Wednesday, December 21, 2011

Sleepless Mom Increases Risk of Preterm Baby

For us to understand what this study actually communicates to us as the reader, it is helpful to know what scale they used for establishing sleep quality. They used the PSQI (Pittsburgh Sleep Quality Index) which was originally developed in 1989. It tries to cover the broad nature of what makes up sleep quality. It's designed to be able to be filled out by adolescents and above, and is made of 19 self-rated questions (15 scaled questions and 4 fill-in-the-blank). The 15 scaled questions are on a scale of 0 (no difficulty) 3 (severe difficulty) and the 4 fill-in-the-blank are answers to bedtime, wake time, time to fall asleep, how long do you sleep. There are also 5 "bonus" multiple choice questions for the bed partners to rate your sleep quality (keep you honest), which do NOT go into you final score. A number greater than 5 is suggestive of a sleep disturbance of significance. It takes about 5 or so minutes to fill out on average. So, in case YOU want to find out where you stand. I've included the PSQI here for you. 
By the way, this index is NOT designed just for pregnant women but for EVERYONE. This index is NOT designed to tell you WHY you have sleep disruption and DOES NOT predict anything about what an overnight sleep study would show except sleep onset latency (delay) and only sometimes at that.


Okay, so this Index is for ANYONE, but if you are a woman who is pregnant, plan to be pregnant, or have have pity for pregnant women, then this index and this study is applicable.

In it, they followed 166 pregnant women.
Average age was just over 28.
They used the above sleep quality scale to judge what the quality of their sleep was (but, again, not necessarily WHY their sleep wasn't great), and then decided if there was a link to them having preterm babies.
What's a preterm baby? A baby born after less than 37 weeks. So, as they note, preterm babies are on the rise in America. Over the last 25 years, the rate has increased by 3% (from 9 to 12% over that time). No one is sure exactly why it seems to be increasing.
So they looked at how well moms slept at 14-16 weeks, 24-26 weeks, and 30-32 weeks using this score and how that related to preterm baby risk.
If you can't sleep well during the first range (14-16 weeks) then you are 25% more likely to have a preterm baby than the mom who slept well.
If you can't sleep well during the third range (30-32 weeks) then you are 18% more likely to have a preterm baby, which is a more modest increase.
What about that middle 24-26 week range? Those mom's slept better and there was no significant increase in preterm risk, and it's well-established that moms just sleep better during that time anyway for some hormonal reason we don't really understand well enough yet.

WHY DOES THIS CAUSE A GREATER PRETERM RISK? Not sure. The working hypothesis that needs more testing is that the increase inflammatory mediators released by the stress of not sleeping well (or by the same stress that causes one not to sleep) induces a cascade leading an early delivery. 

What the study didn't questionaire for was such things as chronic pain/financial stress/life-event stress/relationship stress/post-traumatic stress disorders, etc. in enough numbers and ways to connect these things as a cause for poor sleep and therefore preterm delivery, although a future test may help make this connection more fully now that this current study sets a precendent for future studies involving more pregnant, sleepy women willing to fill out longer questionnaires. 


Mom's Poor Sleep Linked to Preterm Birth

Poor sleep quality, in both early and late pregnancy, may be associated with an increased risk of a preterm delivery, researchers said.

Poor sleep quality was a predictor of preterm birth in early pregnancy (14-16 weeks), and with every one-point increase on a sleep index scale, the odds of preterm birth increased 25%, reported Michele L. Okun, PhD, of the University of Pittsburgh, and colleagues in the November 1 issue of Sleep. The odds increased by 18% in later pregnancy, they said.

Although the specific pathways through which disturbed sleep contributes to preterm birth are unknown, it is possible that poor sleep may act independently or with other established risk factors, such as stress, they wrote.

The rate of preterm birth in the U.S. has increased from approximately 9% to 12% in the last 25 years. Poor sleep quality during pregnancy is related to adverse health outcomes.
Previous research has evaluated whether sleep quality during pregnancy is a clinically relevant risk factor for preeclampsia, longer labor, poor delivery outcomes, postpartum depression, and preterm birth. Although several risk factors have been identified, a gap in understanding the pathophysiology of preterm birth remains, the authors stated.
Okun's group evaluated the relationship between subjective sleep quality at 14-16, 24-26, and 30-32 weeks gestation and the risk of preterm delivery (<37 weeks). They hypothesized that poor sleep quality, especially in early pregnancy, is associated with an increased risk of delivering preterm.

In addition, the researchers explored the possibility that disrupted sleep might partially explain the established relationship between psychosocial stress and preterm birth.
Participants in the study included 166 pregnant women (mean age 28.6). Self-report questionnaires, including the Pittsburgh Sleep Quality Index, were used. Logistic regression models were used to evaluate whether sleep quality was linked to preterm delivery.
They found that poor sleep quality was a predictor of preterm birth, with the largest effects, a 25% increase, in early pregnancy at 14-16 weeks (OR 1.25, 95% CI 1.04-1.50, P=0.02).
More modest effects (18%) were found in later pregnancy at 30-32 weeks (OR, 1.18, CI 0.98-1.42, P=0.07).
Sleep quality in the second trimester did not correlate with increased risk and the authors suggested sleep often improves modestly during this part of pregnancy, although it was not unclear why. One explanation might be hormones or other biological pathways playing a role, but there are no data on that theory, they added.

However, the data from this study provide new evidence to support the hypothesis that disturbed sleep in early pregnancy may become a critical risk factor for adverse pregnancy outcomes.
Okun and her co-authors suggest a biological cause for this relationship: Poor sleep quality has been shown to initiate inflammation, possibly activating the processes associated with premature childbirth. Sleep disruption also might do this in combination with stress, a known activator of inflammation.
Other influences on impaired sleep included financial stress, stressful life events, and post-traumatic stress disorder.

Study limitations included the small size of the study and the inability to generalize to all women. Also, although sleep quality was the only measure of sleep available, additional measures, such as continuity and duration, are needed to provide supporting evidence, the researchers said. Further studies are need to test the relationship, they said.
What is unique in this study, Okun said, is that it may be possible to identify a risk early in the pregnancy, when there is time to intervene, possibly with modifications in behavior.