Maternal infection during pregnancy and autism: The flu hypothesis revisited.

By Nestor Lopez-Duran PhD

BRIEFS

The last issue of the Journal of Autism and Developmental Disorders included one of the largest examinations of the association between maternal infection during pregnancy and risk for autism. The study was conducted in the Denmark where researchers examined the maternal infection rates during pregnancy and autism diagnoses for all children born in Denmark between 1980 and 2005. ASD diagnosis was calculated by examining the Danish Psychiatric Central Registry, which includes information of all children who received outpatient or inpatient treatment with a diagnosis of ASD during those years. The researchers also examined the Danish National Hospital Registry, which includes information about all hospital admissions in the entire country during that time.

The researchers wanted to know whether children whose mothers had an infection during pregnancy were more likely than their peers to develop an autism spectrum disorder. In addition, they explored whether the nature of the infection (viral vs. bacterial), or the trimester during which the infection occurred, affected the risk of developing an ASD for the child.

The results:

  1. Overall, there was no relation between maternal infection during the entire pregnancy and ASD risk. However, there was a relation between infection at specific trimesters of the pregnancy and ASD risk:
  2. Viral infection during the 1st trimester of the pregnancy significantly increased the child’s risk of developing ASD. Specifically, children whose mother had a viral infection during the first trimester were about 200% more likely than their peers to develop an autism disorder.
  3. Bacterial infection during the 2nd trimester also increased the child’s risk of developing ASD but at a much smaller rate. Specifically, children whose mother had a bacterial infection during the second trimester were about 42% more likely than their peers to develop an ASD.

The authors indicated that this effect is likely due to exposure to the influenza virus. Specifically, in 50% of the children who had ASD and whose mothers had a viral infection during the first trimester, the virus was influenza.  Further, 4% of children whose mothers were admitted to the hospital during the first trimester due to the influenza virus developed autism. In contrast, only 0.6% of the children born during the period examined developed ASD. The rate of ASD among those whose mothers were admitted to the hospital during the first trimester due to the influenza virus was 6 times higher than in the general population.

Why is this the case? Researchers dont know for sure but a few theories have been proposed. One theory is that exposure of the fetus to the influenza virus increases the risk for developmental disorders. However, others believe that it is not the virus itself, but the maternal immune response to the virus that is harmful to the developing fetus.

UPDATE: Here is one additional piece of information that helps puts these findings into perspective. ONLY 1.5% of all ASD cases were children whose mother had infections during pregnancy. That is, even though infection during the 1st trimester significantly increased the risk of ASD, 98.5% of all ASD cases could be considered to be completely unrelated to maternal infection during pregnancy.

The reference: Atladóttir, H., Thorsen, P., Østergaard, L., Schendel, D., Lemcke, S., Abdallah, M., & Parner, E. (2010). Maternal Infection Requiring Hospitalization During Pregnancy and Autism Spectrum Disorders Journal of Autism and Developmental Disorders DOI: 10.1007/s10803-010-1006-y

Do Baby Einstein DVDs work? Exposing infants to educational dvds may affect their language development.

By Nestor Lopez-Duran PhD

A few weeks ago I wrote a study that showed that exposing premature babies to Mozart music may lead to metabolic changes that facilitate weight gain and better medical outcomes. That study is an example of one credible and positive outcome that came out of the “Mozart effect’ craze. Unfortunately, most of the other claims, such as that listening to Mozart improves intelligence, have been discredited. So today I’m discussing a similar fad: making babies watch educational dvds or movies. For example, an entire industry has been developed to provide ‘educational’ dvds designed for infants and toddlers, such as the Baby Einstein DVD series reduced and marketed by Walt Disney. These dvds are marketed as developmentally appropriate for young children and able to facilitate the development of various cognitive skills such as language. For example, the dvd Baby Wordsworth is supposed to help babies learn 30 English words using child-friendly scenes (e.g., puppets, etc).

But do they work?

The journal Archives of Pediatrics and Adolescent Medicine just published a study conducted by a team of researchers at the University of California at Riverside. The study included 95 babies/toddlers between the ages of 12 and 25 months. These children were randomly assigned to a Baby Wordsworth DVD condition or to a no DVD group. Parents of the children in the DVD group were asked to use the Baby Wordworth DVD as they would use any other media at home. The no DVD group simply completed a series of laboratory tasks but were not provided with a dvd to watch at home.  The study lasted for 6 weeks. Before and after the 6 weeks, the children went through a battery of tests and the parents completed a series of scales designed to measure the baby’s language and cognitive skills.

