Blood Pressure in Young Adults Born at Very Low Birth Weight: Adults Born Preterm International Collaboration

Adults born very preterm (VP; <32 weeks of gestation) or at very low birth weight (VLBW; <1500 g) have higher blood pressure than their peers born at term. A recent meta-analysis showed that VLBW or VP adults have on average 3.3 mm Hg higher systolic pressure than controls. Another meta-analysis, including studies in adults born at any degree of prematurity, concluded that the mean difference between adults born preterm and controls was 4.2 mm Hg for systolic and 2.6 mm Hg for diastolic blood pressure. These differences were more pronounced among women (systolic/diastolic 4.9/2.9 mm Hg) but clearly present among men as well (2.0/1.3 mm Hg). These differences are considerable given that, at the population level, a 2 mm Hg reduction in diastolic pressure is estimated to result in a 7% to 14% reduction in mortality from ischemic heart disease and 9% to 19% from stroke with greatest reductions in the youngest age groups. Although these meta-analyses have been important in confirming the association between very preterm birth and adult blood pressure, they have, apart from sex, not been able to assess any other risk factors or protective factors for high blood pressure among adults born very preterm. This would be a crucial step in identifying underlying mechanisms, which then could serve as targets for prevention. The higher blood pressure among adults born VLBW/VP could arise from dissimilar conditions that lead to preterm birth or Abstract—Adults born preterm at very low birth weight (VLBW; <1500 g) have higher blood pressure than those born at term. It is not known whether all VLBW adults are at risk or whether higher blood pressure could be attributed to some of the specific conditions underlying or accompanying preterm birth. To identify possible risk or protective factors, we combined individual-level data from 9 cohorts that measured blood pressure in young adults born at VLBW or with a more stringent birth weight criterion. In the absence of major heterogeneity, we performed linear regression analysis in our pooled sample of 1571 adults born at VLBW and 777 controls. Adults born at VLBW had 3.4 mm Hg (95% confidence interval, 2.2–4.6) higher systolic and 2.1 mm Hg (95% confidence interval, 1.3–3.0) higher diastolic pressure, with adjustment for age, sex, and cohort. The difference in systolic pressure was present in men (1.8 mm Hg; 95% confidence interval, 0.1–3.5) but was stronger in women (4.7 mm Hg; 95% confidence interval, 3.2–6.3). Among the VLBW group, blood pressure was unrelated to gestational age, maternal smoking, multiple pregnancy, retinopathy of prematurity, or bronchopulmonary dysplasia. Blood pressure was higher than that of controls among VLBW adults unexposed to maternal preeclampsia. Among those exposed, it was even higher, especially if born appropriate for gestational age. In conclusion, although female sex and maternal preeclampsia are additional risk factors, the risk of higher blood pressure is not limited to any etiologic subgroup of VLBW adults, arguing for vigilance in early detection of high blood pressure in all these individuals. (Hypertension. 2016;68:880-887. DOI: 10.1161/ HYPERTENSIONAHA.116.08167.) • Online Data Supplement