In the debate over ‘SIDS monitors,’ evidence is thin all around

Supporters hope modern baby monitors might prevent sudden infant death syndrome. Critics are doubtful. Who’s right?

Smart Sock Gen 3. Owlet photo

by Michael Schulson, Undark May 24, 2021

Each year in the United States, according to the Centers for Disease Control and Prevention, around 1,300 infants die from sudden infant death syndrome, or SIDS. It’s a leading cause of death for babies born without an obvious medical condition, and it is devastating in its particulars: Parents put a seemingly healthy infant down to sleep and come back to find that the baby has died. Most infants who die of SIDS are between 1 and 4 months old.

“The grief responses are especially severe,” said Richard Goldstein, a pediatrician at Boston Children’s Hospital who works with SIDS families. “They’re especially severe because it’s small, small children at a dependent age. And it’s especially severe because there’s no true explanation.”

Indeed, the causes of SIDS remain murky. In the early 1990s, researchers determined that putting infants down to sleep on their backs, rather than their sides or stomachs, lowered SIDS risk — potentially because stomach-sleeping may obstruct airflow, though the exact reasons are poorly understood. A “Back to Sleep” campaign pushed down the U.S. SIDS rate in the 1990s, but attempts to further reduce it have since stalled.

It is devastating in its particulars: Parents put a seemingly healthy infant down to sleep and come back to find that the baby has died. Most infants who die of SIDS are between 1 and 4 months old.

In recent years, however, some researchers and parents have hoped that increasingly sophisticated monitoring technologies might provide a crucial edge against an otherwise vexing syndrome. Monitoring sleeping infants for signs of cardiac or respiratory distress, the thinking goes, might offer warning signals for parents — and even let them intervene in the rare event that a baby begins to die.

Such hopes have helped to fuel a burgeoning market for high-tech baby monitors — often colloquially called SIDS monitors. These include devices like the Owlet Smart Sock, a Bluetooth-enabled sensor-equipped fabric sleeve, compact enough to slip over an infant’s tiny foot. When worn properly, the Utah-based health technology company suggests, the $299 garment will feed real-time data to parents’ phones on their baby’s heart rate, blood oxygen levels, and sleep patterns. Snuza, a South African company, makes a series of vital-data monitors that can clip to an infant’s diaper. Such monitors alarm when they detect a drop in a baby’s breathing or blood oxygen levels, and to date, each company has sold hundreds of thousands of units worldwide.

And yet, some scientists say, there is one thing that high-tech monitoring has not been proven to do: prevent SIDS.

While some device makers in this space traffic in SIDS information on their websites, and participate in SIDS awareness campaigns, they are careful not to market their wares as SIDS solutions — and for good reason: Many pediatrics experts argue that there’s little evidence that alarm-based monitoring wards off SIDS, and that past research has suggested that there are, in fact, no measurable warning signs that could identify an imminent case of SIDS and allow a parent to somehow intervene. Other analyses have even found some modern monitors to simply be inconsistent at monitoring anything, let alone detecting a potential onset of SIDS. These experts worry that monitors, no matter how elaborate or sophisticated, only provide parents with a false sense of security. In 2016, the American Academy of Pediatrics released official sleep safety guidelines recommending that parents “not use home cardiorespiratory monitors as a strategy to reduce the risk of SIDS.”

Supporters of these devices — as well as the monitoring companies themselves — argue that the AAP’s research is outdated, and doesn’t necessarily apply to current monitors on the market. The AAP guidelines, they point out, cite just four studies to back up their recommendation: Three from the 1980s, and a fourth published in 2001. That last analysis also specifically notes that it was “not designed to determine whether use of a monitor decreases the rate of SIDS.”

Greg Gallagher, the founder and CEO of Snuza, said the position of the AAP is out of step with technological advances that have accrued since the research AAP cites was published. “The AAP uses 35-year-old research to base their decision, or their stands, on,” Gallagher said. “A lot has changed in 35 years.”

And, both companies say that, at least so far, they have received virtually no reports of infants dying from SIDS while the monitors are in use.