The results:

1.      By the end of the 6 weeks,  there was no difference between those infants who were repeatedly exposed to the dvd and those who were not exposed to the dvd in regards to their general language and cognitive abilities.

The above finding is not really surprising as it would be unrealistic to expect that the dvd would have a major impact on the childrens cognitive or language function in just 6 weeks. So a better question would be: Does the dvd help children learn those 30 words?

2.      By the end of the 6 weeks, those infants who watched the dvd during this time were not more likely than those who didn’t watch the DVD to say the words, recognize the words, or identify the words using pictures of the objects.

The findings suggest that the educational DVD does not facilitate the learning of these words by infants when exposed to the dvd in a naturalistic setting for 6 weeks. So far, I had not been surprised by these results, but I was a bit surprised by the following:

3.      Those infants exposed to the dvd at an earlier age (closer to 12 months) had lower overall language scores at the end of the 6 weeks than those exposed to the dvd at a later age (closer to 24 months) or those not exposed at all.

This seems to suggest that early exposure to the dvd can actually negatively impact language development. Although a couple of previous studies have found similar effects, this study is critical because it helps us answer one key question: does early exposure to the dvd affect language development or do children with language delays simply tend to watch more tv/dvds? For example, it is possible that parents of children who have more language delays buy the educational DVDs in order to help their children. If this is the case, there would be an association between watching dvds and language delays, but it would not be the DVD that contributed to the language delay. But this study suggests that this may not be the case because the participants in this study were randomly assigned to the DVD or the no DVD group. That is, in this study, the use of the DVD is unlikely to be due to parental concerns about the children’s language development.

So what can explain the possible detrimental effects of watching these educational dvds at an early age? The authors mentioned a couple of possibilities. It is possible that having the dvd as a tool kept the parents from engaging verbally with the infants leading to a delay in language development. It is also possible that the dvd lacks one major component of the language learning process: The Authors explain:


Regarding word learning specifically, a large body of language acquisition research suggests infants are more likely to learn words for novel objects if a speaker is looking at an object rather than attending elsewhere or looking directly at the child.18 Thus, learning words from a television screen requires children to be paying attention to the screen and also to be aware of the relevant referent object to which the on-screen labeler is referring. In the case of the DVD used in this study, the onscreen character looked directly at the children and signed the name for the object while a voice-over spoke the label. This scenario is very different from the optimal word learning scenario for children younger than 2 years.

Regardless of the reason, the results of this and previous studies seem to suggest that exposing young infants to television, even when such media was specifically designed as an educational tool for babies, may be associated with a delay in language development.
The reference: Richert, R., Robb, M., Fender, J., & Wartella, E. (2010). Word Learning From Baby Videos Archives of Pediatrics and Adolescent Medicine DOI: 10.1001/archpediatrics.2010.24

Mozart Effect: The effect of music on premature babies

By Nestor Lopez-Duran PhD

Do you remember the Mozart Effect? In the 1990s a small yet very influential study showed that listening to classical music, and in particular Mozart, improved test performance in college students -thus Mozart must make you smarter! The public reacted and an entire industry was born. Parents rushed to the stores to purchase Mozart CDs so they could play it to their unborn children (hopefully not Mozarts Requiem which, although is one of my favorite works of all time, it is bound to traumatize anyone under 14). Even the State of Georgia passed a law requiring the free distribution of CDs to new mothers! The Governor at the time was widely quoted saying:

As you know, the brain has two lobes. The studies show that music engages both hemispheres of the brain its creativity and emotion engage the right lobe, while rhythm and pitch engage the left. So people who receive musical exposure at a young age develop a bundle of nerves that connects those two halves*

*I should go on, but I must note that the only thing correct in the above quote is that music indeed engages both hemispheres of the brain.

Since then, the effect of Mozart on intelligence was discredited. In fact, a comprehensive meta-analysis (a statistical reviews of previous studies on the topic) concluded that listening to Mozart actually had no effect on intelligence.

Yet, something very positive came out of these studies. Soon after, a series of studies showed that Mozart improves performance in some people because of its calming effects. That is, listening to mozart reduces stress in many people, and for those who are anxious, such reduction in stress would lead to better performance (e.g., whether a test or a sporting event). Other studies also showed that playing Mozart to at risk infants (premature or those with severe medical complications) resulted in better medical outcomes, such as fewer hospitalization days and more rapid weight gain.  Yet, researchers have not been able to identify the actual mechanisms that explain why premature babies react this way to Mozart.

