we suggest that. In addition, we do outreach to perinatal care providers, specifically to nurses in the hospitals so they can role model the back to sleep. That's a really big piece of it. When they see it happen, they're more likely to do. There are lots of reasons why families continue to place babies prone. Some of it is there are many generations living in the home. And you all slept that way, and nothing happened to you.

CAVANAUGH: That's why the curious thing came up that having a grandmother in the home is actually a risk factor for SIDS. It's nothing of course to do with the grandmother herself. It's just that old habits my die hard about how to place the child in the crib.

ROCHE: Other times it's because they say the baby doesn't sleep well on the baby. And they just sleep better on their tummy. There are just lots and lots of reasons. We try really hard to work with the family on those risk factors they're willing to mitigate. And if we can get them to not put stuff in the crib, to all of that, then that's what we do.

CAVANAUGH: And so you have been starting even before this study, instructing new mothers and fathers to do what doctor Krous has been saying, just keep the infant on its back with nothing else in the crib but a tight-fitting mattress?

ROCHE: Correct. And in the colder weather, a sleep sack for -- to keep them warm. The latest American academy of pediatric recommendations for sleep have said even now bumper pads should be removed.

CAVANAUGH: Now, doctor Krous, these things that parents can do is just one of the risk factors in those three circles that you were telling us about before. Is part of your research what you found, that in the case of SIDS death that there's always more than one risk factor?

KROUS: No. Well, be yes, there is from the standpoint that -- let me say that about opinion% of the babies -- have at least one risk factor. The average baby has 3.5. And that's why we're emphasizing focusing on multiple risk factors be simultaneously avoided. Focusing on one just isn't enough. Prone sleep, 30% of babies still being put on their stomach, this really amplifies the responsibility that public health nurses, ped iatricians, family doctors, have to educate families taking home a new baby from the hospital. It also implies a responsibility on families with a new baby to seek out this information if they don't understand it clearly when they leave about caring for their baby to make sure it's in a max male safe environment.

CAVANAUGH: Are we any closer to knowing what actually physiologically is the cause of this Sudden Infant Death Syndrome what actually causes these infants to die?

KROUS: I think we're very, very much closer. We now know from a lot of research over the last 20 years that we've been collaborating with doctor Hannah Kinney at Harvard university in Boston that the vast majority of these babies have a clear abnormality of serotonin in their brain stem. They have abnormalities in other neurotransmitters. Neurotransmitters are little chemical pacts that transmit a signal from one nerve cell to another downstream. We've characterized many of the abnormalities in the way serotonin is synthesized, are packaged, released, transported, picked up by the next nerve cell downstream. How it is returned to the upstream nerve cell, but there's still an awful lots of work to do, not only with serotonin, to see how the different brain centers are connected both in terms of receiving signals that the baby is in trouble with a high carbon dioxide or a low oxygen level or in trouble because even if they recognize they're in trouble, they can't signal the baby to wake up to turn over, or whatever, to rescue itself. And then there are other neurotransmitters as well that deserve an equal amount of work, and that is yet to be done.

CAVANAUGH: And in the meantime, phoningsing on the risk factors is the thing that parents should do in order to keep their babies as safe as possible during those high-risk periods. Thank you both very much for speaking with us.

ROCHE: Thank you.

KROUS: Thank you.