Friday, November 13, 2009

Low birth weight doubles to triples the risk of stuttering!!


Per Alm and myself had some brain storming on this ground breaking large scale epidemiological article shedding important information on the underlying causes of stuttering:

Matern Child Health J. 2009 Nov 10.
Birth Weight and Health and Developmental Outcomes in US Children, 1997-2005.

Boulet SL, Schieve LA, Boyle CA.

National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, 1600 Clifton Road, MS-D02, Atlanta, GA, 30333, USA, sboulet@cdc.gov.

The primary goal of this study was to assess the association between the full birth weight distribution and prevalence of specific developmental disabilities and related measures of health and special education services utilization in US children. Using data from the 1997-2005 National Health Interview Survey (NHIS) Sample Child Core, we identified 87,578 children 3-17 years of age with parent-reported information on birth weight. We estimated the prevalences of DDs (attention-deficit/hyperactivity disorder [ADHD], autism, cerebral palsy, hearing impairment, learning disability without mental retardation, mental retardation, seizures, stuttering/stammering, and other developmental delay) and several indicators of health services utilization within a range of birth weight categories. We calculated odds ratios adjusted for demographic factors (AOR). We observed trends of decreasing disability/indicator prevalence with increasing birth weight up to a plateau. Although associations were strongest for very low birth weight, children with "normal" birth weights of 2,500-2,999 g were more likely than those with birth weights of 3,500-3,999 g to have mental retardation (AOR 1.9 [95% CI: 1.4-2.6]), cerebral palsy (AOR 2.4 [95% CI: 1.5-3.8]), learning disability without mental retardation (AOR 1.2 [95% CI: 1.1-1.4]), ADHD (AOR 1.2 [95% CI: 1.1-1.3]), and other developmental delay (AOR 1.3 [95% CI: 1.1-1.5]) and to receive special education services (AOR 1.3 [95% CI: 1.2-1.5]). While much research has focused on the health and developmental outcomes of low and very low birth weight children, these findings suggest that additional study of a continuous range of birth weights may be warranted.

Here are the conclusions of our debate. The statistical power of the study is very high due to the 88'000 children, and clearly correlates stuttering to birth weight. There is now clear empirical evidence that children in the lowest ranges of birth weight are twice to three times more likely to develop stuttering as compared to their normal-weight counterparts. Low birth weight is related to premature birth but also to various pregnancy problems. There can be a gene effect, but often it is environmental. (We are not completely sure about this split). It indicates abnormal neurobiological development of the brain and the body. Per will contact the authors to ask for a correlation matrix between the disorders, i.e. do some disorders occur at the same time. Per has written an article on a possible ADHD and stuttering connection. And Jelena Tadic has also talked about stuttering co-occuring with other disorders. The large study should more or less settle this open issue. Which disorders coincide with stuttering above random coincidence?

To summarize, low birth weight doubles to triples the risk of developing stuttering and confirms the suspicious that "stuttering" can start at the very least in these cases (but very likely in nearly all cases) years before the actual onset of overt stuttering!

18 comments:

Anonymous said...

what are the (other) risk factors for stuttering? Besides low birth weight....that has evidence?

So feed your kids?

Tom Weidig said...

Low birth weight rarely has to do with not feeding your kids, but more to do with pregnancy issues.

Norbert @ BSA said...

If stammering is a childhood developmental disorder then the connection with birth weight would not be surprising - children with low birth weight are susceptible to all kinds of developmental problems.

BTW, I was a 9 lbs baby....

Henk said...

Beside the neurobiological effects there is a (social) psychological effect too.

In such cases the parents are anxiously. When this remains for a long period the child feels the tension of them. Stress is a major factor of stuttering.

Kanstantsin said...

It would be interesting to calculate this correlation "low birth weight - stuttering" separately for kids who recovered from stuttering and who have not recovered (although it would be better to do this analyses with adult PWS). It might give some additional ideas about stutteing.
e.g. kids recovered from stuttering might have in average normal weight, and low birth rate might strongly correlate just with non-recovery from stuttering itself

MommaWriter said...