In the last issue of the journal Pediatrics, there was a very small yet fascinating study on the effects of Mozart on premature babies. A team in Tel Avid was interested in examining whether changes in metabolic efficiency could explain the better outcomes observed among premature babies exposed to Mozart. In the study, the authors examined 20 preterm infants with a mean gestational age at birth of 29 weeks (range 26-35) and who were otherwise medically stable. At the time of the study, the infants were at a chronological gestational age of 30 to 37 weeks.  The methodology involved a randomized cross-over design. This means all babies where tested in both conditions during 2 consecutive days at the same time of the day. Some babies listened to Mozart during day 1 and underwent the no music condition during day 2, while other babies experienced the no music condition during day 1 and listened to Mozart during day 2.

The results:

The authors found that within 10 minutes of the start of the music the infants experienced an average of a 10-13% reduction in their Resting Energy Expenditure (REE). REE is often considered a measure of the amount of calories required to function during a specific time period during resting conditions. How could this contribute to our understanding of the Mozart effect on premature babies? If a baby reduces his/her REE, the baby then requires LESS calories to function. Imagine for a second that you require 2000 calories to function during the day. If you eat a 2,000 calorie diet, you would theoretically maintain your weight. Now imagine that you reduce your REE so now you only require 1,500 calories to function, yet you continue to eat the 2,000 calories (I think we call this aging!). What would happen? A similar process may be at play with these infants. It is possible that exposing the infants to Mozart reduces their REE and this results in a higher ratio of consumed calories to calories used, and thus more rapid weight gain and better medical outcomes.

Although this is a very compelling study, the authors warned that more research is necessary with larger samples. Yet, these findings, combined to previous findings showing improved medical outcomes among at-risk infants exposed to music, makes you wonder whether neonatal intensive care units should consider music exposure as standard practice for at risk infants.

The Reference:

Lubetzky, R., Mimouni, F., Dollberg, S., Reifen, R., Ashbel, G., & Mandel, D. (2009). Effect of Music by Mozart on Energy Expenditure in Growing Preterm Infants PEDIATRICS, 125 (1) DOI: 10.1542/peds.2009-0990

Autism and premature babies: some possible explanatory variables.

By Nestor Lopez-Duran PhD

This past week, while supervising the neuropsychology rotation of our doctoral students, I asked a student to clarify on a report whether the birth weight of a patient was below or at expectation for his gestational age. I explained that in most cases, it is not whether the baby was born prematurely, but whether his weight was normal for the length of the pregnancy.  Sometimes, being premature itself is not a risk factor for specific neurodevelopmental disorders. What is important in predicting healthy development is whether the baby shows typical growth up to the day of the birth even when the birth day is significantly before the full term date.

In the latest issue of the journal of the American Academy of Pediatrics there is a new epidemiological examination of the association between prematurity and autism that highlights the point I was making to my students. There are a number of studies that have found a link between prematurity and autism, in that premature babies are at greater risk for developing autism than full term babies. However, other studies have failed to replicate such findings. What could explain such discrepancy? One possibility is that it is not about being premature that increases the risk for autism, but instead such increased risk is due to complications and other factors associated with prematurity. If these variables have not been controlled similarly across studies then you will find studies providing conflicting results due to unknown, or uncontrolled, characteristics of the sample.

In the study published in Pediatrics, a Swedish team of researchers examined a population sample of 1,216 individuals with a autism spectrum diagnosis and over 6,000 non affected peers. These groups were similar in sex distribution, age, and most importantly: birth hospital. This is key, because it theoretically eliminates the possibility that any differences found between the groups are due to differences in the health services received during birth.  The authors first compared the risk for autism spectrum disorders associated with prematurity, and then examined whether specific neonatal complication factors could explain the observed risk.

Main finding:

  1. Being born at or before 31 weeks of gestation doubled the risk for developing an autism disorder  when compared to full term infants.
  2. Being born between 32 and 36 weeks of gestation increased the risk for an autism disorder by 55%.

However:

After adjusting (controlling) for neonatal complications and related factors, being born prematurely even before 32 week gestation DID NOT increase the risk of developing autism. That is, prematurity itself was not associated with autism once we take into account specific complications that are common among premature infants.

So what are the neonatal factors associated with autism risk?