But many pediatrics experts remain skeptical — particularly given that device makers like Owlet and Snuza keep their data close to the chest. And short of stronger evidence — ideally from a carefully controlled clinical trial — some pediatric experts continue to raise pointed questions about what, exactly, modern monitoring companies are selling. Ruey-Kang Chang, a pediatric cardiologist at Harbor-UCLA hospital who has published research on SIDS, said it’s clear that there is no clinical trial data or scientific evidence that shows these monitors can save babies from SIDS. Instead, he said, “I think they prey on parents’ anxiety.”

SIDS is what doctors call a diagnosis of exclusion: Coroners list it as the cause of death when a child unexpectedly dies in their sleep before reaching one year of age, and all other possibilities have been ruled out. (Another category of unexpected deaths, sometimes conflated with SIDS, is caused by accidental suffocation in the crib).

Over the years, researchers have proposed a huge range of explanations for the sudden deaths. Theories have included undetected viral infections, magnesium deficiency, diaphragm failure, various heart defects, and abnormalities in the brainstem. Sometimes, a breakthrough will explain some subset of SIDS cases. For example, some infants who were once thought to die from SIDS are now known to have a metabolic disorder called medium-chain acyl-CoA dehydrogenase deficiency.

Epidemiologists have also identified factors that are linked to higher risk of SIDS. Babies born prematurely are at elevated risk, as may be those with a sibling who died from SIDS. And, at least in the United States, parents who are poor, who are Black or Native American, or who smoke are all likelier to lose an infant to SIDS. (There are likely multiple factors driving those racial and class disparities, and the exact causes remain unclear. Researchers have suggested that they could stem from uneven adherence to sleep guidelines, or from unequal access to medical care).

“The AAP uses 35-year-old research to base their decision, or their stands, on,” Gallagher said. “A lot has changed in 35 years.”

For years, one hypothesis was that SIDS emerged from a form of sleep apnea — long pauses in breathing, of unknown origin, that sometimes proved fatal. The theory rested, in part, on a landmark 1972 study by Alfred Steinschneider, a physician-researcher in upstate New York. Over the course of several years, Steinschneider monitored the breathing of five infants, thought to be at elevated risk of SIDS, while they slept. Two of them — siblings from a family that had previously experienced unexplained deaths — showed prolonged bouts of apnea. Each died at home soon after, and Steinschneider concluded that the evidence supported the hypothesis that sleep apnea caused SIDS. He suggested physicians might monitor high-risk infants for apnea in order to detect those signs of troubled breathing, and in the decades that followed, high-risk infants were sometimes sent home with bulky cardiorespiratory monitors, which fit under the crib mattress and required parents to affix a band around the infant’s chest during sleep. The set-up was challenging for parents and often generated false alarms. But it could, at least in theory, alert parents and physicians to troubled breathing.

By the 1990s, though, support for such monitoring was foundering. Steinschneider’s seminal paper fell apart in 1994, when the mother of the two infants who were thought to have died from SIDS confessed to murdering them. (Studies suggest that a small percentage of deaths attributed to SIDS are actually infanticides).

A major study in the 1990s, called the CHIME study, sent home monitors with more than 1,000 infants, searching for a link between disrupted breathing and SIDS risk. After sifting through data from 700,000 hours of monitoring, the team found that erratic or disrupted breathing events were common across all groups of infants, whether or not they were at high risk for SIDS. “Events previously described as ‘pathologic,’” the study concluded, are actually quite common, even in healthy term infants.”

Whatever it was that made the high-risk kids likelier to die from SIDS, the researchers argued, they did not seem to have uniquely obstructed breathing. There was “no ability to distinguish them through monitoring, to separate one group from another,” said George Lister, a professor of pediatrics at the Yale School of Medicine and an author of the CHIME study.

The CHIME study — which is cited in the most recent AAP guidelines — examined whether troubled breathing was a warning sign for SIDS. It was not designed to show whether a monitor, by alarming, would allow parents to interrupt a fatal event in progress. (Two infants died of SIDS during the CHIME study, but neither was being monitored at the time).

Ruey-Kang Chang, a pediatric cardiologist, said it’s clear that there is no clinical trial data or scientific evidence that shows these monitors can save babies from SIDS. Instead, he said, “I think they prey on parents’ anxiety.”

