Promising research about cause of SIDS

  • Parents of newborns and infants are asked to continue to follow SIDS precautions, especially placing a baby younger than 1 year old on its back for sleep.

    Parents of newborns and infants are asked to continue to follow SIDS precautions, especially placing a baby younger than 1 year old on its back for sleep. Stock Photo

By Dr. Eve Glazier and Dr. Elizabeth Ko
Posted7/9/2022 6:00 AM

Q: Is it true a new study figured out what causes SIDS? My sister lost her baby daughter that way, and even though it was almost eight years ago, our family is still struggling. It would help if we could understand what actually happened.

A: Sudden infant death syndrome, or SIDS, is the sudden and unexplained death of an otherwise healthy baby. Because it often occurs during sleep, it is also known as crib death. It's a devastating experience, and as with your own family, the shock and pain can reverberate for years, and even an entire lifetime.


SIDS is the leading cause of death in the United States among infants between 1 month and 1 year old. The majority of SIDS deaths occur in babies 6 months and younger, but it can happen any time during the baby's first year.

What makes this type of loss particularly difficult is the inability to pinpoint a cause. There is evidence that multiple factors are at play in SIDS. This includes a possible deficiency in an area of the brain that controls heart rate, breathing and waking from sleep. However, a definitive answer is not yet clear.

A public health campaign that urged parents to position sleeping babies on their backs led to a 50% drop in SIDS deaths since the 1990s. But even with those precautions, the syndrome continues to take the lives of more than 1,200 infants in the U.S. each year.

Your question refers to a recent small study, conducted by researchers in Australia, that has shed new light on this heartbreaking mystery. When they analyzed dried blood samples obtained from the heel pricks of 655 healthy newborns, the researchers found a key difference in most of the babies who later died from SIDS. Specifically, those babies had lower blood levels of an enzyme known as butyrylcholinesterase, or BChE. This enzyme, which is produced by the liver, plays an important role in chemical processes that allow the brain to send instructions to wake up.

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Finding lower blood levels of BChE adds weight to the idea that some babies die of SIDS because their brains can't send the necessary "wake-up" signals to arouse them in a dangerous situation. This is the first time someone has isolated a biochemical marker that is potentially associated with SIDS.

However, due to the small size of the study, and some ambiguous data points, it's not yet possible to know if testing for BChE would be effective.

As with any screening tool, it's important to establish a strong and direct connection between an anomaly and the condition that it is meant to identify. The scientists behind the study agree that more research is needed to understand what these findings mean. Meanwhile, parents of newborns and infants are asked to continue to follow SIDS precautions. These include always placing a baby younger than 1 year old on its back for sleep, including for a nap, and keeping the sleep area free of loose blankets, sheets, pillows, bumper pads and soft toys.

Q: My internist has recommended a colonoscopy. I dread having it, though, because I'm concerned about the liquid laxative prep it requires. I suffer from IBS, which is often painful. Is it possible this prep will provoke a severe IBS occurrence, or might it make my condition worse?


A: You've asked a challenging question and, unfortunately, there is no clear-cut answer. To explain why, let's begin with some background.

Irritable bowel syndrome, or IBS, is a disorder that causes pain, discomfort and dysfunction in the large intestine. In addition to cramping, bloating, gas and abdominal pain, people with IBS experience ongoing episodes of diarrhea or constipation, and often both. There is no cure, which makes it a chronic condition.

Although the specific cause of the syndrome is not clear, recent research has linked it to certain changes that take place in the population of the gut microbiome. The vast majority of the microbiota that comprise the gut microbiome reside in the colon, which is also referred to as the large intestine. This is the portion of the gastrointestinal tract that is examined during a colonoscopy.

In order to perform an effective colonoscopy, the large intestine, which is where the body's solid waste collects, must be free of all debris. That's the only way for abnormalities to be visible. This necessitates the so-called colonoscopy prep, which entails a brief change of diet followed by the use of a laxative drink to completely void the bowel.

It's here the requirements of colonoscopy prep bump up against the challenges of IBS. While cleansing the bowel provides the clear field of vision needed to identify potential cancers, it also affects the intestinal flora. Studies show this process alters the numbers, diversity and stability of the populations of microbes living in the gut, and that it takes several weeks for the microbiome to recover. How this affects people with IBS, whose gut microbiome may already be out of balance, is not clear. Research is scarce, and people's experiences vary. Some say they are unaffected by the prep, and some experience a mild flare. Others report their symptoms of IBS go away altogether for several weeks after the bowel is cleansed.

Another thing to keep in mind is that colonoscopy prep has made great strides in recent years. The gallon of liquid once required is now often just two small bottles. There is evidence that splitting the dose, with half consumed the night before the procedure and half the morning of, is easier on the gut. Each colonoscopy center has its own protocols, and you can check for the one you are most comfortable with.

Your reluctance to undergo a colonoscopy due to the potential effects of the prep is understandable, but it's important to look at the big picture. The benefits of screening for colon cancer outweigh the risk of an IBS flare. A colonoscopy can identify precancerous polyps, which can be removed before they turn into cancer. When colorectal cancers are found early, they are highly treatable. And with normal results, you won't need another colonoscopy for 10 years.

• Dr. Eve Glazier is an internist and associate professor of medicine at UCLA Health. Dr. Elizabeth Ko is an internist and assistant professor of medicine at UCLA Health. Send your questions to

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