Birth weight influences blood pressure values and variability in children and adolescents

The objective of the present study was to assess the relationships between birth weight and the values and variability of ambulatory blood pressure. S ix hundred thirty healthy children (369 girls) age 4 to 18 years (mean, 9.9 years) born at term after a normotensive pregnancy were included. The subj ects were divided into 5 groups according to birth weight. For each subject , a 24-hour ambulatory blood pressure monitoring was performed according to the protocol designed. Average and variability (estimated as the standard deviation) of ambulatory blood pressure and heart rate were calculated sepa rately for 24-hour, daytime, and nighttime periods. When values were adjust ed for gender, current age, weight, and height, children with the lowest bi rth weights had the highest ambulatory blood pressure values and variabilit y, whereas no differences in heart rate were observed. Multiple regression analysis showed that although current weight was the strongest predictor fo r 24-hour systolic blood pressure (P<0.001), there was also an independent and significant inverse relationship for birth weight (P<0.002) after contr olling for gender, current age, and height. Likewise, birth weight was inde pendently and inversely correlated with 24-hour systolic blood pressure var iability (P<0.03). In conclusion, children who had lower birth weights tend ed to have not only the highest blood pressure values but also the highest blood pressure variability, independent of the increases in ambulatory bloo d pressure values. Knowing, that high blood pressure variability is at leas t partially independent of blood pressure values, the importance of this va riability on further blood pressure rises and/or on vascular damage later i n life needs to be assessed in future studies.