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Aim The aim of this study was to determine the effects of early childhood stunting (height for age 2SD or more below reference values) and interventions on fine motor abilities at 11 to 12 years, and the relationship between fine motor abilities and school achievement and intelligence.
Method A cohort of stunted children who had participated in a randomized trial of psychosocial stimulation and/or nutritional supplementation in early childhood was compared with a group of non-stunted children. Fine motor abilities were assessed in 116 stunted (67 males, 49 females) and 80 non-stunted children (43 males, 37 females) at a mean age of 11 years 8 months (SD 4.3mo) and 11 years 9 months (SD 3.8mo) respectively. Testers were blind to the children’s group assignment.
Results Two fine motor factors were derived: rapid sequential continuous movements (RSCM) and dexterity. No effect of the early intervention was found. RSCM scores were lower in the stunted group than in the non-stunted group (p=0.01), but differences in dexterity were not significant (p=0.18) after adjusting for social background. Among stunted children, the RSCM score was significantly associated with IQ (p=0.04) and school achievement (all p<0.05).
Interpretation Stunting in early childhood is associated with poor scores on tests of rapid sequential continuous hand movements in later childhood. Children with poorer scores are at greater risk for low IQs and low levels of school achievement.
Moderate stunting (height for age 2SD or more below references values) is an indicator of chronic undernutrition and is estimated to affect 156 million children under 5 years of age in developing countries.1 Several studies have shown that children who are stunted in early childhood have poorer cognition, school achievement, and psychosocial function in later childhood.2,3
Animal research suggests that the cerebellum is particularly vulnerable to postnatal undernutrition4 owing to its relatively late development in neuro-ontogeny. The cerebellum is linked to motor coordination and fine adjustments to muscle tone.5 There is limited evidence that children’s fine motor ability is affected by undernutrition.6,7 In a study of Indian school-aged males, low weight for age was associated with poorer performance on motor tasks; out of the 16 males with the worst scores, 15 had abnormal electroencephalogram patterns, mostly in the frontal lobes.8 In another study, 10-year-old Indian children who were underweight and stunted in early childhood had deficits in timed coordinated tasks and balance,9 but not in dexterity.10 However, undernutrition is usually associated with poverty, and socio-economic status was not controlled for in these studies.
In 1986, we conducted a 2-year intervention trial of nutritional supplementation and psychosocial stimulation with stunted children aged 9 to 24 months. A group of non-stunted children were recruited for comparison. At enrolment, the stunted children had significantly lower developmental quotients and lower scores on all measured subscales (locomotor, hand and eye coordination, hearing and speech, and performance) of the Griffiths Scales of Mental Development11 than the non-stunted children, and the deficit increased over the 2 years. Stimulation significantly benefited the children’s developmental quotients and scores on each subscale, whereas supplementation benefited their growth, developmental quotients, and scores on the performance and locomotor subscales. In the group that received both interventions, the effects were additive and in this group scores were not significantly different from those of non-stunted children.12
At the first follow-up, at age 7 to 8 years, several tests were completed and two factors were derived from the scores: perceptual motor function and cognitive function. Stimulation had significant benefits on perceptual motor function, and supplementation had no benefit on either factor. The non-stunted group had significantly better scores on both factors than the stunted children who did not receive intervention.13
As previously reported,14 participants were reassessed at age 11 to 12 years; the groups receiving stimulation had significantly higher IQs on the Wechsler Intelligence Scales for Children – Revised and higher scores on the Raven’s Progressive Matrices and Peabody Picture Vocabulary Test than the control stunted group. There was no significant effect of supplementation on any test, and neither intervention benefited school achievement or behaviour. Compared with the non-stunted children, the stunted groups had significantly lower scores in IQ and school achievement, and more conduct problems were reported by their mothers.14,15
The aims of this study were (1) to examine children’s fine motor functions at age 11 to 12 years and determine whether early stimulation and supplementation has any effect on these, (2) to compare fine motor functions in stunted and non-stunted children, and (3) to examine the relationship between fine motor abilities and school achievement and intelligence.
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Neither stimulation nor supplementation resulted in long-term benefits on either of the fine motor factors in stunted children. The stunted groups had poorer performance on both the RSCM and dexterity factors than the non-stunted group. However, after controlling for age and social background, no difference remained in the dexterity factor. The stunting effect on the RSCM factor was small to moderate.
All tasks measured speed of execution and had good test–retest and interobserver reliability. Speed of performance is more reliable and stable over time than ratings of quality of movements.23 The eight fine motor tasks loaded onto two distinct factors – one requiring sequential or alternating continuous movements and the other requiring fine motor manipulation or dexterity. The factors related differently to social background. The dexterity factor was related to several social background and stimulation variables. In two dexterity tests, the tasks were related to writing and may depend on practice and socioeconomic background. The RSCM factor was not related to any of the measured social background variables. The motor tasks in the RSCM factor originated from a test of soft neurological signs,20 which are often unrelated to socio-economic status.24 Similar tests are used in the assessment of minor neurological dysfunction.25
The stimulation intervention included activities related to fine motor function, such as drawing and threading of beads, and the lack of benefit is surprising. Stimulation resulted in a significant improvement in hand–eye coordination immediately after intervention12 and in Grooved Pegboard scores at the 7-year follow-up.13 However, the lack of benefit from supplementation agrees with our findings at 7 years that supplementation results in no benefit on any test.
Our finding that RSCM performance is poorer in stunted children concurs with the findings of other studies that have used tasks from the Neurological Examination of Soft Signs,7–9 and we controlled more extensively for socioeconomic differences. One study also found differences in performance on Grooved Pegboard tests,6 but we are unaware of another study with undernourished children using similar pencil and paper tasks.
The findings suggest that nutritional insults in early childhood are associated with subtle changes in brain development in areas that control certain fine motor functions, and the effects are evident several years after the period of undernutrition. A recent study26 of functional magnetic resonance imaging in children with autism and typically developing children found that sequential oppositional finger tapping was related to activity in cortical and subcortical regions associated with motor execution, including the contralateral primary sensorimotor cortex, the contralateral thalamus, ipsilateral cerebellum, and supplementary motor area. The children with autism were slower at finger tapping and showed reduced activation in the ipsilateral anterior cerebellum, and greater activation in the supplementary motor area. It is possible that the stunted children also had changes in brain function in these areas. Why one factor was associated with undernutrition and not the other is unknown. We speculate that the factors are associated with activity in different areas of the brain and that one area may be more affected by undernutrition than another.
Poor fine motor function identified stunted children at risk of low IQ and poor school achievement, especially spelling and reading. Similar associations between fine motor ability and learning have been shown in other populations.24 Fine motor disability is a consistent predictor of school achievement,27 and academically at-risk children have a slower speed in finger opposition than those not at risk.28
A limitation of this study is that relatively few tests were used, and we were not able to carry out a full neurological examination. However, it is remarkable that the few tests used showed differences between nutritional groups and predicted intellectual and academic ability.