Cause of Sudden Infant Death Syndrome remains elusive

Saturday, April 21st 2001, 12:00 am
By: News On 6

CHICAGO (AP) _ The leading killer of American babies is a medical mystery, but its victims die with heartbreaking familiarity: An apparently healthy infant is put to bed and slumbers peacefully. In the morning, he is dead.

Despite decades of research, scientists remain confounded. Sudden Infant Death Syndrome steals more small lives each year than cancer, pneumonia, heart disease and AIDS combined.

It has a name, but no one knows how it works.

``The story is now 40 years old and we're still trying to figure out what it is _ let alone how to treat it and how to prevent it,'' said Dr. Henry Krous, a SIDS expert at Children's Hospital of San Diego.

Coined at a medical conference in the late 1960s, SIDS described unexpected deaths that even autopsies couldn't explain. It kills nearly 3,000 infants yearly, a disproportionate number of whom are black. It also is mistakenly blamed in a small number cases where parents have killed their children.

Some think SIDS has several causes, but many researchers now favor a theory that brain stem defects somehow affect arousal reflexes, leaving babies especially vulnerable when sleeping on their stomachs.

In the 1990s, a nationwide public health initiative instructed parents to place sleeping infants on their backs, thereby reducing the chance of smothering. The number of SIDS deaths declined significantly in that decade. Now, however, the numbers have flattened, surprising researchers and reigniting their passion to find a cause.

Many are gathering April 21-23 in suburban Chicago at the SIDS Alliance national meeting to compare notes and offer what advice is available on this bewildering syndrome.

The death of Dominic Miller eight months ago is typically baffling.

Dominic was 4 1/2 months when he died during the summer, though most SIDS deaths occur in winter and fall. Ninety percent occur between the ages of two months and six months.

Mother Kathleen Miller, of West Peoria, Ill., says her son had been ``laughing and cooing and smiling'' before she put him to bed on Aug. 9. Aware of the link between SIDS and stomach-sleeping, she said she carefully laid Dominic on his back.

When her husband, Marc, checked his son just 20 minutes later, Dominic was face down, limp and not breathing. His body was still warm, but bloody foam surrounded his nose, meaning his vital organs had shut down _ a telltale sign of SIDS.

Paramedics and doctors at the local hospital couldn't revive him.

``It's like the ultimate shock,'' Mrs. Miller, 27, said. ``You just go from a totally healthy baby to 20 minutes later he's gone; to two hours later (asking) can we donate his organs.''

Though it was once known as crib and cot death, SIDS can afflict babies sleeping on any surface.

The last big breakthrough occurred nearly a decade ago, after researchers discovered the high SIDS risk to babies who slept on their stomachs.

It prompted the American Academy of Pediatrics to recommend in 1992 that babies sleep on their backs. The academy helped launch a nationwide ``Back to Sleep'' campaign two years later, and SIDS deaths dropped 40 percent _ from 4,660 in 1992 to about 2,800 in 1998. The numbers have remained fairly constant.

Autopsies are recommended after all SIDS deaths, but typically they reveal the same sparse information as Dominic Miller's. The baby had pinhead hemorrhages in his lungs, but nothing else.

The tiny bleeding spots, called petechiae, are found in many SIDS babies and in other ailments as well. With SIDS babies, Krous suspects the hemorrhaging is caused by vigorous but futile efforts to resume breathing after a period of sleep apnea, when breathing stops for a few seconds.

Most babies rouse themselves easily from such episodes, which are normal. But the leading SIDS theory suggests that affected babies have subtle brain-stem abnormalities that block normal arousal or alarm reflexes.

Dr. Hannah Kinney, a neuropathologist at Harvard and at Children's Hospital in Boston, developed his theory during several years of research on animals and infants.

Kinney says certain babies are born with chemical defects in the lower portion of the brain stem called the ventral medulla, which is involved in alarm reflexes. It regulates blood pressure and breathing during sleep, and controls how the baby responds to low oxygen blood levels and high amounts of carbon dioxide.

Lack of oxygen and excessive carbon dioxide can occur when a baby is sleeping on his or her stomach, or face down. Normal babies rouse and turn their heads. Kinney says many SIDS babies can't ``respond to the challenge.''

She suspects the problem may arise during fetal development.

