Risk of health conditions among adults who were born premature

By Dr. Ananya Mandal, MDOct 22 2019

Swedish researchers looked at the risk of having health conditions including high blood pressure, asthma, diabetes, heart disease or epilepsy among adults who had been born prematurely. The study titled, “Prevalence of Survival Without Major Comorbidities Among Adults Born Prematurely,” was published in the latest issue of the JAMA this month.

Premature neonate in a special incubator - Image Credit: Pushba / Shutterstock

The team of researchers led by Dr. Casey Crump, MD, PhD, from, Icahn School of Medicine at Mount Sinai, Departments of Family Medicine and Community Health and of Population Health Science and Policy wrote in their study that there is around a 10 percent prevalence of preterm births across the world with 9.6 percent in the United States and 5 to 9 percent in most European nations in 2014. They added, “Because of advances in neonatal and pediatric care, more than 95% of preterm infants in developed countries now survive into adulthood.” These adults however are at risk of different health conditions they wrote as per the evidence seen in several studies.

The authors of the study wrote that preterm birth “has been associated with cardiometabolic, respiratory, and neuropsychiatric disorders in adulthood.” These include diseases such as heart disease, high blood pressure, diabetes, lung diseases such as asthma and developmental disorders and epilepsy. They defined the concomitant diseases or comorbidities according to the Adolescent and Young Adult Health Outcomes and Patient Experience (AYA HOPE) Comorbidity Index. This includes diseases that may start during adolescence and may continue into young adulthood or later. These include the neuropsychiatric disorders. The Charlson Comorbidity Index (CCI) was also used. This includes diseases that are long term and chronic and may progress into adulthood and raise the likelihood of early death.

For this study the team of researchers looked at birth registry data in Sweden of more than 2.5 million people (total of 2,566,699 births) who were born between 1973 and 1997. Of these births, 149,065 were born preterm meaning they were born at gestational age 37 weeks or earlier (term pregnancy is 40 weeks).

They looked at survival and disease free lives up to the age of 43. According to pre term births, they divided the population into some categories as follows –

• extremely preterm (22-27 weeks)
• very preterm (28-33 weeks)
• late preterm (34-36 weeks)
• early term (37-38 weeks)
• full-term (39-41 weeks)

Of the study population 48.6 percent were females and 5.8 percent were born prematurely. Results revealed that of all the births 54.6 percent were alive without any major medical conditions between ages 18 and 43 years according to the AYA HOPE comorbidity list. This compared with 63 percent of the individuals between ages 18 and 43 who lived without any major disease condition and had been born at full term. Among those born pre term 22.3 percent of those born extremely preterm, 48.5 percent of those born very pre term, 54 percent of those born late preterm and 61.2 percent of those born early term were found to be alive between 18 and 43 years with no major diseases. Using the Charlson Comorbidity Index (CCI) there was 73.1 percent survival without illness among all preterm births and 81.8 percent disease-free survival among term births. The percentage of disease free survival was 32.5 percent among extremely preterm, 66.4 percent very preterm, 77.1 late preterm and 80.4 early term respectively.

The researchers wrote that in this large cohort study they reveal that “prevalences of this outcome were statistically significantly lower in those born at earlier gestational ages vs full-term,” speaking of chronic diseases. They added that the findings were same for both males and females and did not depend on maternal disease factors or complications at birth. Genetic and environmental factors also did not influence the association between preterm birth and disease. The authors explain, “To our knowledge, the present study provides the first population-based estimates of the prevalence of survival without major comorbidities in adults born prematurely. The relatively high prevalence of this outcome reflects not only the treatment advances that have occurred over the past 50 years but also the apparent resilience of preterm survivors in maintaining good health.”

Looking at the future course of action, the authors of the study wrote, “A life-course approach to health has been declared a major priority by the World Health Organization and will be essential for monitoring and promoting the health of preterm birth survivors across the lifespan.”

One of the limitations of the study was that participants were followed up for the age of 43 years. A longer term follow up could yield more information, the authors explained. Further not all diseases and detailed clinical information was not available to validate the comorbidities. The outpatient department data was available only since 2001 wrote the researchers from specialty clinics.

The team of researchers wrote in conclusion, “Among persons born preterm in Sweden between 1973 and 1997, the majority survived to early to mid-adulthood without major comorbidities. However, outcomes were worse for those born extremely preterm.”