3. Explore a statistical formula to estimate 24-h USE by multi-time spot urine. The study plan to enroll 200 children and 200 adults to collect a whole 24-h urine spot by spot continuously. After a laboratory examination of sodium concentration from both spot urine samples and 24-h urine sample, the exploratory estimation using multi-spot urine to assess 24-h urinary sodium excretion will analyzed statistically. The validation for the estimation method will be conducted in Chinese population as well.