Risk of high blood pressure among young men increases with the degree of immaturity at birth

Background - Survivors of preterm birth constitute a new generation of young adults, but little is known about their long- term health. We investigated the association between gestational age ( GA) and risk of high blood pressure ( HBP) in young Swedish men and whether GA modified the risk of HBP; ie, whether HBP was related to being born small for gestational age ( SGA). Methods and Results - This population- based cohort study included 329 495 Swedish men born in 1973 to 1981 who were conscripted for military service in 1993 to 2001. Multivariate linear- and logistic- regression analyses were performed. Main outcome measures were systolic and diastolic BPs at conscription. Linear- regression analyses showed that systolic BP increased with decreasing GA ( regression coefficient - 0.31 mm Hg/ wk, P < 0.001). Systolic and diastolic BPs both increased with decreasing birth weight for GA, but the association with systolic BP was most evident ( regression coefficient - 0.67 mm Hg per SD score in birth weight for GA, P < 0.001). Compared with men born at term ( GA, 37 to 41 weeks), the adjusted odd ratios ( 95% confidence intervals [ CIs]) for high systolic BP ( >= 140 mm Hg) were as follows: moderately preterm ( 33 to 36 weeks), 1.25 ( 1.19 to 1.30); very preterm ( 29 to 32 weeks), 1.48 ( 1.30 to 1.68); and extremely preterm ( 24 to 28 weeks), 1.93 ( 1.34 to 2.76). Being SGA was associated only with an increased risk of high systolic BP among men born at 33 weeks or later. The risk estimates for high diastolic BP ( >= 90 mm Hg) increased with decreasing GA, but the risk reached significance only among men born moderately preterm. Conclusions - Preterm birth, a common pregnancy complication, is a risk factor for HBP in young men. The risk of high systolic BP associated with birth weight for GA is modified by GA, suggesting that perinatal contributions to BP elevation later in life may be induced by different biological pathways.