Almost one in 10 people worldwide are born preterm. It is known that premature birth is associated with a higher of risk of mortality in early childhood, but now Yale School of Public Health researchers and Norwegian colleagues have assessed the relationship between gestational age at birth and early adult mortality, and determined that there is a heightened risk.
The study examined the association between preterm gestational age at birth and all-cause and cause-specific mortality in young adulthood, specifically mortality from external causes, cardiovascular diseases and cancer.
Researchers at the Norwegian University of Science and Technology, the Yale School of Public Health and the University of Bergen tracked more than 1.5 million Norwegian men and women born over a 30-year period between the ages of 15 and 45. They found that individuals born before 34 weeks gestation had a 50 percent increased risk of death from all causes compared with adults whose births were at term. Two thirds of the deaths were from external causes, such as accidents, violence and suicide. The risk estimates were particularly high for external causes of death after the age of 35
The study results were validated in a subset of more than 29,000 siblings, one child born preterm and the other at term. This methodology controls for variation in many genetic and environmental factors. In the sibling cohort, a two-fold increased risk of death due to accidents and violence for gestational age of less than 34 weeks was found compared to term births. The corresponding result for suicide was similar.
“Large Scandinavian and Nordic population-wide data sets are ideal for this type of research,” said Dr. Michael B. Bracken, Yale School of Public Health professor emeritus, senior research scientist and one of the paper’s authors. “They will allow additional follow-up to address these questions as the cohort ages.”
The authors theorize that mental illness, psychopathology and factors related to cognitive skills and social well-being might explain the risk of death from external causes. These conditions have all been previously observed in adolescents born preterm, but further research is needed to see if these and other patterns of mortality continue to be observed in older adults who were born preterm.
Modern neonatal intensive care and improved obstetrical management such as prenatal maternal corticosteroids were introduced in the late 1960s and have considerably improved survival of preterm infants.
Previous Scandinavian data analyses have identified links between preterm birth and a wide range of educational, social, cognitive and mental health outcomes in adolescence and young adulthood. But as survivors of early neonatal intensive care are now reaching middle age, the latest research raises important questions about their risk for chronic disease and premature death, the researchers said.
The paper’s lead author, Dr. Kari Risnes, completed some of her doctoral work at the Yale Center for Perinatal Pediatric and Environmental Epidemiology under Bracken’s sponsorship. The research findings are published in the journal PLoS ONE.