People Born Prematurely More Likely to Develop PAH Later in Life, Study Says

People who were born prematurely, especially in recent years, are more likely to develop pulmonary arterial hypertension (PAH) later in life, a study says.

The findings of the study, “Increased risk of pulmonary hypertension following premature birth,” were published in the journal BMC Pediatrics.

PAH is a rare, life-threatening disorder caused by a narrowing of the arteries in the lungs, leading to high blood pressure.

“[A]mong children and adults, [PAH] has been linked to premature birth, even after adjustments for known risk factors such as congenital heart disease and chronic lung disease (CLD),” the researchers said.

In the study, researchers set out to evaluate the contribution of several factors, including premature birth, to the development of PAH in recent years, when modern neonatal care was introduced into routine clinical practice.

The population-based study gathered data from children age 5 and up, and adults who were born between 1973 and 2010, from the Swedish Medical Birth Register.

Data from PAH patients born between 1973 and 1996 were retrieved from the Swedish Pulmonary Arterial Hypertension Registry (SPAHR), and for those born between 1993 and 2010 from the country’s National Registry for Congenital Heart Disease (SWEDCON).

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All patients whose records had been retrieved from SPAHR were diagnosed with PAH after right heart catheterization, while those whose records had been obtained from SWEDCON were diagnosed after either right heart catheterization or echocardiography.

Each PAH patient in the study was matched to six individuals from the general Swedish population who did not have the disease and had been born in the same year, at the same hospital — the control group. The study involved 128 PAH patients and 768 controls.

Statistical analyses were used to assess the risk of PAH based on premature birth, after normalization for potential confounding factors, including the presence of heart defects, chromosomal abnormalities, and CLD. These analyses were performed for time of birth, grouped into five-year intervals.

Results showed that the incidence of premature births was more than three times higher among PAH patients (21%) compared with individuals from the general population without the disease (6%).

Over the entire study period, premature birth was associated an increased risk of PAH, with individuals born prematurely being 4.48 times more likely to develop the disease later in life compared with those born full-term.

After normalization for potential confounding factors, maternal high blood pressure, the presence of heart defects, chromosomal abnormalities, persistent pulmonary hypertension in the newborn (PPHN), and being female, all were found to be independently associated with PAH.

Five-year interval risk analyses showed that individuals born prematurely in recent years — from 2000 onward — had an even higher chance of developing PAH later in life (17.08 times higher than controls).

“This difference can be explained by the greater survival rates due to advances in neonatal care. The risk of developing PAH for a child born premature during the 1970s and 1980s who reached adulthood must be regarded as less likely than today, mainly because many children did not survive the neonatal period during these years,” researchers stated.

Overall, the team concluded that the “study strengthens the hypothesis that exposure to premature birth increases the risk of PAH.”

“We speculate that the discontinuation of normal [blood vessel formation in the lungs] in premature birth has an adverse impact on the vascular development of the infant’s lungs and on future growth. This may induce stress on the [heart muscle], causing PAH to occur later in life as the individual is exposed to other factors that further impair heart function,” they said.