Study awakens interest in pregnancy-diabetes links

The CU trial explores an often-overlooked culprit: disruptions to breathing during sleep
October 11th, 2017

In the third trimester of her recent pregnancy, Shari Hirsch took on some new responsibilities for herself and her unborn baby.

She had plenty to do already, caring with husband Eric for their 4-year-old son Jaxson in their Littleton home. But for several days, Hirsch, 28, agreed to take on some extra duties. For example, she stuck to a carefully balanced diet in the form of three daily meals prepared by the Clinical and Translational Research Center kitchen in the Leprino Building at UCHealth University of Colorado Hospital. For three nights, she put a probe on her finger, attached it to a watch-like device, and taped a microphone to her neck.

Hirsch does not have diabetes, but she also voluntarily wore a continuous glucose monitor, which delivered regular readings of her blood sugar levels. She had a series of blood draws and had her saliva and stool collected.

If it all sounds like a bit much for a mom-to-be to take on, Hirsch has no complaints, although she did allow that “the food was incredibly bland.” She handled that with her own seasonings. As for the bedtime device, “It was a little awkward having something attached to me, but I had no problem sleeping.”

Shari Hirsch with husband Eric, son Jaxson and newborn daughter Brielle. Hirsch’s participation in CU’s Sleep in Pregnancy study could help to shed light on the possible connections between sleep-disrupted breathing and gestational diabetes.

Diabetes wake-up call

Why all the extra effort? Hirsch is part of an ongoing study developed by Sarah Farabi, PhD, RN, a post-doctoral fellow with the University of Colorado School of Medicine’s Division of Endocrinology, Diabetes and Metabolism. Farabi is investigating links between a widespread but frequently overlooked problem, sleep-disordered breathing – think snoring and gasping for air – and short-term increases in blood sugar levels as well as insulin resistance.

“Sleep affects not just how good we feel but also our metabolism,” Farabi said. “We’ve recognized how important a mom’s health is to her baby. We know, for example, that smoking during pregnancy has an impact on the baby’s growth. We’re looking in this study at sleep [disruption] as another potential factor.”

Farabi’s study focuses on women classified as overweight or obese – those with a body mass index of 30 or greater – for two important reasons. First, they are more vulnerable to sleep disorders like obstructive sleep apnea, she noted. Second, the Centers for Disease Control and Prevention estimates that roughly half of all women in the United States are overweight or obese before they become pregnant. That means Farabi’s study subjects aren’t part of a niche but rather that they reflect a societal reality – and that they are quite possibly part of an increasingly common cycle linking obesity, sleep apnea, diabetes and other ailments that stem from them.

Regardless of weight, there are clues to the link between breathing disruptions during sleep and blood sugar spikes, said Teri Hernandez, PhD, RN, an associate professor with the Division of Endocrinology, Diabetes and Metabolism, who is Farabi’s mentor for the study. “Frequent awakenings” from interrupted breathing during sleep cause oxygen levels to drop and trigger a stress response – the release of adrenaline – which in turn increases blood glucose, Hernandez said.

Of course, it’s not clear when a pregnant woman who suffers through nights of fitful, interrupted sleep crosses the line from heightened glucose levels to gestational diabetes, Hernandez said. But there is also no doubt about the ripple effects of those that do. Mothers who develop gestational diabetes are up to 60 percent more likely to suffer later from Type 2 diabetes, Farabi said. The problem may cascade farther: the National Institute of Diabetes and Digestive and Kidney Diseases warns that the children of mothers with gestational diabetes could be at increased risk for obesity and Type 2 diabetes.

Wait until dark

It’s very important to diagnose gestational diabetes during the pregnancy because women can manage it with nutrition and medication like insulin, Hernandez noted. However, there are many women who pass the test for gestational diabetes but still have altered patterns of glucose regulation, perhaps because a woman’s sleep problems may go unrecognized or be written off as temporary or to be expected during the often physically uncomfortable months of pregnancy.

The WatchPAT device that is used in the Sleep in Pregnancy study. The index-finger probe records blood oxygen levels and other measurements, and runs to the wrist device which stores the data.

“In obese women without a diagnosis of gestational diabetes, we will often miss the sleep diagnosis if we don’t have heightened surveillance of their sleep patterns,” Hernandez said.

On a recent morning, Farabi spread on a table the surveillance tools she uses to study the sleep patterns of pregnant study participants like Shari Hirsch. With them, she aims to shed light on what’s going on in a woman’s body as she lies in the dark.

The pieces form an FDA-approved device called the WatchPAT from Israel-based Itamar Medical Ltd. A small probe covered by a blue cap fits over the index finger, measuring oxygen levels, heart rate, arterial pressure and other physiologic indicators during sleep. A cord attaches the probe to a device with an LED screen, strapped to the wrist, that records and saves the data. In addition, the patient fixes a small sensor with a microphone at the top of the chest to capture snoring and other sounds, as well as changes in body position.

The study participants wear the WatchPAT for three nights. It calculates a patient’s Apnea/Hypopnea Index (AHI), as well as her oxygen saturation levels, both key indicators of how severely her sleep was disrupted. Farabi sends women with high AHI scores to their physicians. Participants also get an oral glucose tolerance test, an indicator for insulin resistance, and a series of fasting blood draws.

These data, along with blood sugar levels recorded by the patient’s continuous glucose monitor – a sensor placed under the skin that is attached to a transmitter that wirelessly sends measurements to a small display device – form the body of evidence Farabi needs to solidify the link between sleep disruptions and spiking blood sugar levels. That could, in turn, help clinicians in the future stave off or at least reduce the risk of gestational diabetes in their patients.

With data from this relatively small pilot study, which is recruiting patients from UCH and other hospitals and clinics along the Front Range, Farabi hopes to secure a long-term National Institutes of Health grant to look at designing interventions for pregnant women with sleep-disrupted breathing and whether breaking the cycle can improve obstetrical outcomes.

Digging for data

The future is in the hands of women like Shari Hirsch, who volunteer to advance the research. After following her carefully controlled and balanced diet – a study detail included to avoid the possibility of the findings being confounded by food choices – wearing her WatchPAT and having her tests, Hirsch was happy to find that her blood sugar levels were normal and she did not suffer from sleep apnea. On Aug. 24, she gave birth to a healthy daughter, Brielle, after a C-section.

Sarah Farabi, who leads the Sleep in Pregnancy study, shows the WatchPAT sensor study participants wear at bedtime. It is secured at the top of the sternum. A microphone records snoring and other signs of sleep disruption.

But Shari and Brielle had one more commitment to meet for the study. Two weeks after the delivery, they headed to Children’s Hospital Colorado for a test to measure Brielle’s body composition, which can indicate a higher than normal percentage of fat. It’s a concern for children born to overweight mothers; Shari says she weighs about 35 pounds more than she should.

Brielle spent about two minutes in a small unit called a Pea Pod. The device analyzed Brielle’s body fat through air displacement while recording her length and weight, all the while soothing her with white noise.

In mid-September, Brielle weighed 7 pounds – about average, Shari said – and possessed a healthy appetite. “She’s a chow hound.”

Grateful for her and Brielle’s health, Shari said she hopes her participation helps Farabi find ways to protect other women.

“I was glad to have a chance to be part of the study and that they could use something from me to do research and learn about my baby,” she said. “It opened my eyes to how important controlling blood sugar is and how it affects the baby.”

For more information about the study, contact Sarah Farabi at sarah.farabi@ucdenver.edu.

About the author

Tyler Smith is a freelance writer based in metro Denver.