1. Attention problems in 6-year-old boys and girls:
Differentiating the impacts of being born premature vs. Small for Gestational Age
James Hall
Oxford Department of Education & Warwick Department of Psychology
Oxford Department of Education FELL Seminar Series
Wednesday 10 November 2010

2. Contents Introduction Background to the study Design of the Analysis
Key perinatal risks to child development
Differentiating the impacts of key perinatal risks
Perinatal risks for attention problems:
differing neurological mechanisms
gender differences
MRI scans
Background to the study
Measures
Design of the Analysis
Structural Equation Model
Results
Conclusions
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3. Introduction Context: Objectives:
While both prematurity and Small for Gestational Age births are well known risks for later attention problems, distinguishing their impacts is complicated by mixed evidence concerning mechanisms of effect and by gender differences
Objectives:
To reliably differentiate the impacts of prematurity from Small for Gestational Age on age 6 attention problems
While considering:
Potential neurological mechanisms
Differences between boys and girls

4. Small (weight) for Gestational Age (SGA)
key perinatal risks to child development
At-Birth Developmental Risk:
Caused by:
As indicated by:
Low Birth Weight
Prematurity
Limited Gestational Age
Intrauterine Growth Restriction (IUGR)
Small (weight) for Gestational Age (SGA)

5. differentiating the impacts of key perinatal risks
Low Birth Wight (<2.5kg)
IUGR
Prematurity
Very Low Birth Wight (<1.5kg)
IUGR
Prematurity
Extremely Low Birth Wight (<1kg)
IUGR
Prematurity
For ‘low’ birth weight babies, IUGR and prematurity are proportional causal risk factors...
...But as birth weight decreases, so prematurity becomes an increasingly strong predictor...
...With researchers commonly treating very low birth weight as commensurate with very preterm births

6. Birthweight, Gestational Age, & IUGR
Common conflation of perinatal risk factors regardless of gestational age and/or birth weight:
Key:
Low Birth Weight (LBW)
Prematurity (PT)
Intrauterine Growth Restriction (IUGR; commonly measured via SGA)
Small (birth weight) for Gestational Age (SGA)
Birth weight
Gestational Age
Ex./Very Preterm:
Preterm:
Fullterm:
Ex./Very Low:
LBW, PT
LBW , PT, IUGR
LBW, IUGR
Low:
LBW, PT, IUGR
Normal:
PT only
No-risk

7. perinatal risks for attention problems: differing neurological mechanisms & gender differences
Differentiating prematurity from SGA is informed by research investigating underlying mechanisms and by mixed results concerning gender differences:
Underlying neurological mechanisms:
Gender differences:
SGA/Prematurity Similarities
IUGR and Prematurity:
Both are associated with limited growth in infancy
Including limitations to brain volume as reflected in head circumference (structure)
SGA/Prematurity Differences
Prematurity alone:
Limited cortical folding (structure) leading to neurocognitive impairments (function)
Gender Similarities
Gender consistent differences in ADHD children:
Same neurological structures implicated:
Decreased brain volume
Decreased volume of the cerebellar vermis
Gender Differences
Male preponderance in attention problems has prompted a bias of research aimed at boys:
Indicating roles played by damaged frontal lobe and damaged basal ganglia (structures)

8. Mri scans Prematurity and limitations to cortical folding:
Cortical Folding Patterns in Human Development and Disease. David C. Van Essen Washington University in St. Louis Structural and Diffusion MRI Course OHBM, San Francisco June, 2009

9. Mri scans Prematurity and limitations to brain size (volume)
3D brain model of a preterm infant born at 31 weeks
3D brain model of a fullterm infant born at 40 weeks

10. Delayed brain maturation in ADHD children
Shaw P, Rapoport J, Evans A, et al. Attention-deficit/hyperactivity disorder is characterized by delay in cortical maturation. Proc Natl Acad Sci USA 2007; E-pub 2007 Nov. 16.

