Study links low birthweight to increased stroke risk in young adults, independent of BMI and gestational age

In new research to be presented at this year’s European Congress on Obesity (ECO2026) in Istanbul, Turkey (12–15 May), researchers show an increased risk of stroke in young adulthood for children of low birthweight, independent of their body mass index (BMI) as young adults or gestational age at birth. The study of almost 800,000 people in Sweden suggests that low birthweight could be included in stroke risk assessment for adults, say the authors, who include Dr. Lina Lilja and Dr. Maria Bygdell of the University of Gothenburg, Gothenburg, Sweden, and colleagues.

While the incidence of stroke overall has declined in high income countries over the past decades, this decline has been less pronounced among young and middle-aged adults compared to older adults. In some regions and in these younger age groups, stroke incidence is even rising—including lower-income countries of southeast Asia and Oceania, and high-income countries including Sweden, the US, and the UK.

Thus, the authors decided to investigate whether factors such as birthweight, gestational age at birth, and BMI as a young adult could be risk factors for stroke in younger adults. While for young adults these life events have already passed, for children not yet conceived, these are factors that could be targeted with interventions.

Stroke types and study design

The authors investigated both common forms of stroke—ischemic, caused by a blockage of blood vessels in the brain (representing more than three-quarters of strokes, depending on location); and intercerebral hemorrhage (ICH/”brain bleed”) strokes, representing up to a quarter of all strokes.

This population-based study included 420,173 men and 348,758 women born between 1973 and 1982 in Sweden (and thus aged 43 to 53 years if still alive today and representing all recorded live births from those years) with data on birth weight, gestational age, and BMI in young adulthood from the Medical Birth Register and the National Conscription register, respectively. Study participants were followed until December 31, 2022.

Information on early adult stroke events was retrieved from the National Patient Register and the Cause of Death Register in Sweden—2,252 first stroke events, mean age 36 years; 1,624 ischemic stroke [IS] events, mean age 37 years; and 588 intracerebral hemorrhage stroke [ICH] events, mean age 33 years (with 40 of these first stroke events uncategorized).

Findings on birthweight and risk

Since registration of diagnoses in these registers is mandatory, they provide comprehensive national data on individuals who have been hospitalized or died from stroke. The relatively low numbers of events reflect that these are younger adults, in whom absolute stroke risk is lower. All analyses were adjusted for gender, birth year, gestational age, parents’ country of birth, and age at adult BMI.

The authors found that there was a 21% increased risk for all stroke events combined, as well as for ischemic stroke alone, and a 27% increased risk of intracerebral hemorrhage stroke alone, for individuals (men and women combined) having a birth weight below median (3.5 kg) compared to individuals having a birth weight above the median. Women with a birth weight below median (3.5 kg) had an 18% increased risk for all strokes combined, and men a 23% increased risk compared to individuals with a birth weight above median.

The results were independent of gestational age (how long the child had been in the womb before birth) and their BMI as a young adult. Gestational age was not itself associated with stroke risk. The overall results in each case were similar for women and men.

The authors conclude, “We demonstrate that lower birthweight is associated with an increased risk of early adult stroke. There is similar increased risk for both men and women and for both the major types of stroke, ischemic and hemorrhagic, and the results were independent of gestational age at birth, and BMI as young adults. These findings suggest that low birth weight may be included in assessments of stroke risk in adults.”

Provided by
European Association for the Study of Obesity