Antenatal Steroid Exposure, Aerobic Fitness, and Physical Activity in Adolescents Born Preterm with Very Low Birth Weight.

OBJECTIVE: To determine whether antenatal corticosteroid exposure is associated with aerobic fitness or physical activity participation in adolescents born preterm with very low birth weight (VLBW). STUDY DESIGN: Observational cohort study of 14-year-old adolescents (n = 173) born with VLBW between 1992 and 1996 at a regional perinatal center with 91 exposed to antenatal corticosteroids. Aerobic fitness was determined from peak oxygen uptake (V˙O2peak) obtained via maximal exercise testing on a cycle ergometer. Physical activity levels for the past year and past 2 months were estimated from a questionnaire. Between-group comparisons for continuous variables were evaluated using independent t tests or Mann-Whitney U tests. Generalized linear models were used to compare differences in fitness and physical activity between those exposed to antenatal corticosteroids and not exposed to antenatal corticosteroids, with race and sex in models. RESULTS: Regression analysis revealed an antenatal corticosteroids × sex × race interaction for V˙O2peak (P ≤ .001). Nonblack male adolescents exposed to antenatal corticosteroids had significantly greater V˙O2peak than nonblack male adolescents not exposed to antenatal corticosteroids expressed relative to body mass (mean difference [95% CI]; 8.5 [2.1-15.0] mL·kg-1·min-1) and lean body mass (9.0 [1.1-16.9] mL·kglean body mass-1·min-1). No antenatal corticosteroid group differences in V˙O2peak were evident in black male adolescents, or black and nonblack female adolescents. Male adolescents exposed to antenatal corticosteroids reported participating in significantly more total physical activity (medians: 14.6 vs 8.5) and vigorous physical activity (3.0 vs 0.95) per week for the past 2 months than male adolescents not exposed to antenatal corticosteroids. CONCLUSIONS: Exposure to antenatal corticosteroids was associated with greater physical activity participation and aerobic fitness in adolescents with VLBW, particularly in nonblack male adolescents, which may confer health benefits in this at-risk population.

Obesity is Associated with Higher Blood Pressure and Higher Levels of Angiotensin II but Lower Angiotensin-(1-7) in Adolescents Born Preterm.

OBJECTIVES: To evaluate if obesity is associated with increased angiotensin II (Ang II) and decreased angiotensin-(1-7) or Ang-(1-7) in the circulation and urine among adolescents born prematurely. STUDY DESIGN: In a cross-sectional analysis of 175 14-year-olds born preterm with very low birth weight, we quantified plasma and urinary Ang II and Ang-(1-7) and compared their levels between subjects with overweight/obesity (body mass index ≥85th percentile, n = 61) and those with body mass index <85th percentile (n = 114) using generalized linear models, adjusted for race and antenatal corticosteroid exposure. RESULTS: Overweight/obesity was associated with higher systolic blood pressure and a greater proportion with high blood pressure. After adjustment for confounders, overweight/obesity was associated with an elevated ratio of plasma Ang II to Ang-(1-7) (ß: 0.57, 95% CI 0.23-0.91) and higher Ang II (ß: 0.21 pmol/L, 95% CI 0.03-0.39) but lower Ang-(1-7) (ß: -0.37 pmol/L, 95% CI -0.7 to -0.04). Overweight/obesity was associated with a higher ratio of urinary Ang II to Ang-(1-7) (ß: 0.21, 95% CI -0.02 to 0.44), an effect that approached statistical significance. CONCLUSIONS: Among preterm-born adolescents, overweight/obesity was associated with increased Ang II but reduced Ang-(1-7) in the circulation and the kidney as well as higher blood pressure. Obesity may compound the increased risk of hypertension and cardiovascular disease in individuals born prematurely by further augmenting the prematurity-associated imbalance in the renin-angiotensin system.

Preterm Birth Is Associated with Higher Uric Acid Levels in Adolescents.

OBJECTIVE: To compare serum uric acid levels in adolescents born prematurely and adolescents born at term and to assess the correlation between serum uric acid and blood pressure (BP) in those born prematurely. STUDY DESIGN: In this observational cohort study, 124 adolescents born prematurely and 44 adolescents born at term were studied at 14 years of age. Multivariate analyses were used to describe the relationship of premature birth to serum uric acid while adjusting for confounding variables. Pearson correlation was used to describe the relationship between uric acid and systolic BP among those born prematurely. RESULTS: Adjusting for race, sex, maternal hypertension, and fetal growth, we found that preterm adolescents had greater serum uric acid levels than adolescents born at term (adjusted mean difference 0.46, 95% CI 0.10-0.81 mg/dL; 27.4, 6-48.2 µmol/L; P = .012). Among those born prematurely, uric acid was positively correlated with systolic BP (Pearson correlation coefficient: 0.29, 0.12-0.44; P = .0013). CONCLUSIONS: Serum uric acid levels are greater in adolescents born prematurely than in those born at term, and this difference could contribute to greater BP among individuals born prematurely.

Adiposity in adolescent offspring born prematurely to mothers with preeclampsia.