While controlling for all neonatal and related factors:

  1. Low weight for gestational age was a risk factor for autism. Specifically, being small for gestational age increased the risk for developing autism by 86%.
  2. Having congenital malformations increased the risk by 106%
  3. Having intra-cranial bleeding, edema, or seizures increased the risk by 206%
  4. Having Hypoglycemia increased the risk for ASD by 120%

The following neonatal factors were NOT associated with an increased risk for autism: Jaundice, respiratory distress, infections, head and neck injuries during delivery, apgar score, being a twin, or being large for gestational age.

The results are consistent with other findings suggesting that weight for gestational age and related complications are more informative when estimating the probability of future neurodevelopmental disorders than simply being premature. This may also help explain why many premature babies dont show any lasting effects, even when they are born severely premature (<32 weeks), while others have significant developmental complications  (autism, ADHD, learning disabilities) even when they are born only a few weeks premature.

Buchmayer, S., Johansson, S., Johansson, A., Hultman, C., Sparen, P., & Cnattingius, S. (2009). Can Association Between Preterm Birth and Autism be Explained by Maternal or Neonatal Morbidity? PEDIATRICS, 124 (5) DOI: 10.1542/peds.2008-3582

Maternal obesity during pregnancy increases risk for ADHD Symptoms

By Nestor Lopez-Duran PhD

Maternal obesity during pregnancy is not one of the usual suspects of risk factors for ADHD. Yet, it seems that there is some preliminary evidence associating maternal obesity and ADHD. The latest study showing this link was published in the last issue of the Journal of Child Psychology and Psychiatrist by Alina Rodriguez from the Uppsala University in Sweden and Imperial College in London.

  1. In this new study the author first presented 4 issues that remain unresolved from previous research linking maternal obesity and ADHD
  2. Since obesity is associated with distress, is it possible that it is the distress during pregnancy that increases the risk for ADHD rather than the obesity?
  3. It is possible that maternal obesity and child ADHD are simply related to a common genetic factor. In such a case, it would be the genetic factor, and not the obesity that increases the risk for ADHD
  4. Maternal obesity is associated with small birth weight due to fetal growth restrictions, and some studies have linked small birth size to ADHD, possibly through its effects on emotional regulation. Thus, is small birth size the possible link between maternal obesity and ADHD?
  5. Maternal obesity is also associated with childhood obesity. Is it possible then than the increased risk for ADHD is due to childhood obesity?

To begin to tackle these issues, the author examined a cohort of women who were pregnant in Sweden from 1999 to 2000. The cohort for this analysis included 1,714 mother-child dyads who were evaluated when the child was 5 years of age. The Body Mass Index of the mothers was obtained during pregnancy and divided into 4 groups: underweight (15–19.99), normal weight (20–24.99),  overweight (25–29.99), and obese (+30). ADHD symptoms and emotionality  at age 5 were assessed via a questionnaires completed by both mothers and teachers. A number of covariates (or potentially explanatory factors) were also measured including maternal stress during pregnancy (divorce, financial problems, etc), socio-economic   status, smoking, the childs own weight, and depression.

The results:

  1. 37% of the mothers were classified as either overweight or obese (28% overweight and 10% obese)
  2. Obese mothers were significantly more depressed than the mothers in any of the other weight categories
  3. Children of obese mothers had significantly more symptoms of inattention but not hyperactivity when these symptoms were reported by the teachers. Specifically, maternal obesity was associated with a 2-fold increase in risk of teacher-rated inattention symptoms when compared to the children of normal-weight mothers. This association remained stable after controlling for the possible explanatory factors.
  4. Maternal Obesity was also associated with an increased risk for negative emotion regulation difficulties as indicated by a teacher-reported emotionality questionnaire.
  5. Maternal Obesity was not associated with any symptom when the symptoms were reported by the mother.

A couple of things were surprising. First, the results of the teacher-reported inattention problems were strong, which was of note given that no association was found between obesity and hyperactivity. This discrepancy between inattention and hyperactivity actually points towards a clear link between obesity and adhd (at least inattentive type). That is, since obesity was associated with inattention but not hyperactivity, it is unlikely that the original findings reflected simply an association between obesity and more general behavioral problems in childhood. Instead, the link seems to be specific to one aspect of ADHD. Second, the lack of association between obesity and maternal reported symptoms continues a pattern of findings I have previously discussed (see  for example this article on the effects of multiple daycare arrangements) that suggests that there are some limitations in the nature of maternal reports of the child behavior. In my experience working on several large scale family-based longitudinal studies, fathers and teachers reports of kids behaviors tend to agree with each other, but these reports do not always agree with the mothers. It seems that mothers often see, or report, different behavioral tendencies in their children when compared to what teachers see (or report).

