MedicalResearch.com Interview with:
Jane E. Harding, DPhil
The University of Auckland
Auckland, New Zealand
MedicalResearch.com: What is the background for this study?
Response: Neonatal hypoglycaemia – low blood sugars in newborns – affects up to one in six babies born. It involves a sustained dip in blood sugar levels following birth. Blood glucose is the only fuel for babies’ brains (adults have alternative, back-up sources). So, if left untreated, this condition can cause developmental brain damage and lowered education outcomes later in life.
In developed economies, as many as a third of babies born are at risk. Risk factors include being born smaller or larger than usual, preterm babies and babies whose mothers have any form of diabetes – this last a growing group, with the rising incidence of gestational (pregnancy-related) diabetes.
We wanted to systematically track a cohort of babies to see if hypoglycaemia in babies affects their long-term health and development. So we designed the CHYLD study – Children with Hypoglycaemia and their Later Development. We are following 614 New Zealand babies born at risk of low blood sugar levels (neonatal hypoglycemia) into childhood to see if the condition affects their later growth and development. Our team includes researchers from the Liggins Institute, the University of Auckland, Waikato Hospital, the University of Canterbury and the University of Waterloo.
Half of the babies in the study were diagnosed with, and treated for low blood sugars. Seventy percent received extra, continuous monitoring of their blood sugar levels, which detected in some babies low levels that were not diagnosed by the heel-prick tests.
MedicalResearch.com: What are the main findings?
Response: At two years there was no relationship between blood sugar levels and later brain development, but at age 4.5 years, it’s clear that the children who experienced low blood sugar levels were more likely to have specific difficulties.
Children who had experienced low blood sugar levels as newborns were two to three times more likely to have difficulties with executive function (skills for problem-solving, planning, memory and attention) and visual-motor co-ordination (skills for fine control of movement, and understanding what you see) at age 4.5 years than children who had normal blood sugar levels.
Overall, the lower the blood sugar levels, or the more often they dropped, the greater the impairment was. Strikingly, children who had experienced a drop in blood sugar that was not detected using routine blood sugar monitoring were four times more likely to have difficulties with these skills – the first time this has been shown.
There was no link with lowered intelligence as measured by IQ. (These 4.5 year findings were published in JAMA Pediatrics.)
MedicalResearch.com: What should readers take away from your report?
Response: We don’t know yet what these impairments mean for the child in practical terms, but executive function and visual motor integration are believed to be important for learning at school, particularly for maths and reading.
To investigate whether the impairments at 4.5 years translate to learning or behaviour difficulties at school, we are now beginning to follow up the children at age 9-10 years.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: Internationally, there is no agreed cut-off for safe versus unsafe levels of blood sugar in newborns, he says. The one most commonly used in New Zealand, and in the CHYLD study, is <2.6 mmol/L, but authorities from other countries have recommended cut-offs as low as 1.4 mmol/L and as high as 3.3 mmol/L.
If we find at age 9-10 these children are more likely to have reading and maths difficulties, then we may urgently need to rethink what the diagnostic threshold should be.
This will make the findings of another ongoing study she is leading, hPOD, all the more relevant. In hPOD, we’re looking at whether a dextrose gel treatment that we have shown to be effective for this condition, could be routinely given to all at-risk babies as a preventative, before they develop low blood sugars – and before any damage could be done.
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McKinlay CJD, Alsweiler JM, Anstice NS, Burakevych N, Chakraborty A, Chase JG, Gamble GD, Harris DL, Jacobs RJ, Jiang Y, Paudel N, San Diego RJ, Thompson B, Wouldes TA, Harding JE, for the Children With Hypoglycemia and Their Later Development (CHYLD) Study Team. Association of Neonatal Glycemia With Neurodevelopmental Outcomes at 4.5 Years. JAMA Pediatr. Published online August 07, 2017. doi:10.1001/jamapediatrics.2017.1579
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