title: Morning cortisol does not mediate the association of size at birth with blood pressure in children born from full-term pregnancies.
abstract: OBJECTIVE
  It had been suggested that programming of the hypothalamo-pituitary-adrenal axis may underlie the associations of reduced size at birth with raised blood pressure in later life. We investigated whether morning salivary cortisol mediates the inverse association of birthweight with systolic blood pressure in children.
  
  
  METHODS
  Subjects and measurements--a historical cohort study involving 1152 Swedish children aged 5-14 years, who took part in a family study comprised of mother, father, and two full-sibs delivered in 1987-1995 after 38-41 weeks gestation within 36 months of each other. Birthweight and gestational age were available from obstetric records. Blood pressure, weight, height and puberty stage were measured at a clinic. Cortisol was measured by radioimmunoassay in morning salivary samples taken at home, within 30 min of waking.
  
  
  RESULTS
  Morning cortisol showed a weak negative association with length of gestation in siblings, was not related to birthweight or to systolic or diastolic blood pressure. There was no change in the strength of the negative association between birthweight and systolic blood pressure on adjustment for cortisol (-1.4 mmHg/kg, 95% CI -2.7, -0.2; adjusted for age, sex, puberty stage, weight and height, and cortisol).
  
  
  CONCLUSIONS
  Morning cortisol was not associated with size at birth, and did not mediate the birthweight-blood pressure association in children born from full-term pregnancies. It is possible that basal cortisol levels are of more importance in explaining associations of size at birth with later blood pressure in older subjects, or in populations with more varied length of gestation. Alternatively, our results may be caused by misclassification of the hypothalamo-pituitary-adrenal activity.
authors.affiliation: Stockholm University/Karolinska Institute, Centre for Health Equity Studies, Stockholm, Sweden. ilona.koupil@chess.su.se
authors.forename: Ilona
authors.initials: I
authors.lastname: Koupil
authors.forename: Vera
authors.initials: V
authors.lastname: Mann
authors.forename: David A
authors.initials: DA
authors.lastname: Leon
authors.forename: Ulf
authors.initials: U
authors.lastname: Lundberg
authors.forename: Liisa
authors.initials: L
authors.lastname: Byberg
authors.forename: Denny
authors.initials: D
authors.lastname: Vågerö
mesh_terms: D000293:Adolescent; D001724:Birth Weight; D001794:Blood Pressure / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D002940:Circadian Rhythm; D005260:Female; D006306:Health Surveys; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D007231:Infant, Newborn; D016014:Linear Models; D008297:Male; D011247:Pregnancy; D013548:Sweden; D013599:Systole; D047929:Term Birth
chemical_list: D006854:Hydrocortisone