Cardiometabolic and pulmonary health in adults born preterm with very low birth weight - A-two-country birth cohort study

This doctoral thesis found early signs of accelerated ageing of cardiovascular and pulmonary health in adults born very preterm with very low birth weight. Most individuals born preterm with very low birth weight (<1500 g) live healthy and functional lives.

However, long-term health trajectories up to mid-adulthood remain incompletely understood. The aim of this thesis was to examine body composition, lung function, and cardiac autonomic regulation in adults born preterm with very low birth weight who were approaching middle age, compared with term-born controls.

The study comprised three sub-studies using two birth cohorts: the Helsinki Study of Very Low Birth Weight Adults (“Pikku-k”, Finland) and the NTNU Low Birth Weight in a Lifetime Perspective Study (Norway). Using harmonised methods, 137 adults born preterm and 158 full-term controls were examined at a mean age of 36 years. Results from body composition assessments and lung function tests were also compared with data collected in young adulthood to assess longitudinal changes.

Adults born preterm had lower fat-free mass and were shorter than controls. Body mass index and body fat percentage did not differ between the groups. Fat mass increased from young adulthood to mid-adulthood in both groups, but fat-free mass remained lower in adults born preterm. Adults born preterm had poorer lung function at both assessment time points. A steeper decline in forced expiratory volume and vital capacity was observed in those who had been diagnosed with bronchopulmonary dysplasia in infancy.

In mid-adulthood, women born preterm showed signs of changes in cardiac autonomic regulation, including a higher resting heart rate and changes indicative of impaired parasympathetic nervous system regulation. Changes in heart rate variability partly explained the association between preterm birth and elevated blood pressure.

As the first generations of individuals who received neonatal intensive care are reaching middle age, this population provides a unique opportunity to study the long-term effects of early-life conditions on ageing. There are currently no official recommendations for the clinical follow-up of adults born very preterm. Nevertheless, preterm birth and other perinatal risk factors should be assessed as part of patients’ medical history in healthcare settings, in order to appropriately target potential further investigations.