I've suspected that this correlation was there for a while now. My son, who stutters, was born prematurely (30weeks, . No one knows why that happened, but it was clearly something wrong with the way my body handles pregnancy, since the same thing happened with his sister (although she doesn't stutter). Obviously, that's a ridiculously small sample size, but when I reconnected with a friend from high school who stutters, I found out he was also born early. A friend of my son's, who was born at 32 weeks (not super early, but quite early nonetheless) also stutters a little, but not nearly as severely. It's true though that prematurity of any level can be associated with any number of developmental issues.

I'd beg to differ that stress had anything to do with my son developing a stutter. I'd say that we were vigilant about making sure he was developing well and the whole NICU experience is definitely anxiety-inducing, but I never felt like that was a big contributor. (How's that for scientific evidence?: )

Stacey

Anonymous said...

So you are speculating that babies with normal birth weight may have a greater chance of natural recovery?

Then what about the gender factor?

so stress during pregnancy may be a factor....which may lead to low birht weight or premature babies and lead to stuttering.

Anonymous said...

This is a brave question for Tom and other people with guts/intelligence:

The issue is: the measurement of stuttering, measurement of recovery, and the measurement of onset of stuttering is NOT good....

How do you determine when a child started stuttering and how do you determine when a child is no longer stuttering and recovered from stuttering with or without treatment???

There just seems to be so many gray areas in childhood stuttering

Tom Weidig said...

Norbert: " If stammering is a childhood developmental disorder then the connection with birth weight would not be surprising - children with low birth weight are susceptible to all kinds of developmental problems."

I think you have it the wrong way around. All kinds of developmental problems can lead to low birth weight. The low birth weight is just a proxy for underlying issues.

Henk: "Beside the neurobiological effects there is a (social) psychological effect too. In such cases the parents are anxiously. When this remains for a long period the child feels the tension of them. Stress is a major factor of stuttering."

There is no evidence for stress being a major factor. How does stress start stuttering? Explain me the mechanism. Moreover, why should these kids experience more stress? And any developmental issue can well have stress as a result, precisely because there is abnormal development.

Kanstantsin: "It would be interesting to calculate this correlation "low birth weight - stuttering" separately for kids who recovered from stuttering and who have not recovered (although it would be better to do this analyses with adult PWS). It might give some additional ideas about stutteing.
e.g. kids recovered from stuttering might have in average normal weight, and low birth rate might strongly correlate just with non-recovery from stuttering itself"

Excellent question. Per and I decided that Per will contact them for more information. My guess is that only those who do not recover have low birth weight because the others who recover just have an abnormal developmental schedule but there is nothing abnormal about their brain. Just a guess.

Tom Weidig said...

Ano: So you are speculating that babies with normal birth weight may have a greater chance of natural recovery? Then what about the gender factor? so stress during pregnancy may be a factor....which may lead to low birth weight or premature babies and lead to stuttering.

I would say yes. Not sure about gender. We need to keep in mind that low birth weight is just a proxy for underlying issues. It is not a causal factor as such.

Norbert @ BSA said...

What you are saying is low birth weight is just another developmental problem rather than a possible factor in developmental problems post-birth?

What about low-birth weight due to smoking? Or substance abuse? Or malnourishment of the mother?

Tom Weidig said...

No. I am saying that the body is developing according to a schedule triggered by genes and environmental events. For whatever reasons, this schedule is not working according to plan due to environmental impacts like food poisoning, physical trauma, smoking, high stress levels, chemicals, twin brother, or due to gene mutation.

One CONSEQUENCE of such an abnormal development is a low birth weight. For example, the child was born to early due to some brain/body issues: so the weight at 9 months would probably be OK, but it was born 2-3 months earlier and the baby does not get the best environment to grow. Or, maybe the child is not premature but could not gain more weight because the body doesn't work properly due to any issue, e.g. smoking or addiction of mother.

So the real issue is abnormal brain/body functioning which also leads to low birth weight and a brain structure leading to stuttering at the same time.

I do not believe that low birth weight is causal to stuttering and post-birth development. You can argue that low birth weight makes parents act differently but I don't buy this argument. If anything, they are more careful with the child and the child gets more attention from doctors.

MommaWriter said...

My personal opinion, based only on my experience and research into different preemie issues, is that premature birth alone can cause developmental problems. For instance, my son was 3 pounds 2 ounces (1446g) at birth. That was perfectly average for his gestation at 30 weeks, but it's still a pretty low birth weight. I don't think the premature delivery suggested he had developmental problems as much as it suggested that I had reproductive problems. That's not an uncommon problem, especially for women with issues such as incompetant cervix. In my case, my body apparently has a spontaneous "eject" button that comes on between 30-32 weeks into pregnancy (obviously not a clinical diagnosis!) There was no trauma, no known chemicals, no real stress, a perfectly normal pregnancy until it was suddenly over. I think the lingering developmental issues (which are relatively very minor) are truly due to being outside too soon.

