P2.G128: Trends and Racial Disparities in HIE-Related Mortality in Newborns in the United States, 2007-2022

Background: Hypoxic ischemic encephalopathy (HIE)is a significant cause of morbidity. Despite the benefits of therapeutic hypothermia (TH), the mortality rate can be as high as 14%. Data on HIE-related mortality (HIE-IMR) are limited to cohort studies and randomized control trials and it's unknown if there have been changes in mortality related to HIE since the advent of therapeutic hypothermia. Further, racial/ethnic disparities exist in the infant mortality rates in the United States (US), but little is known about racial/ethnic differences in HIE-IMR.

Methods: This was a retrospective cross-sectional analysis of linked birth and infant death records data from the Centers for Disease Control’s Wide-ranging Online Data for Epidemiologic Research website from years 2007-2022. We evaluated all infant deaths up to 1 year of age with the cause of death as hypoxic-ischemic encephalopathy (ICD-10 code P91.6) and birth asphyxia (ICD-10 code P21). The outcomes of interest were the changes in HIE-IMR and racial differences between Non-Hispanic White (NHW) and Non-Hispanic Black (NHB) HIE-IMR over time. HIE-IMR was calculated as per 100,000 livebirths. Race was ascertained based on death certificate reporting. Racial differences were assessed by NHB-to-NHW HIE-IMR ratio. Linear regression was used for trend analysis. P-value < 0.05 was considered statistically significant.

Results: Out of 59,117,761 live births from 2007-2021, 5,634 infants died from HIE (9.5 per 100,000). Of these, 79.7% died in the neonatal period; 46.3% were male; 60.5% were born at ≥36 weeks gestation; 49.5% had a birthweight ≥2.5 kg. The overall HIE-related IMR increased from 8.2 to 10.9 per 100,000 (P < 0.001: R=0.88). The HIE-related IMR was higher in NHB than in NHW (14.1 vs 9.2, P< 0.001) and except for 2013, the mortality rate was higher in NHB than NHW. There was no significant change in the HIE-related IMR in NHB (13.6 to 14.1; P = 0.33). In contrast, the HIE-related IMR in NHW infants showed a significant increase from 8.5 to 10.1 (P < 0.001; R=0.82). The overall NHB-to-NHW HIE-related IMR ratio was 1.5 and there was no significant change during the study period. When limited to infants of ≥36 weeks gestation (potential candidates for TH), the HIE-IMR was similar in NHB and NHW (6.3 vs 6.1; P=0.39). The HIE-IMR increased significantly from 4.7 to 7.9 (P < 0.001) in NHB and from 5 to 7.2 (P < 0.001).

Conclusion: The overall HIE-IMR rate increased significantly during the study period. The overall HIE-IMR was higher in NHB than in NHW, which mirrors the overall disparity in IMR in the US. This disparity persisted during the study period. This examination of the impact of race on different health outcomes underscores the urgent need for public health practitioners and policy makers to address the drivers mediating these disparities and improve outcomes for all races.