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Metabolic control during the neonatal period in phenylketonuria: associations with childhood IQ
Geertje B Liemburg1, Stephan C J Huijbregts2, Frank Rutsch3
1Division of Metabolic Diseases, Beatrix Children's Hospital, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
Insights
Early metabolic control in phenylketonuria (PKU) is crucial for cognitive development. Maintaining phenylalanine levels within the target range during the first month of life is linked to better IQ outcomes in later childhood.
Area of Science:
- Biochemistry
- Pediatrics
- Neuroscience
Background:
- Phenylketonuria (PKU) requires early intervention to manage phenylalanine levels.
- Neonatal metabolic control is a key factor in PKU management.
Purpose of the Study:
- To investigate the association between neonatal metabolic control indicators and later IQ in PKU patients.
- To determine if specific phenylalanine level metrics in the first month of life predict cognitive outcomes.
Main Methods:
- Correlated various phenylalanine level indicators (e.g., area under the curve, proportion above/below target) during the first month of life with IQ scores in 64 PKU patients.
- Patients' mean age was 10.8 years.
Main Results:
- Higher overall phenylalanine concentration and proportion of levels above 360 μmol/L in the first month were negatively correlated with later IQ.
- Phenylalanine levels during distinct neonatal periods (0-10, 11-20, 21-30 days) also showed negative correlations with IQ, with similar strengths.
Conclusions:
- Achieving target phenylalanine levels during the neonatal period is vital for long-term cognitive function in PKU.
- Neonatal metabolic control is more critical for later IQ than other assessed metabolic control indices.
Background:
In phenylketonuria, treatment and subsequent lowering of phenylalanine levels usually occur within the first month of life. This study investigated whether different indicators of metabolic control during the neonatal period were associated with IQ during late childhood/early adolescence.
Methods:
Overall phenylalanine concentration during the first month of life (total "area under the curve"), proportion of phenylalanine concentrations above upper target level (360 μmol/L) and proportion below lower target level (120 μmol/L) during this period, diagnostic phenylalanine levels, number of days until phenylalanine levels were <360 μmol/L, and lifetime and concurrent phenylalanine levels were correlated with IQ scores of 64 PKU patients (mean age 10.8 years, SD 2.9).
Results:
Overall phenylalanine concentration and proportion of phenylalanine concentrations >360 μmol/L during the first month of life negatively correlated with IQ in late childhood/early adolescence. Separately, phenylalanine concentrations during different periods within the first month of life (0-10 days, 11-20 days, 21-30 days) were negatively correlated with later IQ as well, but correlation strengths did not differ significantly. No further significant associations were found.
Conclusions:
In phenylketonuria, achievement of target-range phenylalanine levels during the neonatal period is important for cognition later in life, also when compared to other indicators of metabolic control.
Impact:
In phenylketonuria, it remains unclear during which age periods or developmental stages metabolic control is most important for later cognitive outcomes. Phenylalanine levels during the neonatal period were clearly and negatively related to later IQ, whereas no significant associations were observed for other indices of metabolic control. This emphasizes the relative importance of this period for cognitive development in phenylketonuria. No further distinctions were observed in strength of associations with later IQ between different indicators of metabolic control during the neonatal period. Thus, achievement of good metabolic control within 1 month after birth appears "safe" with respect to later cognitive outcomes.
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