The NICU environment puts all kinds of variables in play, including the risk of infection (through IVs, etc) that wasn't present in the womb in addition to all the external stimuli (bright lights, loud talking, ringing phones, monitor alarms, etc.) that the brain shouldn't yet have to process. And the lungs can be very underdeveloped when birth weight is low (my son was on a ventilator for 6 weeks while he had a systemic Candida infection and "putative meningitis"...which they never confirmed), so there's the potential for brain injury due to ischemia (lack of oxygen). And of course, there are the cases that Tom mentions where babies are born at low weights for their gestation, indicating potential developmental issues. I feel like those children are at even greater risk of developmental issues...although if their systems are somehow mature, despite their small size, I could be wrong on that one.

Another clue is that very low birth weight babies have a very high risk of cerebral palsy (CP). CP is a neuromuscular disorder due to brain injury. One could imagine that a relatively minor brain injury (not enough to cause CP) in just the right area could predispose a child to stuttering or other speech issues.

I know my son's brain did not develop entirely normally (he had an MRI when I was unnecessarily worried at how severe his stuttering had become). I chalk that up entirely to the prematurity...and the fact that he had a very long and rough NICU stay. Spend a few days in one of those units and it becomes clear how wrong it is for these tiny little babies to be growing in a noisy, bright environment as they are.

For what it's worth, my son is now 7. He has the sort of standard persistent stutter that comes and goes with no clear reason behind it. He's bright, he loves school and adores sports...both playing and watching. To date, his stuttering doesn't seem to concern him a whole lot. I'm aiming to keep it that way!

Oh, and I agree with you, Tom. I think we were more careful (perhaps overly careful) with our first chil because of the prematurity, but it did mean that his development was followed quite closely by doctors and other specialists for his first 3 years of life. Of course, they found no problems since he wasn't really speaking yet!

Stacey

Tom Weidig said...

>> premature birth alone can cause developmental problems.

I agree with you. And low birth weight can be a proxy for premature birth, simply because the baby had not had nine full months to grow. And premature birth might a much greater potential for developmental issues to occur due to the lack of the protective womb environement.

All kinds of stuff can happen that lead to low birth weight, but it always indicates (potential of) developmental issues.

Often, it is important to note that in most cases it will not impact speech but some other areas.

Re MRI scans, as you rightly pointed out scans are unnecessary, but tell that to a worried mother! ;-)

Not Whitey Bulger said...

Tom - great site!

I don’t know anything about premature babies, but I know a little about genetics. If you study genetics beyond introductory biology, you quickly learn that inheritance is generally far more complex than “I got it from my father.” There can be many genes that affect a trait in similar ways, interactions between multiple genes to produce a single trait, and interactions between genes and the environment required to produce a particular result. My (educated) speculation would be that stuttering can be produced in multiple ways genetically, and that in some cases an interaction between genes and environment - of some sort (or sorts) - could be required to trigger an underlying potential into a biological result. Add the complexity of the human brain, and it’s not surprising that low birth weight would correlate with increased incidence of stuttering outcomes. Or course, low birth weight hides a multitude of causes and effects, so these results really don’t tell us much,. A good first step working back from child to origin, but being trained in genetics, I’d rather work from genes forward. Needless to say, both approaches are needed.

Stuttering Stanley said...

Funny...I was born 2 1/2 months premature and weighed less than 2 pounds. They called me a "miracle" baby because I survived rapid pneumonia. I wonder if there is a connection?

Not Whitey Bulger said...

I was a fairly big baby, and went full term. Your personal case really doesn't say anything about causes - it's only when you look at a large sample that you learn anything, and even then, what you learn does not necessarily pertain to any one specific case.

Stuttering Stanley said...

Interesting. I have never heard about this risk factor. I, in fact, was born 2.5 months early and weighed less than three pounds at birth...and then dropped to less than 2 pounds due to rapid pneumonia. I was deemed a "miracle baby". And I've been very thin my whole life, you probably noticed this when we met in San Diego.