Association between calcium and magnesium content of tap water
and CVD mortality in Switzerland

The impact of calcium and magnesium from tap water on mortality risk has recently been challenged in that the resulting association merely might be a consequence of poor study design. A general weakness of studies examining the relationship between tap water consumption and disease outcomes is the lack of environmental factors that are often associated with tap water composition. For example, in Switzerland, living at higher altitude is associated with lower risk of ischemic heart disease (IHD). However, this association is partially due to steeper terrain slope, lower air pollution and traffic noise and more favorable climatic conditions compared to low-land regions. Existing studies on tap water consumption and cardiovascular outcomes were unable to adequately consider these potential confounders in the analysis. Moreover, previous studies relied on study samples with inherent selection bias. Switzerland is an ideal setting for the examination of this research question. Due to the different geological properties of the bedrock, this country combines substantial variations in tap water composition. The aims of this projects are 1. To gather detailed information on calcium and magnesium content of tap water on community level in Switzerland and to complement this with data on regional bedrock property 2. To evaluate significance, magnitude and shape of the association between calcium and magnesium content of tap water and stroke / IHD 3. To disentangle the impact of environmental factors (e.g. altitude, slope, geographical aspect, climate (annual means), air pollution and green space) on the above mentioned association