Those studies are usually not very good. They often fail to recognize that people who are on a low-sodium diet are very sick, for example (just like those studies that say that a low BMI is very dangerous but fail to control for the fact that very ill people are thin). I just think it would be really strange if humans had such a high need for salt, because until a few hundred years ago people did not add salt to their diet, getting only the naturally occurring sodium from food, and people did just fine.

According to Harvard School of Public Health, salt sensitivity is a myth: http://www.hsph.harvard.edu/nutritionsource/salt-questions/#...