Drinking Water Salinity, Urinary Macro-Mineral Excretions, and Blood Pressure in the Southwest Coastal Population of Bangladesh

Background-Sodium (Na+) in saline water may increase blood pressure (BP), but potassium (K+), calcium (Ca2+) and magnesium (Mg2+) may lower BP. We assessed the association between drinking water salinity and population BP. Methods and Results-We pooled 6487 BP measurements from 2 cohorts in coastal Bangladesh. We used multilevel linear models to estimate BP differences across water salinity categories: fresh water (electrical conductivity, <0.7 mS/cm), mild salinity (electrical conductivity >= 0.7 and <2 mS/cm), and moderate salinity (electrical conductivity >= 2 and <10 mS /cm). We assessed whether salinity categories were associated with hypertension using multilevel multinomial logistic models. Models included participant-, household-, and community-level random intercepts. Models were adjusted for age, sex, body mass index (BMI), physical activity, smoking, household wealth, alcohol consumption, sleep hours, religion, and salt consumption. We evaluated the 24-hour urinary minerals across salinity categories, and the associations between urinary minerals and BP using multilevel linear models. Compared with fresh water drinkers, mild-salinity water drinkers had lower mean systolic BP (-1.55 [95% CI: -3.22-0.12] mm Hg) and lower mean diastolic BP (-1.26 [95% CI: -2.21--0.32] mm Hg) adjusted models. The adjusted odds ratio among mild-salinity water drinkers for stage 1 hypertension was 0.60 (95% CI: 0.43-0.84) and for stage 2 hypertension was 0.56 (95% CI: 0.46-0.89). Mild-salinity water drinkers had high urinary Ca2+, and Mg2+, and both urinary Ca2+ and Mg2+ were associated with lower BP. Conclusions-Drinking mild-salinity water was associated with lower BP, which can be explained by higher intake of Ca2+ and Mg2+ through saline water.