How do socioeconomic inequalities and preterm birth interact to modify health and education outcomes? A narrative systematic review

Abstract

Objectives How are socioeconomic inequalities modified by, or how do they interact with, preterm birth?Design Narrative systematic review of quantitative observational studies of an interaction, or effect modification, between preterm birth and socioeconomic status.Data sources Five databases were searched for studies published between January 2000 and June 2020. Title and abstract were reviewed to identify articles for dual screening. All included studies were citation searched.Eligibility criteria Inclusion criteria were comparison across socioeconomic status and gestational age, interaction between the two, or stratification by either, and health or education as outcome.Data extraction and synthesis Data extracted included study design, sample size, outcome, interaction measure, effect and significance. Included studies were assessed for methodological quality and synthesised narratively.Results After searches, 52 studies were identified for full-text screening and, with supplementary citation searches, we identified 21 included studies. Eighteen studies studied interaction between gestational age or preterm birth, and socioeconomic status. Three groups of outcomes were identified: cognitive, mental health and developmental. Age at outcome measurement was divided into four categories: preschool, primary school (5–11), secondary school (11–18) and post school (18–29). Seven studies found a significant interaction between the effect of preterm birth and socioeconomic status. Six of these interactions demonstrate that the negative influence of low socioeconomic status was stronger for those born preterm (and vice versa) for cognitive and mental health outcomes, all in studies with a sample size of more than 100 000. One study found that negative effects of low socioeconomic status were reduced for those born preterm (and vice versa) for communication delay.Conclusions Our findings suggest that the impact of low socioeconomic status on cognitive and mental health outcomes is exacerbated by preterm birth. The remaining evidence suggests the effects are not modified; however, this is potentially due to underpowered studies. Public health action is indicated to support babies born preterm, particularly for disadvantaged families, to improve educational attainment and mental health.PROSPERO registration number CRD42020203613.