Non-linear association between admission temperature and neonatal mortality in a low-resource setting

Abstract

Both neonatal hypothermia and hyperthermia represent important risk factors for neonatal mortality, but information on mortality risk across a full range of neonatal temperatures is lacking in low-resource settings. We evaluated the association between neonatal mortality and a full range of admission temperatures in a low-resource setting. This retrospective observational study was conducted at Beira Central Hospital, Mozambique. The relationship between admission temperature and mortality was evaluated using multivariable analyses with temperature modeled as non-linear term. Among 2098 neonates admitted to the Special Care Unit between January-December 2017, admission temperature was available in 1344 neonates (64%) who were included in the analysis. A non-linear association between mortality rate and temperature was identified. Mortality rate decreased from 84% at 32 °C to 64% at 34.6 °C (- 8% per °C), to 41% at 36 °C (- 16% per °C), to 26% to 36.6 °C (- 25% per °C) and to 22% at 38.3 °C (- 2% per °C), then increased to 40% at 41 °C (+ 7% per °C). Mortality rate was estimated to be at minimum at admission temperature of 37.5 °C. In conclusions, the non-linear relationship highlighted different mortality risks across a full range of neonatal temperatures in a low-resource setting. Admission temperature was not recorded in one third of neonates.

Figure 1

Number of neonates (A), boxplot of neonatal temperature (B) and birthplace (C) according to ranges of neonatal temperature at admission.

Figure 2

Observed mortality rate according to ranges of neonatal temperature at admission (A); estimated mortality rate according to neonatal temperature at admission as modeled with first order polynomial (B) or restricted cubic splines (C). Shaded areas represent bootstrap 95% confidence intervals.

Figure 3

Non-linear association between mortality rate and temperature in preterm (A) and term (B) infants. Shaded areas represent bootstrap 95% confidence intervals.

Figure 4

Nomograms for all patients. Diagnosis legend: fever, trauma, jaundice/hyperbilirubinemia, other (A); wet lung (B); asphyxia/HIE (C); sepsis/seizures (D); prematurity (E); congenital malformations (F). Neonatal temperature at admission is expressed in °C. Birthweight is expressed as 100 g.

Figure 5

Nomograms for inborn and outborn patients. Diagnosis legend: fever, trauma, jaundice/hyperbilirubinemia, other (A); wet lung (B); asphyxia/HIE (C); sepsis/seizures (D); prematurity (E); congenital malformations (F). Neonatal temperature at admission is expressed in °C. Birthweight is expressed as 100 g.