Still, the evidence convinced many pediatrics experts that monitoring respiration for signs of SIDS probably wasn’t worth it. Among them was Rachel Moon, a pediatrician and SIDS expert at University of Virginia Health who oversaw the AAP guidelines. “There’s no technology that’s going to tell you if a baby’s going to die,” she said. “Because there’s no warning signs that we know of.”

One pediatrician who has continued to argue that monitoring has value is Gary Freed, who worked briefly with Steinschneider in the 1990s. Freed went on to start the apnea center at Children’s Health Care of Atlanta, which he ran for 20 years. The center would send high-risk infants home with monitors, and keep an eye on the data to look for issues that, they feared, could lead to a sudden death.

The experience convinced Freed that monitoring can help catch medical problems. Data that Freed and three colleagues published as part of a commentary in The Journal of Perinatology in 2002, summarizing results from more than 8,000 apnea center patients, suggested that babies in the program died from SIDS at lower rates than in the general population — even though they were considered high-risk. Of the five that had died from SIDS, only one was connected to the monitor at the time of death. (Freed has collaborated with Owlet on a paper but does not recall receiving compensation).

“If a kid’s not breathing for more than 30 seconds,” Freed said, “I would like to know, if that was my kid.”

Gallagher, the founder of Snuza, is an engineer with a background in microcontrollers — simple, tiny computers used in consumer electronics and medical devices. In 2003, he began designing a small, wireless tool that could monitor an infant’s breathing and movement. His company, based in Cape Town, sold its first unit in 2007. “We have been proven, and we claim, that we are able to detect the cessation of breathing in infants,” said Gallagher. He said they have sold hundreds of thousands of units worldwide, including their best-selling product, the Snuza Hero, which is certified under the European Medical Devices Directive.

Snuza’s devices clip onto a baby’s diaper, or onto the waistband of pajama pants. If the Hero does not record breathing for 15 seconds, it buzzes, attempting to wake the baby. After 5 more seconds without a breathing signal, an alarm goes off for the parents.

The Owlet Smart Sock, conceived by a group of students at Brigham Young University in Utah, is a home-based pulse oximetry monitor — a tool that uses beams of light to estimate the level of oxygen in the blood. If oxygen levels appear to drop, the sock sets off an alarm. Since shipping its first product in 2015, the company says, it has sold more than 1 million units.

Some online reviewers credit the monitors with saving their babies. “Snuza Go literally saved my baby’s life!” one review at the online retailer Amazon begins, explaining how the parents heard the alarm, found their baby unresponsive, and successfully used CPR to resuscitate her. Those kinds of stories have won over some advocates, including Karl Waddell and Alex Hamilton, who co-founded River’s Gift, an Australian nonprofit that funds SIDS research and promotes safe-sleep practices, after the sudden death of their 4-month-old son, River, in 2011.

In a Zoom interview, Waddell acknowledged that “there’s no scientific evidence to suggest and to display that an alarm-based monitor will avert a SIDS case or a sudden unexpected infant death in sleep.” But, he continued, “we strongly believe that there are instances where alarm-based monitors would have and will save the lives, just through anecdotal evidence as much as anything.”

River’s Gift retails Owlet products on its website, and Waddell has attended a gathering for SIDS parents hosted by Owlet at its Utah headquarters. River’s Gift recommends the use of monitors to parents, and Waddell said he and Hamilton used them with their second and third children.

Waddell said they’d heard of “a number of incidents” in which the alarm on a baby goes off, and “the parent or guardian has gone to their side to discover they might be blue, or they might not be breathing.”

“And then when they’re picked up or they’re prompted, they take a big deep breath,” he added. “That’s enough evidence for us.”

Leading SIDS experts, though, just aren’t convinced that such monitors work well — or that they’re even the best potential approach for using monitoring technology to reduce SIDS risk.

Some of those concerns revolve around the question of whether the monitors reliably alarm. In 2017, a study at the Children’s Hospital of Philadelphia, or CHOP, subjected the Owlet and another home-based pulse oximeter, the Baby Vida, to a round of tests. The team examined whether the devices could identify hypoxemia, or a below-average level of oxygen in the blood. The second-generation Owlet, the team found, “detected hypoxemia but performed inconsistently” compared to a hospital-grade monitor. The Baby Vida “never detected hypoxemia and also displayed falsely low pulse rates,” the team wrote.

