BackgroundIncreasing numbers of survivors of preterm birth are growing into adulthood today. Long-term health-effects of prematurity are still poorly understood, but include increased risk for diabetes, obesity and cardiovascular diseases in adult life. To test if reduced physical fitness may be a link in the causal chain of preterm birth and diseases in later life, the association of preterm birth and adult exercise capacity was investigated. The hypothesis was that preterm birth contributes independently of other risk factors to lower physical fitness in adulthood.Methods and FindingsPopulation-based national cohort study of all males conscripting for military service in 1993–2001 and born in Sweden 1973–1983, n = 218,820. Data were retrieved from the Swedish Conscript Register, the Medical Birth Register and the Population and Housing Census 1990. Primary outcome was the results from maximal exercise test (Wmax in Watt) performed at conscription. Association to perinatal and socioeconomic risk factors, other co-variates and confounders were analysed. General linear modelling showed that preterm birth predicted low Wmax in a dose-response related pattern, with 25 Watt reduction in Wmax for the lowest gestational ages, those born ≤27 weeks. Low birth weight for gestational age also independently predicted low Wmax compared to normal and high birth weight (32 Watt reduction for those with a birth weight Standard Deviation Score <2). Low parental education was significantly associated with reduced Wmax (range 17 Watt), as well as both low and high current BMI, with severe obesity resulting in a 16 Watt deficit compared to Wmax top performance.ConclusionBeing born preterm as well as being born small for gestational age predicts low exercise capacity in otherwise healthy young men. The effect size of being born preterm equal or exceed that of other known risk factors for unfitness in adults, such as low parental education and overweight.

Short running head: Physiology of impaired gas exchange in BPD Descriptor: 14.3 Manuscript Body Word Count: 3639 At a Glance Commentary: Scientific Knowledge on the Subject: Assessment of impaired gas exchange may provide a continuous outcome measure for sensitive and equitable determination of severity of bronchopulmonary dysplasia (BPD). Previous gas exchange studies in BPD infants used small cohorts and targeted moderate-severe BPD. These studies show right shift of the peripheral oxyhemoglobin saturation (SpO2) versus inspired oxygen partial pressure (PIO2) curve and reduced ventilation-perfusion ratio reliably predict hypoxaemia in preterm infants breathing air, and further, that many infants also have a right-left shunt. What This Study Adds to the Field: We provide measures of right shift, ventilation/perfusion and shunt, across the full spectrum of lung disease in a large (n=219) group of preterm infants. Shift increases and ventilation/perfusion decreases with increased severity of BPD as defined by the NIH classification of BPD. Shunt is primarily a feature of infants with moderate-severe BPD who require supplemental oxygen. Non-invasive bedside assessment of shift, ventilation/perfusion and shunt provide physiological continuous outcome measures of severity of respiratory disease in very preterm infants with/without BPD independent of altitude and unit practices. Routine analysis of the SpO2/PIO2 curve may improve accuracy of BPD severity classification and provide a sensitive continuous outcome measure for clinical trials evaluating pulmonary outcomes.

BackgroundPreterm birth is a risk factor for decreased exercise capacity and impaired cognitive functions in later life. The objective of this study was to disentangle the associations between preterm birth, physical fitness and cognitive performance in young adulthood.MethodsThis population-based cohort study included 218,802 young men born in Sweden 1973–1983. Data on birth characteristics was obtained from the Medical Birth Register and linked to exercise capacity assessed by ergometer cycling and cognitive tests performed at conscription for military service in 1993–2001. Cognitive performance was assessed using stanine (STAndard NINE) scores. The results were adjusted for socioeconomic factors.ResultsExercise capacity was positively associated with cognitive performance across all gestational ages. The sub-group of men who were born extremely preterm (gestational age <28 weeks) and had low exercise capacity exhibited the lowest odds ratio (OR = 0.26, 95%CI:0.09–0.82) of having a cognitive function above the mean stanine score (2.9) for men born at term with normal birth weight. Men born extremely preterm with a high exercise capacity had similar or even higher ORs for cognitive function (OR = 0.59; 95% CI:0.35–0.99) than men born at term with low Wmax (OR = 0.57; 95% CI:0.55–0.59).ConclusionsPhysical fitness is associated with higher cognitive function at all gestational ages, also in young men born extremely preterm. Targeting early physical exercise may be a possible intervention to enhance cognitive performance and educational achievements in populations at risk, such as childhood and adult survivors of preterm birth.