BLOOD PRESSURE AND CARDIOVASCULAR RISK IN RELATION TO BIRTH WEIGHT AND URINARY SODIUM: AN INDIVIDUAL-PARTICIPANT META-ANALYSIS OF EUROPEAN FAMILY-BASED POPULATION STUDIES

Abstract

Objective: While the relation of salt intake with blood pressure (BP) is linear, it is U shaped for mortality and cardiovascular disease (CVD). This individual-participant meta-analysis explored whether the relation of hypertension, death or CVD with 24 h urinary sodium excretion (UVNA) or sodium-to-potassium (UNAK) ratio was modified by birth weight (BW). Design and method: Families were randomly enrolled in the Flemish Study on Genes, Environment and Health Outcomes (1985-2004) and the European Project on Genes in Hypertension (1999-2001). Categories of BW, UVNA and UNAK (< = 2500, >2500-4000, >4000 g; <2.3, 2.3-4.6 and >4.6 g; and <1, 1-2, >2, respectively) were coded using deviation-from-mean coding and analyzed by Kaplan-Meier survival functions and linear and Cox regression. Results: The study population was subdivided into the Outcome (n = 1945), Hypertension (n = 1460) and BP cohorts (n = 1039) to analyze the incidence of mortality and cardiovascular endpoints, hypertension and BP changes as function of UVNA changes. The prevalence of low/medium/high BW in the Outcome Cohort was 5.8/84.5/9.7%. Over 16.7 years (median), rates were 4.9%, 8.0% and 27.1% for mortality, CVD and hypertension, respectively, but were not associated with BW. Multivariable-adjusted hazard ratios were not significant for any endpoint in any of the BW, UVNA and UNAK strata. Adult body weight tracked with BW (P<0.0001). The partial r in the low BW group associating changes from baseline to follow-up in UVNA and systolic BP was 0.68 (P = 0.023), but not significant in other BW groups. Conclusions: This study did not substantiate its prior hypothesis, but showed tracking of adult with birth weight and suggest that low BW increases salt sensitivity.