Cardiac autonomic function in adults born preterm with very low birth weight in mid‐adulthood—A two‐country birth cohort study

Cardiac autonomic functioning is altered in children and young adults born preterm with very low birth weight (VLBW; <1500 g). Whether these alterations persist into mid-adulthood remains unknown. We studied heart rate variability (HRV) in two birth cohorts, HeSVA (Finland) and NTNU LBW Life (Norway), with harmonized methods. HRV was assessed in 107 adults born preterm with VLBW and 142 controls born term with normal birth weight at a mean age of 36 (SD 3.3) years. We hypothesized that adults born preterm with VLBW have lower parasympathetic activity and higher blood pressure (BP), partly mediated by lower parasympathetic activity. Participants born preterm with VLBW had higher heart rate and BP than controls. In sex-stratified analyses, mean differences in high-frequency (HF) power were -43.3% (95% CI -63.9%, -11.3%) in women and -36.9% (-65.0%, 15.0%) in men. For root mean square of successive differences, differences were -18.2% (-35.6%, 4.1%) in women and 18.5% (-10.4%, 58.4%) in men. Low-frequency (LF) power differed by -23.7% (-46.2%, 10.5%) in women and 35.0% (-16.5%, 120.3%) in men. LF/HF ratio was 36.3% (4.1%, 76.8%) higher in women and -13.9% (-34.3%, 12.7%) in men. Among women, elevated BP was partly mediated by HRV. Findings suggest altered autonomic regulation in adults born preterm with VLBW, especially women, potentially contributing to higher BP.