Moon, the UVA pediatrician, cited the CHOP study in explaining the committee’s continued skepticism of such products. “We know the hospital grade monitors don’t work,” she said, “so why would we recommend something that’s worse than what the hospital grade monitors can do?”

Jordan Monroe, an Owlet co-founder and executive, said the company disputes the CHOP team’s findings, and that the researchers did not use the product as intended. Christopher Bonafide, the CHOP pediatrician who led the study, did not respond to interview requests.

Experts have also questioned whether an alarm, even if does alert parents to an emergency, would actually give parents much of a chance to resuscitate the baby. Goldstein, at Boston Children’s Hospital, acknowledged that some parents may respond to the alarm to find a baby in apparent respiratory distress. But, he continued, that’s not always the same thing as SIDS, or even necessarily life threatening.

The most promising recent research on SIDS, he said, suggests that many cases involve a neurological issue that produces “a sort of uncoupling” between the way the heart and the lungs respond to a need for oxygen. “That’s not really resuscitatable,” he said. “You don’t respond to your baby and shake them out of it. It’s a genuinely terminal event.” (Goldstein has been involved with some research on that issue at Harvard).

“We know the hospital grade monitors don’t work,” Moon said, “so why would we recommend something that’s worse than what the hospital grade monitors can do?”

Chang, the pediatric cardiologist, raised similar concerns. “When a baby stops breathing, there’s not much time to intervene,” he said, adding that even well-trained physicians struggle to resuscitate infants through CPR. Chang argues that, instead of tracking babies’ physiological signs, monitors should actually track the environment around babies, alerting parents when conditions associated with a higher risk of sudden death, such as higher temperatures or a breathing obstruction, are present. In 2015, Chang filed a patent for such a monitor, but the project stalled. As for tools like Snuza and Owlet, he said, “I doubt any of the baby monitors will work, ever, because they focus on monitoring the babies. And it’s very late when things are not going well.”

Still, companies say they have data suggesting the devices lower SIDS rates — even if, to avoid scrutiny from medical device regulators, they have to be careful how they describe it.

Monroe, the Owlet co-founder, initially declined to speak on the record about the company’s internal mortality records, citing legal concerns. Shortly before this piece went to publication, however, he sent an email offering more detail. “Although we have monitored nearly a million babies and hear from parents on a daily basis, we have not received any reports of a baby passing away while being actively monitored by the Smart Sock,” Monroe wrote. “However, just because there is an absence of reports does not necessarily mean that there has not been an incident.”

The company, he added, is “actively investigating this lack of reports and working with third-party researchers to perform scientifically sound and data-driven analyses before making any kind of claim about the life-saving potential of the Smart Sock.”

Gallagher, the Snuza founder, described similar outcomes. “Out of the 350,000 devices that we have looked at, we’ve had one reported death,” he said. “And that death, the parents were alerted, but they couldn’t resuscitate the baby.” Meanwhile, he said, Snuza has “many dozens” of testimonials from parents reporting that the product saved their babies’ lives. Given data suggesting that roughly one in 3,000 babies die from SIDS every year in the U.S., that would seem to be a promising metric.

But Moon doesn’t put much stock in the companies’ internal data. “I don’t think we can extrapolate anything from that,” she said. “I know, myself, of two babies who have died while they have had one of these monitors on, and I know this because the parents have called me to ask me about why their baby died if the monitor was on.” In both cases, she said, the monitor manufacturer claimed to have no record that the product was on at the time of death.

Moon worries that monitors will give parents a sense of invincibility, and perhaps make them more comfortable straying from safe-sleep guidelines. (Monroe, while stressing his support for safe sleep practices, was skeptical of that concern. “I put my kids in a car seat,” he said, “but that doesn’t mean I drive faster).”

One thing the companies have not yet done is actually publish their internal data on mortality, or subject it to the rigors of peer review. Goldstein would welcome a chance to see such data. “Yeah, I mean, bring it on,” he said. “We have statistical methods that help us evaluate whether a claim or observation occurs by chance, or if they actually have enough observations to claim anything.”

One way to settle the question, experts say, would be a randomized controlled trial: Some infants get monitors, some don’t, and researchers then track whether SIDS rates are lower among monitored infants. Actually doing that research, though, could be ethically complicated and prohibitively expensive. Because SIDS is so rare, the study would likely need to enroll a huge number of families — “hundreds of thousands of babies,” Moon estimated — in order to collect enough data to discern a pattern.


