Long-Term Impact of Preterm Birth on Exercise Capacity in Healthy Young Men: A National Population-Based Cohort Study

Abstract

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.

Physical Fitness in Young Adults Born Preterm

“…Several, although not all, 40 studies have shown lower cardiorespiratory fitness among children and young people born extremely (<28 weeks) or very (<32 weeks) preterm or at extremely or very low birth weight with the use of a maximal exercise test 10,11,[40][41][42][43] or a submaximal test 8,41 as in our study. A study in 218 820 Swedish male conscripts showed that among those born at 32 to 36 weeks, maximal exercise capacity was 0.10 SD lower than among those born at term 12 ; such a small difference would not have been detected in the current study. Together with these studies, our study suggests that lower levels of cardiorespiratory fitness are not present across the whole range of preterm births, at least at any meaningful level.…”

“…8,11 Few studies have assessed this in adolescents or adults born closer to term; a study in Swedish male conscripts was consistent with a graded relationship between lower length of gestation and lower maximal exercise capacity. 12 This question is important because both cardiorespiratory and muscular fitness are independent predictors of cardiometabolic and musculoskeletal health [13][14][15] and lower late-life mortality. 16,17 We studied the association of early (<34 weeks) and late (34-36 weeks) preterm birth with muscular, cardiorespiratory, and self-rated physical fitness among young adults.…”

Lung consequences in adults born prematurely

“…To date, studies undertaken to characterise exercise capacity in adults born preterm have been relatively small with conflicting findings 47 55 67. A large population-based national cohort study of male army conscripts reported preterm birth as an independent predictor of reduced exercise capacity 67.…”

“…A large population-based national cohort study of male army conscripts reported preterm birth as an independent predictor of reduced exercise capacity 67. Narang and colleagues reported no significant difference in exercise capacity between those born preterm and term controls 55…”

Low Exercise Capacity Increases the Risk of Low Cognitive Function in Healthy Young Men Born Preterm: A Population-Based Cohort Study

“…Furthermore, their ability to or interest in physical activity may be affected, which may lead to a lower exercise capacity. This is further discussed in our previous study [13]. Even if exercise capacity is lower, Clemm and colleagues have shown that individuals born preterm do have the possibility to increase their exercise capacity with increased physical activity [14].…”