PhD project: Geographical variation in incidence of heart diseases and association with magnesium and sodium in drinking water

Cardiovascular disease is a major cause of death and disability worldwide with severe consequences for both individuals and society. Studies indicate that individual-level risk factors only explain 50% of the incidence in cardiovascular disease (4). However, investigating the neighborhood determinants (ex. Environmental exposures) of the geographical patterns in heart diseases might increase our understanding of the disease etiology and thereby can improve the existing prevention strategies.

The project focuses on atrial fibrillation and hypertension, since both are risk factors for more severe cardiovascular diseases such as stroke and heart failure and predictions estimate a doubling of the number of individuals aged ≥55
years living with AF by 2060.

Drinking water components are possible neighborhood exposures for cardiovascular diseases, and variations in ex. magnesium, sodium and water hardness might explain part of the geographical variations in heart diseases in Denmark.


The aim of the project is to study association between the risk factors atrial fibrillation and hypertension and magnesium and sodium in drinking water in Denmark. Within the project, geographical variations in both atrial fibrillation and magnesium, sodium, calcium and potassium in drinking water are analyzed. Furthermore, both association between increased sodium level in drinking water and incidence of stroke and heart failure acute myocardial infarct among adults with hypertension and the association between magnesium in drinking water and incidence of atrial fibrillation among adults are studied.

Provided that an association between water exposure and atrial fibrillation and/or hypertension exists, this study can contribute to our understanding of the disease etiology and this study can contribute to the health discussion about drinking water softening, since some water softening methods result in a reduction of Mg and an increase in Na in drinking water.


It is a register based cohort study, where outcome is geocoded individual-level data on atrial fibrillation, hypertension, stroke and acute myocardial infarct. Exposure data is concentrations of sodium, potassium, magnesium and calcium aggregated for each water supply area in Denmark.
Spatial scan statistics are used for analyzing geographical variations in atrial fibrillation and selected drinking water elements.
Spatial Poisson regression analysis of incidence rates will be performed to estimate the incidence rate ratios of sodium and magnesium exposure in quantiles, for the association between sodium and adults with hypertension and magnesium and adults with atrial fibrillation, respectively. 

Project period



Karen Elise Jensen Fonden og GEUS.

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