For some parents, though, the question of monitors is as much about how to deal with the anxiety — and uncertainty — of parenthood as it is about the data. Goldstein works closely with parents who have lost a child to SIDS. Sometimes, if those parents go on to have another child, they find themselves unable to sleep, spending long nights watching over their baby. If a monitor “actually might let you get a few feet away from the crib and sleep,” Goldstein said, “well, that’s a different kind of an idea.” These parents, he continued, understand the monitors won’t prevent SIDS. “But they are also exhausted,” he said. “And it helps them in that way.”

In many cases, as even advocates of the technologies will acknowledge, high-tech monitors target the pocketbooks — and perhaps the anxieties — of the families least at risk. Alarm-based monitors cost hundreds of dollars. They appear to target affluent new parents, whose babies are at the lowest risk of SIDS.

“One of the issues is that the people who buy the monitors are the people who are privileged, and the people who have a lot of money,” said Moon. “And we know that the babies, at least demographically, are at high risk, have no access to these.”

When it comes to societal investments in reducing SIDS rates, Moon calls for better public health campaigns to help raise attention to common risk factors for SIDS that persist in many homes — including smoking and co-sleeping with infants. Goldstein, too, calls not for consumer-oriented solutions, but for more big-picture thinking. Even if the exact connections aren’t clear, poverty and racism and other disparities seem to inflect SIDS rates. “If I had to put my money anywhere,” he said, “that’s what I would do: I would reduce disparities, and I would increase access to medicine.”

UPDATE: This piece has been updated to note that the Snuza Hero is certified by the European Medical Devices Directive.
Michael Schulson is a contributing editor for Undark. His work has also been published by Aeon, NPR, Pacific Standard, Scientific American, Slate, and Wired, among other publications.

This article was originally published on Undark. Read the original article.

  Further reading

Detection of Tachyarrhythmias in a Large Cohort of Infants Using Direct-to-Consumer Heart Rate Monitoring, Anjewierden S, Humpherys J, LaPage MJ, Asaki SY, Aziz PF. J Pediatr. 2021 May;232:147-153.e1. doi: 10.1016/j.jpeds.2020.12.080. Epub 2021 Jan 6.

Smartphone app for neonatal heart rate assessment: an observational study, Myrnerts Höök S, Pejovic NJ, Cavallin F, Lubulwa C, Byamugisha J, Nankunda J, Tylleskär T, Alfven T. BMJ Paediatr Open. 2020 Jul 22;4(1):e000688. doi: 10.1136/bmjpo-2020-000688. Full text

Cardiorespiratory sleep studies at home: experience in research and clinical cohorts, Kingshott RN, Gahleitner F, Elphick HE, Gringras P, Farquhar M, Pickering RM, Martin J, Reynolds J, Joyce A, Gavlak JC, Evans HJ, Hill CM. Arch Dis Child. 2019 May;104(5):476-481. doi: 10.1136/archdischild-2018-315676. Epub 2018 Nov 19.

Accuracy of Pulse Oximetry-Based Home Baby Monitors, Bonafide CP, Localio AR, Ferro DF, Orenstein EW, Jamison DT, Lavanchy C, Foglia EE. JAMA. 2018 Aug 21;320(7):717-719. doi: 10.1001/jama.2018.9018.

A New Way Of Monitoring Infants At Home, Gary E. Freed. Neonatology Today. August 2018 pg.12-18. PDF

Neonatal Monitoring: Prediction of Autonomic Regulation at 1 Month from Newborn Assessments, In: SIDS Sudden Infant and Early Childhood Death: The Past, the Present and the Future, Duncan JR, Byard RW, editors. Adelaide (AU): University of Adelaide Press; 2018 May. Chapter 21.

Initial Experience and Usage Patterns With the Owlet Smart Sock Monitor in 47,495 Newborns, Dangerfield MI, Ward K, Davidson L, Adamian M. Glob Pediatr Health. 2017 Dec 4;4:2333794X17742751. doi: 10.1177/2333794X17742751. Full text

The History of Home Cardiorespiratory Monitoring, Freed GE, Martinez F. Pediatr Ann. 2017 Aug 1;46(8):e303-e308. doi: 10.3928/19382359-20170725-01.

