Drinking water salinity and blood pressure in coastal Bangladesh: follow-up of a population-based cohort in a climate-vulnerable region
Aneire E Khan, Eurydice Costopoulos, Sontosh Kumar Mojumder, Asma Begum Shilpi, Mohammad A Hoque, Adrian Butler, Christopher Millett, Naila Z Khan, Kristine Belesova, Paolo VineisObjectives
To investigate the association between drinking-water sodium concentration and blood pressure among non-pregnant women living in a high-salinity, climate-vulnerable coastal region of Bangladesh.
Design
Follow-up study of women originally enrolled in a population-based study conducted during pregnancy between 2009 and 2011.
Setting
Rural coastal subdistrict in southwest Bangladesh affected by saltwater intrusion and seasonal drinking-water insecurity.
Participants
Of 1208 women enrolled in the original study, 900 were located in 2018 and 740 non-pregnant women were re-enrolled and included in the present analysis. Eligible participants were women from the original study who were alive and still residing in the study area; women who had migrated could not be located, declined participation or were pregnant at follow-up were excluded.
Primary and secondary outcome measures
The primary outcome was blood pressure, measured using a standardised protocol. Main exposure was sodium concentration in household drinking water and reported drinking-water source. Secondary analyses assessed temporal changes in drinking-water sodium between 2009 and 2018 and associations with water source, perceived taste and changes in exposure over time.
Results
Mean sodium concentration in household drinking water was highest in groundwater/tubewell users (933 mg/L, SD 372). Approximately 22% of women consumed drinking water contributing up to 94% of the WHO-recommended maximum daily sodium intake, assuming 2 L/day consumption. Sodium concentrations increased in seven of nine administrative unions between 2009 and 2018 (p=0.013). Compared with women consuming water containing <200 mg/L sodium, exposure to >1000 mg/L was associated with higher odds of raised diastolic blood pressure (adjusted OR 2.30, 95% CI 1.40 to 3.77; p=0.001). Restricted cubic spline and piecewise regression models suggested a non-linear association, with a threshold near 1000 mg/L. No statistically significant association was observed for systolic blood pressure.
Conclusions
High sodium concentrations in drinking water were associated with elevated diastolic blood pressure among women in coastal Bangladesh. Drinking-water salinity may represent an under-recognised cardiovascular risk in climate-vulnerable coastal populations. These findings support the need for salinity surveillance, climate-resilient low-sodium drinking-water supplies and further research to inform health-based standards for sodium in drinking water.
Trial registration number
Not applicable.