Who is most at risk for salt sensitivity?

African Americans.

http://www.medscape.com/viewarticle/407741_3

There are five broad categories consistently associated with salt sensitivity. These include demographic factors, racial and social factors, renal function factors, hormonal factors, and dietary habit factors (Table II).

There is a direct, positive relationship between age and salt sensitivity, with increasing salt sensitivity noted in older subjects. While salt sensitivity is usually perceived as a phenomenon occurring in mid-life or later (i.e., after age 45), it has also been documented in Caucasian adolescents who are overweight.[17-19] Weight may also be responsible for the gender differences noted in blood pressure response to sodium. Women are usually found to be more salt-sensitive than men. However, as Weinberger[9] noted, all studies examining salt sensitivity administered the same amount of sodium to both men and women. Women typically weigh less than men and, therefore, may have been subjected to a greater salt load based on body weight, making it more likely that a blood pressure response would be noted in women. However, most studies have shown that regardless of sodium intake and the presence or absence of hypertension, salt-sensitive subjects tend to weigh more than salt-resistant subjects.[20] In addition, weight reduction in white adolescents eliminated the sensitivity of blood pressure to sodium.[17]

Salt sensitivity has been found to be more prevalent in young, old, normotensive, and hypertensive African Americans than Caucasians.[13,14,21,22] The increased prevalence of salt sensitivity in African Americans has been demonstrated in studies using i.v. NaCl loading as well as in studies using dietary sodium designs.[10,12,14] The finding of salt sensitivity is so prevalent that it is considered to be a "hallmark" of black hypertension, as salt sensitivity is found in 73% of all African American hypertensive patients.[23]