OBJECTIVE: To evaluate the relationship between maternal preeclampsia resulting in premature delivery and adiposity in the offspring during adolescence. STUDY DESIGN: The 172 study participants were 14 years old and had very low birth weight. We compared height, weight, body mass index (BMI), percent fat, waist circumference, and triceps and subscapular skin fold thicknesses between those born prematurely secondary to preeclampsia (n = 51; 22 male) and those born prematurely after normotensive pregnancies (n = 121; 55 male). Multiple linear regression analysis was used to adjust for potential confounders (maternal BMI, antenatal steroid exposure, and race) and to evaluate potential explanatory variables (fetal, infancy, and childhood weight gain, and caloric intake, level of fitness, and physical activity at 14 years). RESULTS: When adjusted for potential prenatal confounders (antenatal steroid exposure and race), adolescent male offspring of preeclamptic pregnancies had higher BMI (4.0 kg/m(2) [1.5, 6.6]) (mean difference [95% CI]), waist circumference (11.8 cm [3.8, 19.7]), triceps (4.6 mm [0.6, 8.6]) and subscapular skinfold thicknesses (6.2 mm [1.5, 10.9]), and percent body fat (4.1% [-0.1, 8.3]). Adjusting for infancy and childhood weight gain attenuated these group differences. There were no group differences among females. CONCLUSION: Male adolescent offspring born prematurely of women with preeclampsia have higher measures of adiposity than those born prematurely of normotensive pregnancies.

Aerobic fitness and physical activity levels of children born prematurely following randomization to postnatal dexamethasone.

OBJECTIVE: To investigate the effects of postnatal dexamethasone treatment on aerobic fitness and physical activity levels in school-aged children born with very low birth weight (VLBW). STUDY DESIGN: This was a follow-up study of 65 VLBW infants who participated in a randomized controlled trial of dexamethasone (DEX) to reduce ventilator dependency. Aerobic fitness was determined from peak oxygen uptake (VO(2peak)) with a cycle ergometer. Habitual physical activity was assessed by questionnaire. RESULTS: A trend for a treatment with an interaction between treatment and of diagnosis of chronic lung disease (CLD) was found, with the children in the placebo group with CLD having the lowest VO(2peak) (P = .09). Reduced fitness was seen in 53% of the group treated with DEX and 48% of the group given placebo. No between-group differences in physical activity were seen. Parental reports suggested that nearly two-thirds of the children participated in < 1 hour per week of vigorous physical activity, which was explained in part by decreased large airway function (r = 0.30; P = .03). CONCLUSIONS: We found no adverse effect of postnatal DEX on aerobic fitness or habitual physical activity at school age. However, the reduced fitness and physical activity levels emphasize the need for closer follow-up and early interventions promoting physical activity to reduce the risk of chronic disease in this at-risk population.

Follow-up study of a randomized controlled trial of postnatal dexamethasone therapy in very low birth weight infants: effects on pulmonary outcomes at age 8 to 11 years.

OBJECTIVE: To determine whether postnatal dexamethasone (DEX) exposure affects pulmonary outcomes at school age in children born with very low birth weight (VLBW). STUDY DESIGN: Follow-up study of 68 VLBW children who participated in a randomized controlled trial of postnatal DEX. Pulmonary function was assessed by spirometry. Current asthma status was obtained from a parent. RESULTS: Sixty-eight percent of the placebo group had below-normal forced expiratory volume in 1 second (FEV1), compared with 40% of the DEX group (chi2 = 4.84; P = .03), with trends for lower forced vital capacity (FVC) and FEV1 values in the placebo group. Fifty percent of the placebo group and 34% of DEX group had below normal FEV1/FVC (chi2 =1.59; P =.21). Parent-reported prevalence of asthma did not differ between groups. Logistic regression analysis suggested that the positive effects of DEX on pulmonary function at follow-up were mediated in part by shortened exposure to mechanical ventilation. CONCLUSIONS: Postnatal DEX exposure was associated with higher expiratory flow with no adverse effects on pulmonary outcomes at school age. The prevalences of asthma and impaired pulmonary function underscore the influence of neonatal illness on health at school age, and stress the importance of repeated follow-up examinations of these children.

Evidence based physical activity for school-age youth.

OBJECTIVES: To review the effects of physical activity on health and behavior outcomes and develop evidence-based recommendations for physical activity in youth. STUDY DESIGN: A systematic literature review identified 850 articles; additional papers were identified by the expert panelists. Articles in the identified outcome areas were reviewed, evaluated and summarized by an expert panelist. The strength of the evidence, conclusions, key issues, and gaps in the evidence were abstracted in a standardized format and presented and discussed by panelists and organizational representatives. RESULTS: Most intervention studies used supervised programs of moderate to vigorous physical activity of 30 to 45 minutes duration 3 to 5 days per week. The panel believed that a greater amount of physical activity would be necessary to achieve similar beneficial effects on health and behavioral outcomes in ordinary daily circumstances (typically intermittent and unsupervised activity). CONCLUSION: School-age youth should participate daily in 60 minutes or more of moderate to vigorous physical activity that is developmentally appropriate, enjoyable, and involves a variety of activities.