Mediating Factors in the Association of Maternal Educational Level With Pregnancy Outcomes: A Mendelian Randomization Study

Importance

Lower educational attainment is associated with increased risk of adverse pregnancy outcomes, but it is unclear which pathways mediate this association.

Objective

To investigate the association between educational attainment and pregnancy outcomes and the proportion of this association that is mediated through modifiable cardiometabolic risk factors.

Design, Setting, and Participants

In this 2-sample mendelian randomization (MR) cohort study, uncorrelated (R2 < 0.01) single-nucleotide variants (formerly single-nucleotide polymorphisms) associated with the exposure (P < 5 × 10-8) and mediators and genetic associations with the pregnancy outcomes from genome-wide association studies were extracted. All participants were of European ancestry and were largely from Finland, Iceland, the United Kingdom, or the US. The inverse variance-weighted method was used in the main analysis, and the weighted median, weighted mode, and MR Egger regression were used in sensitivity analyses. In mediation analyses, the direct effect of educational attainment estimated in multivariable MR was compared with the total effect estimated in the main univariable MR analysis. Data were extracted between December 1, 2022, and April 30, 2023.

Exposure

Genetically estimated educational attainment. The mediators considered were genetically estimated type 2 diabetes, body mass index, smoking, high-density lipoprotein cholesterol level, and systolic blood pressure.

Main Outcomes and Measures

Ectopic pregnancy, hyperemesis gravidarum, gestational diabetes, preeclampsia, preterm birth, and offspring birth weight.

Results

The analyses included 3 037 499 individuals with data on educational attainment, and those included in studies on pregnancy outcomes ranged from 141 014 for ectopic pregnancy to 270 002 with data on offspring birth weight. Each SD increase in genetically estimated educational attainment (ie, 3.4 years) was associated with an increased birth weight of 42 (95% CI, 28-56) g and an odds ratio ranging from 0.53 (95% CI, 0.46-0.60) for ectopic pregnancy to 0.81 (95% CI, 0.71-0.93) for preeclampsia. The combined proportion of the association that was mediated by the 5 cardiometabolic risk factors ranged from -17% (95% CI, -46% to 26%) for hyperemesis gravidarum to 78% (95% CI, 10%-208%) for preeclampsia. Sensitivity analyses accounting for pleiotropy were consistent with the main analyses.

Conclusions and Relevance

In this MR cohort study, intervening for type 2 diabetes, body mass index, smoking, high-density lipoprotein cholesterol level, and systolic blood pressure may lead to reductions in several adverse pregnancy outcomes associated with lower levels of education. Such public health interventions would serve to reduce health disparities attributable to social inequalities.

Direct and indirect effects of socioeconomic status on sepsis risk and mortality: a mediation analysis of the HUNT Study

BACKGROUND

Socioeconomic status (SES) may influence risk of sepsis and sepsis-related mortality, but to what extent lifestyle and health-related factors mediate this effect is not known.

METHODS

The study included 65 227 participants of the population-based HUNT Study in Norway linked with hospital records to identify incident sepsis and sepsis-related deaths. Cox regression estimated HRs of sepsis risk and mortality associated with different indicators of SES, whereas mediation analyses were based on an inverse odds weighting approach.

RESULTS

During ~23 years of follow-up (1.3 million person-years), 4200 sepsis cases and 1277 sepsis-related deaths occurred. Overall, participants with low SES had a consistently increased sepsis risk and sepsis-related mortality using education, occupational class and financial difficulties as indicators of SES. Smoking and alcohol consumption explained 57% of the sepsis risk related to low education, whereas adding risk factors of cardiovascular disease and chronic diseases to the model increased the explained proportion to 78% and 82%, respectively.

CONCLUSION

This study shows that SES is inversely associated with sepsis risk and mortality. Approximately 80% of the effect of education on sepsis risk was explained by modifiable lifestyle and health-related factors that could be targets for prevention.