The defect has no symptoms. Kinney hopes sophisticated tests that detect it will eventually become part of routine autopsies. Her ultimate goal, which will take years, is to devise a blood test that detects the abnormality before it kills, and to learn whether factors such as nutritional deficiency during pregnancy are a cause.

Kinney decided to specialize in SIDS research after dealing with the parents of dead babies during her medical training.

``It was very difficult to say I don't know what's involved. I don't have any answers,'' she recalled.

Dr. Warren Guntheroth of the University of Washington says some SIDS deaths are caused by particular vulnerability to heat stress, which is most likely to occur when babies are on their stomachs and over-swaddled. The main symptom is sweating, but body temperature doesn't have to rise for the stress to be life-threatening, Guntheroth says.

In an article in April's Pediatrics journal Guntheroth said a public campaign warning about heat stress, similar to the ``Back to Sleep'' push, may help reduce SIDS deaths.

And in recommendations published last year, the American Academy of Pediatrics listed overheating and excessive use of blankets or bed clothes among factors that increase the risk of SIDS.

At Rush Presbyterian-St. Luke's Medical Center in Chicago, Dr. Jean Silvestri is studying infants considered to be high-risk for SIDS, including premature babies and those who've had several life-threatening breathing lapses during sleep.

Some infants are given portable sleep monitors for home use, which sound an alarm if breathing becomes erratic. Silvestri's research has found such episodes are common, even in healthy infants, but life-threatening lapses occur mostly in premature babies.

Five-month-old Kamari Jackson, a boy born more than a month early weighing under three pounds, is one of her patients.

Silvestri goes through a checklist of SIDS risk factors with his mother, Kenisha Stallworth. Any smokers in the home? Family history of SIDS? Does he sleep in a crib with a firm mattress, without pillows or soft crib toys?

Stallworth smiles sheepishly and admits to sometimes bringing the baby in bed with her ``when he whines a little too much.''

Bed-sharing is another risk factor, and Silvestri gently reminds the young mother that her child is already at risk.

Stallworth, who is black, knows to put Kamari to sleep on his back.

But research has found the ``back-to-sleep'' campaign failed to reach many African-American communities, and some experts think that explains why black babies are nearly three times more likely to die of SIDS than whites.

A recent public awareness campaign that included home-visits to at-risk families in Chicago's minority neighborhoods helped turn things around, said Shirley Fleming, Chicago's deputy public health commissioner.

It resulted in a 37 percent drop in SIDS deaths among Chicago blacks, from 56 deaths in 1998 to 35 in 1999.

In the Netherlands, where health care is universal and nearly all new parents receive home visits from caregivers who promote back-sleeping, there are just 27 SIDS deaths a year out of 200,000 births, said Dutch researcher Monique L'Hoir, a presenter at the conference.

That's nearly eight times lower than the U.S. rate of 3,000 out of 3 million. Silvestri also is studying similarities between SIDS and rare disorders of respiratory control, some of which are thought to have genetic causes.

But whether SIDS, too, is hereditary is ``a major, major quagmire,'' Silvestri said.

The controversy stems from a nearly 30-year-old theory suggesting that SIDS runs in families, based primarily on research of five siblings in upstate New York who all purportedly died of SIDS. Their mother later was convicted of smothering them.

Critics claim the theory caused some murders to be misclassified as SIDS.

While acknowledging that only a small portion of SIDS cases are likely to be murders, the American Academy of Pediatrics recently issued guidelines recommending a child-abuse expert be part of all SIDS investigations.

Desperate to find a cause, parents of SIDS babies typically want thorough investigations. But some say overzealous law enforcement and ignorance about SIDS makes them feel like criminals,

Charlene Melcher, 38, of Orlando, Fla., whose 7-week-old son, Jason, died of SIDS in 1998, says police told her husband: ``You had to have done something to him because healthy babies don't die.''

That kind of suspicion ``really sets you back,'' she said.

But like most SIDS parents, Melcher says the hardest part is not knowing the cause. She'll be going to the Chicago conference with hopes of finding answers.

``It's been two years and I still daily search for answers, for a reason why,'' she said.

``The autopsy report shows he was a perfectly healthy baby. That's hard to live with,'' Melcher said. ``If all his organs were perfect, why isn't he here with me?''