- Primary objective is to observe the effect of providing salt substitute on population blood pressure in Tibet. Secondary objective is to observe the effect of such intervention on population mortality, cardiovascular mortality and life expectancy. In addition, the data collected from high-risk population (sub-group) in the study will be used in China Salt Substitute and Stroke Study (SSaSS). Also, serum cholesterol and random blood glucose of people over 60 in Tibet will be collected.