Size at birth and blood pressure in young adults: findings from a Brazilian birth cohort study

OBJECTIVE: To describe the prevalence of borderline blood pressure (BBP) and hypertension (HT) among young adults and to assess the association between size at birth and BBP/HT. METHODS: Data were collected from the first Ribeirao Preto Birth Cohort Study conducted in the city of Ribeirao Preto, southeastern Brazil, that started in 1978-1979. Of the 6,827 singletons born in hospitals, 2,060 were assessed at 23-25 years of age. Blood samples were collected, an anthropometric assessment was performed, and information was obtained regarding occupation, schooling, life habits and chronic diseases. Blood pressure (BP) was classified as: 1) BBP: systolic BP (SBP) >= 130 mm Hg and < 140 mm Hg and/or diastolic BP (DBP) >= 85 mm Hg and < 90 mm Hg; and 2) HT: SBP >= 140 mm Hg and/or DBP >= 90 mm Hg. A polytomic logistic regression model was used. RESULTS: BBP prevalence was 13.5% (males: 23.2%) and HT prevalence 9.5% (males: 17.7%). BBP was independently associated with male gender (relative risk [RR] 8.84; 95% CI 6.09; 12.82); birth length >= 50 cm (RR 1.97; 1.04;3.73); body mass index (BMI) >= 30 kg/m(2) (RR 3.23; 2.02; 5.15); and high waist circumference (RR 1.61; 1.13;2.29), while HT was associated with male gender (RR 15.18; 8.92;25.81); BMI >= 30 kg/m(2) (RR 3.68; 2.23; 6.06); high waist circumference (RR 2.68; 1.77;4.05); and elevated blood glucose (RR 2.55; 1.27; 5.10), but not with birth length. CONCLUSIONS: The prevalence of BBP and HT among young adults of this cohort was higher in males than females. Greater birth length was associated with BBP, but not with HT, whereas birth weight was not associated with either BBP or HT. Adult risk factors explained most of the increase in the levels of BBP and HT.