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 Background While the relation of salt intake with blood pressure (BP) is linear, it is U-shaped for mortality and cardiovascular disease (CVD). Purpose 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. Methods 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 birth weight, 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 birth weight 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 birth weight. Multivariable-adjusted hazard ratios were not significant for any endpoint in any of the BW, UVNA and UNAK strata. Adult body weight tracked with birth weight (P<0.0001). The partial r in the low birth weight group associating changes from baseline to follow-up in UVNA and systolic BP was 0.68 (P=0.023), but not significant in other birth weight groups. Conclusion This study did not substantiate its prior hypothesis, but showed tracking of adult with birth weight and suggest that low birth weight increases salt sensitivity.Figure 1Figure 2