The association between urine-estimated salt intake and hypertension: findings of a population-based study

Background: This cross-sectional study investigated the multi-stage and phenotype-specific association between urine-estimated salt intake and hypertension (HTN) in the Tehran Lipid and Glucose Study. Methods: Adult participants (n = 1,782, mean age of 43.0 +/- 13.7 years and 46.0% were men) were recruited (2015-2017) for 24-hour urine (24hU)-estimated salt intake and blood pressure (BP) measurements. Multivariable-adjusted multinomial logistic regression was used to estimate the association between 24hU-estimated salt intake (quintile categories and per each 1 g increment over recommended level) and HTN stages (Pre-HTN, stage 1 [S-1-HTN], and stage 2 [S-2-HTN]) and HTN phenotypes (isolated systolic HTN [ISH], isolated diastolic HTN [IDH], and systolic-diastolic HTN [SDH]). Results: The prevalence of Pre-HTN, S-1- and S-2-HTN was 5.7%, 29.3%, and 9.1%, respectively. The prevalence of ISH, IDH, and SDH was 2.5%, 27.9%, and 8.0%, respectively. 24hU-estimated salt intake > 10.9 vs. < 6.7 g/day was associated with an elevated probability of Pre-HTN and S-1-HTN, IDH, and SDH by 2.50, 1.65, 1.74, and 2.03-fold, respectively. Every 1 g-increment of salt intake over 5 g/day was associated with an increased chance of having Pre-HTN, S-1-HTN, and IDH by 15%, 8%, and 8%, respectively. Conclusions: The contribution of high salt intake to the development of HTN might be more pronounced during the initial stages of BP elevation, potentially impacting diastolic BP to a greater extent than systolic BP.