Sodium intake in infancy and blood pressure at 7 years: findings from the Avon Longitudinal Study of Parents and Children

Background: Infancy may be a sensitive period regarding effects of sodium intake on future blood pressure (BP). This has only been demonstrated in one randomized trial of low sodium formulae with follow-up in adolescence in one-third of participants. Objective: To prospectively assess associations between sodium intake in infancy and BP at 7 years in the Avon Longitudinal Study of Parents and Children (ALSPAC). Subjects: A total of 533 children with sodium data at 4 months and 710 children with sodium at 8 months. Results: 0.4% of participants at 4 months and 73.0% at 8 months exceeded recommended levels for infant sodium intake. After minimal adjustment (child age, sex, energy), sodium intake at 4 months was positively associated with systolic blood pressure (SBP) at 7 years (beta = 0.54mm Hg/mmol; 95% CI: 0.09, 0.98mm Hg; P = 0.02). This changed little following adjustment for confounders but attenuated after adjusting for breastfeeding. This association was not mediated by sodium intake at 7 years. Due to high sodium-potassium correlations, effects of sodium independent of potassium could not be estimated with reasonable precision. Sodium intake neither at 8 months nor at 7 years was associated with SBP at 7 years. Conclusion: The association between sodium intake at 4 months and future SBP requires replication in studies that can control for effects of potassium before we can conclude that early infancy is a sensitive period with respect to effects of sodium on future BP. The majority of infants exceeded recommended levels of sodium intake at 8 months, and interventions to reduce sodium in infants' diets should be considered.