Population-based cohorts are essential to monitor the health status of the population, assess the disease burden, further our understanding of the determinants of health, whether social, economic, environmental, related to lifestyle or molecular. Prospectively collected longitudinal health data are key to provide insight into the natural history and the early determinants of diseases. Large scale cohorts conducted in other countries, and hence other socio-economic settings and health care systems, do not provide information on the exposure of the Swiss population.