Zylbersztejn A, et al. - Given that child mortality is almost twice as high in England compared with Sweden, researchers sought for the extent to which adverse birth characteristics and socioeconomic factors explain this difference. The unfavourable distribution of birth characteristics in England largely explains the excess child mortality in England compared with Sweden. Associations of socioeconomic factors with adverse birth characteristics and increased mortality after 1 month of age made them contribute to these differences. Policies for reducing child mortality in England should consider reducing adverse birth characteristics through improving the health of women before and during pregnancy and reducing socioeconomic disadvantage should be considered to have most impact.

Methods

• Nationally representative cohorts of singleton livebirths were developed between Jan 1, 2003, and Dec 31, 2012; researchers used the Hospital Episode Statistics in England, and the Swedish Medical Birth Register in Sweden, with longitudinal follow-up from linked hospital admissions and mortality records to develop these cohorts.
• Mortality was analyzed as the outcome, based on deaths from any cause at age 2–27 days, 28–364 days, and 1–4 years.
• Cox proportional hazard regression models were used to determine the hazard ratios (HRs) for England compared with Sweden in all three age groups.
• For birth characteristics (gestational age, birthweight, sex, and congenital anomalies), and for socioeconomic factors (maternal age and socioeconomic status), they adjusted the models.

Results

• In this study, the English cohort comprised 3,932,886 births and 11,392 deaths and the Swedish cohort comprised 1,013,360 births and 1,927 deaths.
• For England compared with Sweden, the unadjusted HRs were 1·66 (95% CI 1·53–1·81) at 2–27 days, 1·59 (1·47–1·71) at 28–364 days, and 1·27 (1·15–1·40) at 1–4 years.
• At 2–27 days, birth characteristics explained 77% of the excess risk of death in England and socioeconomic factors explained a further 3%.
• At 28–364 days, birth characteristics explained 68% of the excess risk of death in England and socioeconomic factors explained a further 11%.
• The adjusted HR did not indicate a marked difference between countries at 1–4 years.