SIDS-CDF Hypothesis Revisited: Cause vs. Contributing Factors, Siren PM. Front Neurol. 2017 Jan 16;7:244. doi: 10.3389/fneur.2016.00244. Full text

SIDS and Other Sleep-Related Infant Deaths: Evidence Base for 2016 Updated Recommendations for a Safe Infant Sleeping Environment,  Moon RY; TASK FORCE ON SUDDEN INFANT DEATH SYNDROME. Pediatrics. 2016 Nov;138(5):e20162940. doi: 10.1542/peds.2016-2940. Full text, PDF

Research: Comparison of the Accuracy of a Pocket versus Standard Pulse Oximeter, da Costa JC, Faustino P, Lima R, Ladeira I, Guimarães M. Biomed Instrum Technol. 2016 May-Jun;50(3):190-3. doi: 10.2345/0899-8205-50.3.190.

Pulse oximetry measures a lower heart rate at birth compared with electrocardiography, van Vonderen JJ, Hooper SB, Kroese JK, Roest AA, Narayen IC, van Zwet EW, te Pas AB. J Pediatr. 2015 Jan;166(1):49-53. doi: 10.1016/j.jpeds.2014.09.015. Epub 2014 Oct 14.

Comparison between pulse oximetry and transthoracic impedance alarm traces during home monitoring, Nassi N, Piumelli R, Lombardi E, Landini L, Donzelli G, de Martino M. Arch Dis Child. 2008 Feb;93(2):126-32. doi: 10.1136/adc.2007.118513. Epub 2007 Sep 24.

Effect of home monitoring on a high-risk population, Freed GE, Meny R, Glomb WB, Hageman JR. J Perinatol. 2002 Mar;22(2):165-7. doi: 10.1038/sj.jp.7210662.

Cardiorespiratory events recorded on home monitors: Comparison of healthy infants with those at increased risk for SIDS, Ramanathan R, Corwin MJ, Hunt CE, Lister G, Tinsley LR, Baird T, Silvestri JM, Crowell DH, Hufford D, Martin RJ, Neuman MR, Weese-Mayer DE, Cupples LA, Peucker M, Willinger M, Keens TG; Collaborative Home Infant Monitoring Evaluation (CHIME) Study Group. JAMA. 2001 May 2;285(17):2199-207. doi: 10.1001/jama.285.17.2199.

Prolonged apnea and the sudden infant death syndrome: clinical and laboratory observations, Steinschneider A. Pediatrics. 1972 Oct;50(4):646-54. Erratum Pediatrics. June 1994, 93 (6) 944. PDF

Sudden infant death syndrome (SIDS), apnea, and near miss for SIDS, Valdes-Dapena M, Steinschneider A. Emerg Med Clin North Am. 1983 Apr;1(1):27-44.

The sudden infant death syndrome and apnea/obstruction during neonatal sleep and feeding, Steinschneider A, Weinstein SL, Diamond E. Pediatrics. 1982 Dec;70(6):858-63.

Blind-spot-Nature-s41390-021-01508-4

Blind spot, Siren PM. Pediatr Res (2021). doi: 10.1038/s41390-021-01508-4

Also see
Ways to reduce the risk of SIDS and other sleep-related causes of infant death Eunice Kennedy Shriver National Institutes of Child Health and Human Development NICHD
How can I reduce the risk of SIDS? Eunice Kennedy Shriver National Institute of Child Health and Human Development NICHD
How to Keep Your Sleeping Baby Safe: AAP Policy Explained American Academy of Pediatrics
Safe Sleep: Recommendations American Academy of Pediatrics
Researchers Warn Parents About Using Monitors to Prevent SIDS Following Study People
Does Your Baby Need a SIDS Monitor? Parents
Did a Murderer in Waiting Go Undetected Because She Was a Woman? The New Yorker
Are High-Tech Baby Monitors Worth It? Even Safe? Grow by WebMD
New type of baby monitors offers ‘peace of mind’ but may deliver just the opposite The Washington Post
Owlet Baby Care Responds to CHOP Study’s Accuracy Claims Biospace

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