In sum, the study provides additional evidence linking maternal obesity to inattention problems in early childhood. This study expands previous findings by also showing that such a link can not be fully explained by a number of potential factors, such as maternal stress, depression, and socio-economic status. However, please also note that this study did not actually assessed for the presence of ADHD. That is, these kids did not undergo the comprehensive evaluation needed for an accurate diagnosis of ADHD. Instead, the study assessed ADHD-related symptoms as reported by teachers and parents. It would be interesting to see if obesity is associated with true ADHD diagnoses in this population.

The reference: Rodriguez, A. (2009). Maternal pre-pregnancy obesity and risk for inattention and negative emotionality in children Journal of Child Psychology and Psychiatry DOI: 10.1111/j.1469-7610.2009.02133.x

Long term effects of prematurity: A glass half full of girls.

By Nestor Lopez-Duran PhD

Back in June I commented on an article that examined the mechanisms behind the type of cognitive disabilities experienced by very preterm children. That study showed marked impairment among premature kids, which is consistent with a long line of research showing significantly increased risks for cognitive deficits among children born under 30-week gestation. However, most of these studies were conducted decades ago, before significant advances in treatment and intervention programs for premature infant. Thus this begs the question, do children born extremely premature in the 1990s and 2000s continue to show significant levels of cognitive impairment?

In the latest issue of Pediatrics, a British team of researchers presented a cohort study of 219 survivors of extreme prematurity. The authors examined the cognitive and clinical profile of these kids at age 6 and 11, and compared them to  a group of 153 typically developing peers. The children completed a series of neurocognitive tasks, including the Kaufman-Assessment Battery for Children, a full pediatric evaluation to assess for the presence of cerebral palsy, motor functioning, and sensory impairment.

The results:

  1. Mean composite cognitive functioning scores were significantly lower in the preterm kids compared to their peers  (score of 83.7  vs. 104.1). This effect did not appear to be explained by socio-economic status of the families.
  2. Among typically developing peers, there was no difference in cognitive functioning between boys and girls. However, among the preterm children, boys had significantly lower cognitive scores than girls (by 8 points).
  3. When categorizing the impairment into 4 levels (severe, moderate, mild, no impairment), serious impairment (severe or moderate) was observed in 40% of preterm kids but only 1.3% of their typically developing peers. A gender effect was also observed. Serious impairment was seen in 50% of preterm boys but only 31% of preterm girls.
  4. Cerebral palsy was also twice as common among boys (25%) than girls (11%).
  5. Finally, as you can see in the graphic below, the rates of disabilities from age 6 to 11 did not change much. However, there appears to be a slight decrease in the rate of severe disability with a comparable increase in the rate of moderate disability.

Rates of disability among preterm children

In sum, the rates of serious cognitive deficits among preterm children are around 50%, indicating that despite advances in care, prematurity continues to lead to significant cognitive impairment. However, the rates of impairment among girls were significantly lower than among boys. Although it seems surprising that boys were more susceptible to the effects of prematurity than girls, other studies have reported similar findings. In fact, premature boys have lower survival rates than girls, suggesting that differences in the sex differentiation process before birth (such as exposure to androgens) may place boys at higher risk. Are there any neonatal endocrinologists in house who could shed some light on why exposure to androgens before birth may lead to greater susceptibility to developmental insults?

The reference:

Johnson, S., Fawke, J., Hennessy, E., Rowell, V., Thomas, S., Wolke, D., & Marlow, N. (2009). Neurodevelopmental Disability Through 11 Years of Age in Children Born Before 26 Weeks of Gestation PEDIATRICS, 124 (2) DOI: 10.1542/peds.2008-3743

Fathers depression during pregnancy related to excessive infant crying

By Nestor Lopez-Duran PhD

Thank you everyone for your patience during the two-week break in child-Psych.  As some of you know, I just relocated from Pittsburgh to Michigan where I started my new research program while working as an Assistant Professor at the Department of Psychology of The University of Michigan. The transition is time consuming but Im finally all settled in the new town and Im almost fully operational. I hope that Ill be able to write several weekly updates to child-psych starting this week.

Last night I had a chance to start reading again and an article published in Pediatrics caught my attention. The article reported the findings of a study examining the link between fathers depression and infant excess crying or colic.  The study appears to continue a line of research that explores the often neglected role of fathers mental health on the childs development. For example, recently I commented on the effects of father-daughter bond on the quality of the daughters romantic relationships, and on a study examining the impact of fathers (not mothers) postpartum depression on the childs language development.

