Drinking Water Salinity: Mineral Intake and Cardiovascular Health Open Access
Titu, Abu Mohd Naser (Spring 2018)
Abstract
Abstract
Drinking Water Salinity: Mineral Intake and Cardiovascular Health
Many coastal communities drink saline groundwater, which is a source of high sodium and other minerals. Groundwater salinity will increase in many coastal areas in future due to increased groundwater extraction and global climate change. Managed aquifer recharge (MAR), an intervention to lower drinking water salinity by infiltrating rainwater and pond water in order to dilute brackish aquifers, is a candidate solution for lowering drinking water salinity. The objective of this dissertation was to evaluate the health effects of access to MAR water on communities’ blood pressure, and to evaluate the association between drinking water salinity and blood pressure in southwest coastal Bangladesh using a stepped-wedge cluster randomized trial. This dissertation also assessed the association between drinking water chemical concentrations and blood pressure by analyzing the nationally representative surveys of Bangladesh.
The stepped-wedge trial enrolled 1,191 participants in 16 communities and conducted 5 visits between December 2016 and April 2017. Following baseline, 4 communities were randomly assigned to receive MAR water access in successive visits. We measured households’ drinking water electrical conductivity and participant’s blood pressure, weight and 24-hour urinary total protein, sodium, potassium, calcium, and magnesium. We used multilevel regression models to estimate effects of MAR water access and drinking water salinity on participants’ blood pressure. We analyzed blood pressure data of ≥35 year adults from the 2011 Bangladesh Demographic and Health Survey, and groundwater chemical concentrations data from the British Geological Survey (BGS) and the Department of Public Health Engineering (DPHE) survey 1998-1999 using survey estimation regression models to determine the association between drinking water chemical concentration and blood pressure.
Participants from communities randomized to have access to MAR water had 1.89 [95% Confidence Interval (CI): 0.51, 3.27; p=0.007] mmHg higher mean systolic blood pressure, and 1.39 [95% CI: 0.23, 2.55; p=0.018] mmHg higher mean diastolic blood pressure than communities with no access to MAR. Participants drinking moderately saline water [electrical conductivity: 2-10 μS/cm] had 1.60 [95% CI: 0.15, 3.04] mmHg lower mean systolic blood pressure and 1.21 [95% CI: 0.43, 1.99] mmHg lower mean diastolic blood pressure compared to fresh water drinkers [electrical conductivity <0.7 μS/cm]. Participants consuming moderately saline water had 17.57 [95% CI: 12.40, 22.74] mmol/day higher mean daily sodium, 0.32 [95% CI: -1.65, 2.28] mmol/day higher mean daily potassium, 1.23 [95% CI: 1.09, 1.39] times higher median daily calcium, and 1.28 [95% CI: 1.10, 1.48] times higher median daily magnesium in 24-hour urine compared to fresh water drinkers. Survey data analyses suggest the geometric mean ratio of systolic blood pressure for 10 mg/L increase in groundwater magnesium concentration was 0.992 (95% CI: 0.986, 0.999) after controlling for all chemicals and confounders but other chemicals were not associated with blood pressure.
Our findings show no evidence that MAR systems reduced blood pressure. We identified drinking water salinity and magnesium concentration in drinking water have an inverse association with blood pressure. Saline water is a source of cardio-protective minerals such as calcium and magnesium that may have blood pressure lowering effect. Salinity lowering interventions need to critically assess the contribution of drinking water to the daily intake of these minerals. Without remineralization of calcium and magnesium, lowering drinking water salinity may put people at risk for cardiovascular disease.
Table of Contents
Table of contents:
Chapter 1. Introduction.......... 11
Dissertation Aims.......... 14
Chapter 2. Stepped-wedge cluster-randomized controlled trial to assess the cardiovascular health effects of a managed aquifer recharge initiative to reduce drinking water salinity in southwest coastal Bangladesh: study design and rationale 15
Abstract.......... 16
Strengths and limitation of the study.......... 16
Introduction.......... 18
Objectives.......... 20
Methods.......... 21
Discussion.......... 28
Chapter 3. Cardiovascular and renal health effects of managed aquifer recharge to lower drinking water salinity in southwest coastal Bangladesh: a stepped-wedged cluster-randomized trial 36
Abstract.......... 38
Panel: Research into context.......... 39
Introduction.......... 41
Methods........... 42
Results............ 46
Discussion.......... 48
Chapter 4. Dose-response association of drinking water salinity with blood pressure and urinary protein excretion in southwest coastal Bangladesh 66
Abstract.......... 67
Introduction.......... 68
Methods.......... 70
Results.......... 74
Discussion.......... 76
Chapter 5: Groundwater chemistry and systolic blood pressure: a cross-sectional study in Bangladesh.......... 85
Abstract........... 86
Conclusions: Groundwater magnesium was negatively associated with SBP. Further research on drinking-water magnesium and blood pressure is warranted. 86
Introduction.......... 87
Methods........... 89
Results.......... 93
Discussion........... 95
Chapter 6. Summary, Reflections and Future Research.......... 107
Summary of findings........... 107
Reflections on study limitations and potential for improvements........... 108
Drinking water mineral concentrations.......... 108
Mineral intake through food........... 109
Follow-up of the cohort in wet season........... 109
Recommendation for future research ..........109
Selected planned future analyses during post-doctoral fellowship........... 110
References.......... 112
Appendix 1: Salt water intrusion into coastal aquifers due to marine reason across the world. Map downloaded from IGRAC (https://www.un-igrac.org/global-groundwater-information-system-ggis).......... 121
Appendix 2: Use of manage aquifer recharge (MAR) across the globe for different purposes. Map downloaded from IGRAC (https://www.un-igrac.org/global-groundwater-information-system-ggis.......... 122
Appendix 3: A pilot non-randomized longitudinal study of managed aquifer recharge initiative in southwest coastal Bangladesh: rationale, objectives and study design........... 123
Appendix 4: First do no harm: the need to explore potential adverse health implications of drinking rain water........... 126
Appendix 5: IRB approvals for conducting the stepped-wedge trial and DHS data analysis............ 130
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