11. Background to the study:
The Bavarian Longitudinal Study (BLS; see Wolke, Ratschinski, Ohrt, and Riegel, 1994)
Prospective longitudinal study begun in Bavaria
Here examining the attention problems of age 6 children
Participants:
1,437 children from birth to age 6 years with measures of attention problems at 6 years rated by both mothers and psychologists
Main Outcome:
Attention problems at 6 years as measured by:
Mother: Attention Problems subscale of the CBCL
Psychologists: Task Orientation subscale of the measure entitled “Testers’ Rating of Child Behavior”
Developed by the BLS and used to assess child behavior during completion of cognitive tests at age 6 years

12. Predictor Measures Perinatal Risks: Prematurity (n=563; 39.2%)
Birth prior to 37 weeks gestation and measured via :
1) Maternal records of last menstrual period
2) Serial ultrasounds during pregnancy
3) Dubowitz examination
Small for Gestational Age (n=359; 25%)
Child weighed less than 90% of all gestational age-equivalent Bavarian children born within initial BLS recruitment period ( )

13. Predictor Measures Potential Mediators:
Cognition (Griffiths Scales of Babies’ Abilities for 0-2 year olds):
Total developmental quotient based on:
Locomotion (GROSS motor: balance, co-ordinate, control)
Personal-social skills (visual recognition of mother, following moving people with eyes and holding a spoon etc)
Hearing-speech (startled by sounds, searching for sounds with eyes, vocalisation other than crying etc)
Hand-eye co-ordination (FINE motor: moving light with eyes etc)
Performance (clasping objects placed in hand etc)
Head Circumference (proxy measure for brain volume):
Four ordinal categories relative to the total BLS sample:
1= < 3% (n=47; 3.3%)
2= 3-9% (n=105; 7.3%)
3= 10-90% (n=754; 52.5%)
4= > 90% (n=105; 7.3%)

14. Design of the analysis
Girls with Age 6 attention problems rated by mothers
Boys with Age 6 attention problems rated by mothers
Girls with Age 6 attention problems rated by psychologists
Boys with Age 6 attention problems rated by psychologists

15. Age 6 years: Attention Problems Design of the analysis Age 20 months:
Perinatal Period:
Attention Problems
Head Circumference
Premature? (<37 wks)
Cognition (Griffiths scales of babies’ development)
SGA? (<90%)
+ Background Confounders

16. Structural Equation Model
Model repeated for psychologist ratings of attention problems
Simply switched the measure of age 6 attention problems

17. Results 3-Way ANOVAs: Correlations
Attention problems varied significantly according to:
Gender (boys = more)
Premature birth (preterms = more)
SGA birth (SGA born = more)
(NO significant 2- or 3-way interactions, main effects only)
Correlations
Gender-Specific, stronger in GIRLS:
SGA birth with age 20 month head circumference
(r=-0.30 compared to r=-0.21 for boys)
Premature birth with age 20 month cognition
(r=-0.35 compared to r=-0.28 for boys)

18. Results
Perinatal period:
Age 20 months:
Age 6 years:
Attention Problems
Cognition
Prematurity
Head Circumference
SGA
…However, these results were most strongly apparent only when examining the attention problems of age 6 year old girls as rated by their mothers…

19. mother-rated age 6 attention problems: Total indirect impacts of prematurity and sga via cognition and head circumference (Stand. Betas)

20. Psychologist-rated age 6 attention problems: Total indirect impacts of prematurity and sga via cognition and head circumference (Stand. Betas)

21. Age 20 month female cognition and head circumference: Impacts of prematurity vs. sga (Stand. Betas)

22. Conclusions Identifying predictors of age 6 attention problems:
Differences in attention problems that are commonly found for children born premature and/or SGA can be partially accounted for by interim reductions to age 20 months cognition and head circumference
Differentiating preterm from SGA:
Via such intermediate reductions we can differentiate the impacts of being born premature vs. SGA. Some evidence that:
Prematurity → cognition (function) → attention problems
SGA → head circumference (structure) → attention problems
However, female prematurity may be a particularly salient risk factor despite its rarer incidence:
Although significant levels of female attention problems are rare, they are also more strongly associated with prematurity and SGA than these are in boys
Long-term/persistent deficits though?