In this new study, the researchers were interested in examining factors that may be associated with excess infant crying. Specifically, although mother depression (pre and postpartum) has been associated with colic, little is known about the effects of father depression. This is of major importance since recent studies suggest that fathers get depressed during and after pregnancy at rates that are comparable to mothers. The study was part of the Generation R Study, a large population-based longitudinal of child development. The study included 7,654 children born between 2002 and 2006. The researchers evaluated maternal and paternal depression at 20 weeks of pregnancy. Crying behaviors were assessed via parental questionnaire at 2 months after delivery.

The results:

  1. Excessive infant crying, defined as more than 3 hours per day on more than 3 days per week, was observed in 110 kids, or 2.5% of the sample
  2. Maternal depression was not associated with infant crying; however
  3. Parental depression was significant associated with infant crying. Specifically, infants who showed excess crying were significantly more likely to have depressed fathers when compared to their peers.
  4. The effect of paternal depression was still noticeable even when controlling for maternal depression and other explanatory variables.

Previous research have been criticized because of  the practice of obtaining all information from the same source. For example, fathers are asked to report on their childs behavior and also on their own behavior. This often results in report bias so that the fathers reports on the childs behavior may not be accurate and instead may be affected by their own behavior. However, this particular study has some strengths that help reduced the potential for report bias. Specifically, the study was prospective. Thus, parents reported on their depression  during pregnancy and then reported on the childs crying months later. This helps reduce the chance that the parents reports on the childs crying was affected by their own emotional state at that time. In addition, the prospective nature of the study helps control for the effect of the child on the parent. That is, babies with significant colic are more likely to elicit stress on their parents possibly leading to depression. However, since this study showed that parental depression prior to the birth of the baby was associated with excessive crying, the childs distress could not be the cause of the parental depression (at least the depression experienced before birth). All in all, this study provides further evidence that fathers mental health during birth and early childhood have a significant impact on the babys development.

The reference: van den Berg, M., van der Ende, J., Crijnen, A., Jaddoe, V., Moll, H., Mackenbach, J., Hofman, A., Hengeveld, M., Tiemeier, H., & Verhulst, F. (2009). Paternal Depressive Symptoms During Pregnancy Are Related to Excessive Infant Crying PEDIATRICS, 124 (1) DOI: 10.1542/peds.2008-3100

France vs. USA: Fat babies, french fries, and what parents do about it.

By Nestor Lopez-Duran PhD

I was recently reading a facebook discussion that began when someone complained about relatively skinny people who call themselves fat. Stop calling yourself fat if you wear a size 4. Thats not fat, so stop it. The discussion when on, mostly about who has a claim to the fat title, but sometimes it touched on important issues of self-perception and cultural relativity. What may be overweight for you, may be totally acceptable and even attractive to someone else.

But where do these differences come from? Are they simply a reflection of our parents own views of food, and eating practices? Do they come from our more general cultural environment, either through media, peers, or even how our culture affects our parents and therefore ourselves?

I know you need a dozen studies to address all these issues, but a recent study published by the American Dietetic Association help us move this conversation forward. In the study, a multinational team of researchers from France and the USA, examined the feeding practices of American and French parents. Specifically, they wanted to explore whether a number of factors that have been associated with individual variations in parent-to-child feeding practices differ between the American and the French parents. This would allow us to examine what cultural vs. individual factors are associated with such practices.

The study included 72 French children (age 4 to 7) and their parents, as well as 68 American children (age 4 to 7) and their parents.  The researchers obtained the body weight and BMI of the parents, and the body weight and height of the children.

The parents completed a measure of eating behaviors:

  • restrained eating;
  • uncontrolled eating; and
  • emotional eating)

a measure of feeding practices:

  • monitoring childs food;
  • using food as a reward;
  • child control over feeding;
  • teaching about nutrition;
  • encouraging balance an variety;
  • restricting child food intake for weight reasons;
  • restricting child food intake for health reasons; and
  • modeling healthy eating habits.

Finally, the parents completed a perception of child body task, in which they were shown 7 silhouettes of children and were asked to select the figure that best resembles the childs current weight, and to select the figure that resembles the shape they would like for their child. This allowed the researchers to calculate whether the parents thought their kids were thinner or heavier than what they desired.

The Results:

Basic USA France Comparisons.

