A heterogeneity analysis of health-related quality of life in early adults born very preterm or very low birthweight across the sociodemographic spectrum

Preterm birth and very low birthweight (VP/VLBW) are associated with poorer health-related quality of life (HRQoL) outcomes extending into adulthood, yet it remains unclear how these effects differ across sociodemographic subgroups. This study aimed to identify heterogeneity in the association of VP/VLBW on HRQoL in early adulthood, specifically examining maternal age, education, and ethnicity. Individual-level data from three longitudinal cohorts within the Research on European Children and Adults Born Preterm Consortium were analysed, including adults born VP (< 32 weeks' gestation) or VLBW (< 1500g), compared to term-born or normal birthweight controls. HRQoL was assessed using the Health Utilities Index Mark 3 (HUI3) at mean ages of 18-26 years. Bayesian Causal Forest and Shrinkage Bayesian Causal Forest methodologies were employed to estimate conditional average treatment effects. Results indicated significant heterogeneity in the effects of VP/VLBW birth on HRQoL by maternal age and education. Individuals born to mothers aged ≤25 years experienced the largest decrement in HUI3 scores (-0.08; 95 % CI -0.13, -0.02), compared to minimal or no decrements for individuals born to mothers aged ≥26 years. Similarly, lower maternal education was associated with larger decrements (-0.05; 95 % CI -0.09, -0.01), whereas high maternal education showed negligible impact (0.01; 95 % CI -0.04, 0.06). These findings highlight maternal sociodemographic characteristics as critical modifiers of VP/VLBW impacts on adult HRQoL, emphasizing the need for targeted health interventions for disadvantaged groups. Future research is warranted to examine whether modern neonatal care and changes in socioeconomic conditions can mitigate these HRQoL disparities across the life course.