Adults born preterm have higher blood pressure (BP) than those born at
term. Most studies have focused on preterm birth, and few have assessed
BP variability, an independent risk factor of cardiovascular disease. We
studied the association of preterm birth with 24-hour ambulatory BP,
measured by an oscillometric device, in 42 young adults born early
preterm (<34 weeks), 72 born late preterm (34-36 weeks), and 103
controls (≥37 weeks). Sleep was confirmed with accelerometry in 72.4% of
subjects. The 24-hour systolic BP of adults born early preterm was 5.5
mm Hg higher (95% confidence interval, 1.9-9.3), awake systolic BP was
6.4 mm Hg higher (95% confidence interval, 2.8-10.1), and sleeping
systolic BP was 2.9 mm Hg higher (95% confidence interval 0.3-7.5) when
adjusted for age, sex, and use of accelerometry. The differences
remained similar when adjusted for height, body mass index, physical
activity, smoking, parental education, maternal body mass index, smoking
during pregnancy, and gestational diabetes mellitus and attenuated
slightly when adjusted for maternal hypertensive pregnancy disorders.
Adults born early preterm also had higher BP variability as indicated by
higher individual standard deviations of systolic BP and diastolic BP.
Although our results were consistent with a dose-response relationship
between shorter gestation and higher BP, the difference between the late
preterm and term groups was not statistically significant. Our results
suggest that the higher BP in adults born early preterm is present
during both waking and sleeping hours, may be more pronounced during
waking hours, and is accompanied by higher individual BP variability.