  1. Contrary to what some may have been expecting, there was no difference in the BMI between the French and the American children. Both groups had a BMI in the 16 range (skinny for adult norms but normative for children).
  2. The parents differed in their BMI with the American having a significantly higher BMI than the French parents (25.6 vs. 22.6).
  3. Regarding parental practices:
    • The french parents were more likely to monitor the childs eating and also more likely to use food restriction for weight control.
    • In contrast, the American parents were more likely to use emotional eating, use food as a reward, allow for child control, and teach about nutrition.
  4. Also surprising to me, the French parents were more likely than the Americans to report that they wanted their children to be thinner.

Predictors of parental behaviors:

  1. A desire for the child to be thinner was related to higher monitoring and higher restriction of feeding, and this phenomenon appears to be stronger in France.
  2. Parental concerns that their kids may be overweight (not simply a desire for the child to be thinner) was associated with food restriction for weight and health reasons in both countries.
  3. The parents own food restriction was associated with restriction on the childs food.

In sum, the US kids were not heavier than the french kids even though their parents were. This is very encouraging as it implies that weight differences do not begin to show until later, allowing for the possibility of implementing effective intervention programs to prevent obesity at the elementary and middle school level. Its interesting that french parents were more likely than the American parents to report that they wanted their kids to be thinner. I wonder if this plays a role in future weight. For example, it may be that this weight consciousness among french parents may help prevent obesity as the kids enter adolescence and young adulthood.

This also raises another much more complex issue how do we balance the line between our need as a society to prevent obesity and related negative health outcomes, with the equally important need to prevent eating disorders, body image distortions, and to promote body acceptance of healthy but not necessarily skinny body types?

Finally, I should address one caveat. The two samples differed significantly in parental education. 43% of the french parents had a graduate degree or more, that compared to only 18% of US parents. However, 68% of the US sample reported a college degree while only 33% of the French sample reported one. I think this simply reflects educational differences between the US and Europe about what it means to have a college vs. a graduate degree.

The reference: de Lauzon-Guillain, B., Musher-Eizenman, D., Leporc, E., Holub, S., & Charles, M. (2009). Parental Feeding Practices in the United States and in France: Relationships with Childs Characteristics and Parents Eating Behavior Journal of the American Dietetic Association, 109 (6), 1064-1069 DOI: 10.1016/j.jada.2009.03.008

Premature babies and later executive functioning: its not all about speed.

By Nestor Lopez-Duran PhD

Yesterday I discussed a study on the possible link between the length and weight of a baby at birth and later intellectual functioning. One of the major strengths of that study was that they examined variations in weight and height in babies born within the normal range in terms of size and gestational age (not premature).  Among premature babies, the research has consistently shown an increased risk for later deficits, including lower intellectual capacity, higher rates of ADHD, learning disabilities, and other conduct problems. Yet the nature, or underlying neurocognitive mechanisms behind these deficits are poorly understood.

Deficits in executive functioning has been examined as a possible source of impairment in premature children. However, executive functioning is a broad term that refers to a number of cognitive processes, such as working memory, cognitive control, planning and organizing, etc, and it is unknown which of these components of executive functioning is particularly affected in preterm children.

The Journal of Abnormal Child Psychology recently published a comprehensive study of executive functioning among children born very preterm (less than 30 weeks gestation). The study included 50 premature children (27 boys, 23 girls) born at a mean gestational age of 28 weeks (range 25 to 30). The study also included 50 comparison children born at a mean gestational age of 37.7 weeks.  All children were about 6 years of age at the time of the study. Both groups completed a comprehensive battery of executive functioning tests (the Go/NoGo test, the Shape School task, the day-night stroop task. a verbal fluency task, Digit span, and the Object Classification Task for children). The children also completed a full IQ test (the WPPSI-R)

The Results:

Before controlling for processing speed and IQ, the premature children had significantly lower performance on tasks examining: accuracy and efficiency of cognitive switching, accuracy and efficiency of inhibitory control, verbal fluency, working memory, and concept categorization.

After controlling for processing speed and IQ separately, most of the previously observed differences remained, indicating that these deficits are not due to speed of processing or overall IQ. The only exception was efficiency in cognitive shifting, which was not different between these kids after controlling for processing speed.

The data suggest that impairments in executive functioning may be one of the underlying mechanism that contribute to the type of challenges that these children experience throughout childhood. However, the authors also raised one very interesting point. It is possible that these results do not reflect a stable pattern of deficits, but instead reflect a developmental lag. That is, these very preterm babies may just be delayed in the development of executive functioning skills and may not show the same patterns of deficits later in life.

