New Lancet study on child mortality in England and Sweden

A new study by a team of researchers led by Farr Institute's Ania Zylbersztejn, compares child mortality in England and Sweden – two high-income countries with similar levels of economic development and universal healthcare – to understand factors driving higher rates of child mortality in England. 

Deaths in children under-5 years old occur one and half times more often in England than in Sweden, according to an inter-country comparison of child mortality including more than 3.9 million English births and 1 million Swedish births, published in The Lancet. The difference is largely due to children in England typically weighing less at birth, being born earlier, and having more birth anomalies (such as congenital heart defects) than in Sweden.

With the UK and Sweden having similar levels of economic development and universal healthcare, the authors say that Sweden’s lower mortality rates should be achievable within the UK. However, the UK’s more unequal wealth distribution leads to poorer maternal health during pregnancy, which in turn causes more babies to be born prematurely and with a low birthweight.

The authors say that public health interventions to help improve the health of mothers before and during pregnancy, as well as reducing socioeconomic disadvantage overall, will be important to improve the health of babies at birth and increase their survival.

“While child deaths are still rare, the UK has one of the highest child mortality rates in western Europe,” says lead author Dr Ania Zylbersztejn, UCL Great Ormond Street Institute of Child Health, UK. “Babies born prematurely or with low birth weight have an increased risk of early death, and those who survive are more likely to have chronic ill health or disability. Families need to be better supported before and during pregnancy to improve maternal health, and in turn to give all children a healthy start in life.”

The study used routinely collected medical data from the English NHS and Swedish health services to compare births from 2003 to 2012, and track the children’s health and death records up to their fifth birthday. These records included information on the mother’s age, family’s socioeconomic position, as well as length of pregnancy, the child’s birthweight, gender, and whether they had any birth anomalies.

Overall, the study included more than 3.9 million English births, including 11392 deaths, and more than 1 million Swedish births and 1927 deaths.

Between the ages of two days to four years old, the child mortality rate for England was one and a half times higher than for Sweden (29 deaths per 10000 children in England, vs 19 deaths per 100000 children in Sweden). If the child mortality rate was the same in England as in Sweden 607 fewer child deaths per year would have occurred in England, equivalent to 6073 fewer child deaths in total from 2003-2012. These differences were mainly driven by differences in mortality among children aged under-1 year old.

The higher frequency of adverse birth characteristics such as low birth weight, preterm birth or congenital anomalies in England largely explained the excess risk of death compared to Sweden (accounting for 77% of the excess risk for newborns, 68% for under-1 year olds). Socioeconomic factors also contributed to the differences between the two countries (explaining a further 3% of excess risk in newborns, and further 11% in under-1 year olds). Combined, these factors fully explained the difference in survival for 1-4 year olds in England and Sweden.

Good maternal health (including maintaining a healthy weight, avoiding chronic illnesses such as diabetes, high blood pressure, psychological stress and infections) and health behaviours (such as a healthy diet, avoiding smoking, drugs and alcohol during pregnancy) are associated with healthy fetal development during pregnancy. However, many adverse maternal characteristics are more common in England than in Sweden.

The UK also has one of the most unequal distributions of wealth of all western countries. In 2003-2005, the most deprived 20% of the UK’s population had a seven-fold lower income than the least deprived 20%, while the gap in Sweden was only four-times. This suggests that many more people in England are socioeconomically disadvantaged, which is associated with preterm birth, low birthweight, birth anomalies and poor maternal health, reflecting circumstances and behaviours that are linked to poverty and stress.

To counter these issues, the authors propose creating population-wide programmes to help improve health and the socioeconomic circumstances of women before and during pregnancy. These may also have additional benefits, such as improving the lifelong health of future generations by reducing the impacts of adverse birth characteristics.

Co-author of the study, Professor Anders Hjern, Karolinska Institute, Sweden, says: “This study shows that the main explanations for the differences in child mortality rates between England and Sweden are systemic, and beyond the reach of healthcare services alone. The key factors here are likely to include Sweden’s broader welfare programs that have provided families with an economic safety net for over 50 years, the free and accessible educational system, including early child care, and public health policies for many lifestyle issues such as obesity, smoking and alcohol use.” 

The authors note some limitations, including that the quality of data in England was poorer than in Sweden, meaning that the study was restricted to 64.5% of English births between 2003-2012, compared to 99.8% of all Swedish births. The study included deaths from the second day of life to avoid including stillbirths that might be labelled as early infant deaths in either of the countries. Excluding deaths before two days old could underestimate the contribution of adverse birth characteristics to differences in child mortality between the two countries.

The two databases did not have comparable measures of socioeconomic status, and so the gap in deaths between children born to rich and poor families could not be compared between England and Sweden.

Writing in a linked Comment, Dr Marni Brownell, University of Manitoba, Canada, says: “… although the authors report that prenatal factors have a larger role in child mortality than socioeconomic factors present after birth, the results do not discount the important influence of social factors. The authors point to the extensive literature connecting adverse birth characteristics to socioeconomic factors, highlighting the importance of efforts to reduce poverty. Poverty reduction strategies for women during the prenatal period have shown great promise in reducing adverse birth characteristics6 and increasing maternal health-care-seeking behaviours during pregnancy.”

Zylbersztejn A, Gilbert R, Hjern A, Wijlaars L, Hardelid P. Child mortality in England compared with Sweden: a birth cohort study. Lancet 2018 (published online May 3). http://dx.doi.org/10.1016/S0140-6736(18)30670-6