This study investigates the influence of age and gender on the relationship between birth weight and blood pressure in childhood, using casual and 24-h blood pressure measurements. Casual and 24-h blood pressure were measured on 976 normal schoolchildren (550 girls) aged 6 to 16 years. There was no significant association between birth weight and casual systolic blood pressure (regression coefficient (ss)=-0.30; 95% CI -1.79, 1.19). There was a significant negative correlation between birth weight and mean 24-h systolic blood pressure (ss=-2.13; 95% CI -3.35, -0.90). Subgroup analysis by gender revealed a significant relation for girls (ss=-2.88; 95% CI -4.44, -1.32) but not boys (ss= -1.02; 95% CI -2.99, 0.95). ). Subgroup analysis by age group revealed a significant relation for > or =11 years old (ss= -3.17, 95% CI -4.86, -1.48) but not children <11 years old (ss= -0.88; 95% CI -2.63, 0.88). Interaction tests demonstrated a statistically significant different relationship between birth weight and blood pressure for boys and girls ( P=0.021) and for children <11 and > or = 11 years of age ( P=0.036).
Conclusion: this study demonstrates that gender and age have an important influence on the relationship between birth weight and blood pressure in childhood. The observed differences between boys and girls and the different age groups remain unexplained.