The Reference: Aarnoudse-Moens, C., Smidts, D., Oosterlaan, J., Duivenvoorden, H., & Weisglas-Kuperus, N. (2009). Executive Function in Very Preterm Children at Early School Age Journal of Abnormal Child Psychology DOI: 10.1007/s10802-009-9327-z

Big babies, big heads, big IQ, and thoughts on eugenics.

By Nestor Lopez-Duran PhD

I spent the weekend helping my sister work on her dissertation. She is at MIT studying the role of eugenics in urban planning and architectural design in South America. So most of my weekend was spent reading about how in the early to mid 1900s  scientists, physicians and public health scientists in particular, promoted the underlying idea that the way to improve our society was to promote desirable populations. In most instances, their actions were appalling by todays standards (such as determining desirable and non-desirable immigrants based on morphology), but often the line that separates old eugenic ideas and todays theories was much more difficult to see. Was their effort to isolate people with communicative diseases so that they dont contaminate the superior healthy population that much different than some of todays practices? Or for example, was the French Lamarckean version of eugenics, which believed that populations could be improved by manipulating the environment even in the presence of undesirable genetic traits, that much different than our current gene by environment interaction research?

The tone has definitely changed (no current mainstream scientist speaks in terms of improving particular populations over others -aka explicit racism), and the underlying intentions have also changed from promoting desirable populations to alleviating suffering and improving health among all. Yet, I cant help but to think back to the old french members of the Museo Social when I read about intelligence research. I am not in any way suggesting that the authors of the study Im about to describe promote eugenic principles. Instead, I bring this point simply to open the discussion about those difficult to spot lines between current science and the early twentieth century eugenic thoughts that drove most of medical research at the time.

So what am I talking about?

In the latest issue of Pediatrics a team from Universities in Singapore, Australia, Canada, and New Zealand, reported the findings of an epidemiological study on the association between birth size and later IQ. Birth weight has been associated with cognitive performance in that children who are born significantly underweight (such as premature kids) tend to have cognitive deficits (ranging from simply lower IQ to severe deficits) when compared to kids that are born within the normal birth size range. Less is known however, whether variations within this normative range, such as variations in weight, length, or head size, also affect the kids future intellectual capacity or cognitive performance.

The authors studied a cohort of 1979 Asian (Singapore) children who attended mainstream schools and were participating in a large longitudinal study of risk for Myopia. Birth data were abstracted from the kids medical charts. IQ was measured using the Ravens Progressive Matrices test when the kids were in 2nd to 5th grade. The Ravens is a test of non-verbal reasoning which has been used as a proxy for intelligence (more on this later).

The results:

  1. Greater body length, body weight, and head size were all significantly associated with increases in IQ scores.
  2. For every 1Kg (2.2lb)  increase in body weight, the model predicted a 2.19 increase in IQ score. For every 1cm increase in length the model predicted an increase of 0.37 points in IQ
  3. IQ was not associated with gestational age
  4. An analysis of a sub-sample of siblings showed that the taller (at birth) sibling had significantly higher IQs that the shorter sibling.

In sum, the data seem to suggest that prenatal factors affecting body weight likely impact brain developmental processes that are associated with later cognitive performance.

Sorry Im being highly introspective in this post, but as I type Im wondering why this article made me think about the eugenic issues I read this past weekend. Maybe Im also reacting to Richard Nissbett wonderful lecture at the American Psychological Society two weeks ago regarding the role of culture and environment on IQ.  So I will end this post early by simply addressing three issues: 1) Im confused about the distribution of scores on their IQ measure and the norms used to reach those scores. Either this was not a representative population sample, or the norms used were outdated leading to significantly higher IQ estimates than expected in the population. Please note that even the low birth weight and short siblings had higher IQs than expected in the general population. 2) It is not quite accurate that the Ravens is highly correlated with IQ. In fact, the authors used a citation of a study conducted in 1956 that used measures that have been obsolete for decades. Instead, most recent research with newer IQ scales show that the Ravens progressive matrices tap only at some aspects of IQ and their IQ estimates are not highly correlated with full IQ scores obtained from current full batteries. Finally,  IQ in early to middle childhood is highly fluid and not a strong predictor of later IQ. Thus, I would love to see the developmental trajectory of these kids and examine more applicable outcomes such as educational attainment, etc.

The reference: Broekman, B., Chan, Y., Chong, Y., Quek, S., Fung, D., Low, Y., Ooi, Y., Gluckman, P., Meaney, M., Wong, T., & Saw, S. (2009). The Influence of Birth Size on Intelligence in Healthy Children PEDIATRICS, 123 (6) DOI: 10.1542/peds.2008-3344