Atrial fibrillation risk has been linked to preterm birth and foetal growth, according to research from Sweden's Karolinska Institute.

According to the study, having a preterm or large-for-gestational-age birth increases the chance of developing atrial fibrillation in later life. The study was published in JAMA Paediatrics. Up to the age of 18, being small for gestational age at birth was solely linked to a higher risk of atrial fibrillation.

Over the past few decades, atrial fibrillation in young people has surged from previously low levels. "Atrial fibrillation at a young age may involve a heavy socioeconomic burden for the affected individuals and we need to learn more about the underlying causes of the disease," said the paper's first author Fen Yang, doctoral student at the Department of Global Health, Karolinska Institute.

"Our findings may highlight the need to monitor and prevent the disease in individuals with an elevated risk of atrial fibrillation."

The National Board of Health and Welfare estimates that 5% of Swedish births are preterm, or occurring before week 37. According to earlier research, people who are born prematurely or with foetal growth restriction have a marginally increased risk of later developing cardiovascular conditions like ischemic heart disease, stroke, and heart failure.

To date there have been little or mixed findings regarding the risk of atrial fibrillation in those with adverse birth outcomes. Atrial fibrillation increases the risk of stroke and other cardiovascular conditions, and is the most common form of cardiac arrhythmia.

It mainly affects the middle-aged and the elderly. The estimated incidence in the young is low, 0.12 to 0.16 percent. A collaborative study involving researchers from Karolinska Institute has now investigated the risk of atrial fibrillation according to preterm birth and foetal growth.

"We found that individuals born preterm and those who were large for gestational age at birth had a slightly higher risk of developing atrial fibrillation up to middle-age than those with corresponding normal birth outcomes," says principal investigator Krisztina Laszlo, associate professor at the Department of Global Public Health, Karolinska Institute, and senior lecturer at the Department of Public Health and Caring Sciences at Uppsala University.

"Individuals who were small for gestational age at birth had an increased risk of atrial fibrillation up to the age of 18, but not later in adulthood."

The risk increase was 30 per cent for individuals born preterm, 55 per cent for individuals who were large at birth and 71 per cent for individuals who were both preterm and large for gestational age at birth.

The results of the study are based on statistical analyses of over eight million births from Danish (1978-2016), Finnish (1987-2014) and Swedish (1973-2014) medical birth registries who were followed for incident atrial fibrillation in the national patient and cause of death registries up to 2021.

The results were compared with siblings in the same families. Since the study was observational, no causal relationships could be ascertained.

The researchers say that future studies may investigate the association between preterm birth, foetal growth, and the risk of atrial fibrillation up to old age.