Hyperglycemia, nutrition and health outcomes in preterm infants

Abstract: BackgroundSurvival among very low birth weight (VLBW) and extremely preterm (EPT) infants has increased markedly during the last decades. Neonatal hyperglycemia is common in these infants and is known to be associated with adverse outcomes. However, much about neonatal hyperglycemia is still unknown: which mechanisms are responsible for it, its long-term risk profile, how to treat it and even how to define it. This thesis focuses on neonatal hyperglycemia in preterm-born infants - its prevalence, possible causes (including postnatal nutrition and its possible programming effect of later outcomes), consequences and treatment.MethodsTwo cohorts were studied in this thesis. The EXtremely PREterm infants in Sweden Study (EXPRESS) – a national population-based cohort - included all infants born before completed 27 gestational weeks during the years 2004-2007 in Sweden. Nutritional data as well as glucose measurements (n=9850) and insulin treatment data for the first 28 days of life were obtained for 580 infants. In a sub-cohort of 171 children, blood pressure measurements were obtained at a follow-up visit at 6.5 years of age. Neurodevelopment was assessed at 6.5 years of age in 436 children. Intellectual ability was assessed using Wechsler Intelligence Scale for Children IV (WISC-IV; n=355). Gross and fine motor function were assessed using Movement Assessment Battery for Children 2 (MABC-2; n=345).The very Low birth weight Infants - Glucose and Hormonal profiles over Time (LIGHT) study was a prospective cohort study that included 50 VLBW infants born in Umeå, Sweden, between 2016-2019. Infants were placed on continuous glucose monitoring (CGM) for a 48-hour period when a postmenstrual age (PMA) of 36 gestational weeks was reached (n=35).ResultsDaily prevalence of hyperglycemia > 10 mmol/L in EPT infants was high during the first two weeks of life (up to 30%), followed by a slow decrease thereafter. Protracted hyperglycemia > 8 mmol/L was detected in more than half of VLBW infants at PMA 36 weeks.In EPT infants, glucose concentrations during the first 28 days of life were increased by 1.6% on the day following an increase of 1 g/kg/day in parenteral carbohydrate intake. Male sex, amnionitis and prior hypoglycemia and hyperglycemia episodes were risk factors for hyperglycemia at PMA 36 weeks in VLBW infants.In EPT infants, neonatal hyperglycemia > 10 mmol/L was associated with increased 28-day mortality. Neonatal hyperglycemia, its severity and duration were associated with increased diastolic blood pressure (DBP) and lower MABC-2 scores at 6.5 years of age. Insulin treatment was associated with improved 28- and 70-day survival but not with BP or neurodevelopmental outcomes at 6.5 years of age.Higher protein intake during the first eight weeks of life was associated with higher DBP at 6.5 years of age. An increase of the carbohydrate intake by 1 g/kg/day during this period was associated with an increase of 0.18 SDS in systolic (SBP) and 0.14 SDS in DBP at 6.5 years. Growth during the same period was not associated with BP at 6.5 years.ConclusionsNeonatal hyperglycemia during the first four weeks of life was more common in EPT infants than has previously been described. Remaining glucose disturbances were common at PMA 36 weeks in VLBW infants. Parenteral glucose intakes within the range given seems to have had low contribution to glucose concentration variability. Neonatal hyperglycemia was associated with increased 28-day mortality as well as with increased blood pressure and reduced motor skills at 6.5 years of age. Carbohydrate intake in the immediate postnatal period was indepentently associated with increased blood pressure at 6.5 years of age. The results add to the knowledge regarding important risk factors and health effects of neonatal hyperglycemia. Different treatment options for neonatal hyperglycemia should be evaluated in animal models and in randomized controlled clinical trials in premature infants.