Higher education and income are related to a better Na:K ratio in blacks: Baseline results of the treatment of mild hypertension study (TOMHS) data

In the United States, blacks have higher rates of hypertension than whites. A possible contributing factor to this higher rate of hypertension could be dietary differences between blacks and whites relating to sodium and potassium intake, which in turn could be related to socioeconomic differences between blacks and whites. Baseline data from the Treatment of Mild Hypertension Study (TOMHS) was used to assess differences in the urinary excretion of sodium and potassium, and the Na:K ratio between black and white participants, and also to explore the relationship of socioeconomic status (SES) and urinary electrolyte excretion within each ethnic group. Participants were men and women ages 45 to 69 with stage I diastolic hypertension (DBP ≤ 99 mm Hg). Level of education and annual household income were used as indicators of SES. Two overnight urine samples were collected and analyzed for Na and K at entry on 172 black and 710 white participants. Blacks had a significantly higher mean Na:K ratio than whites, 4.3 v 3.6 (P < .001). This was primarily due to higher urinary Na excretion in blacks than whites, 57.8 v 52.7 mmol/8 h (P = .05). Analysis by education and income level showed that higher levels of urinary Na and Na:K in blacks than whites was restricted to those with lower education and income levels. For higher education and income levels, blacks had slightly lower levels of urinary Na and Na:K than whites. Correspondingly, education and income levels were related to urinary Na and Na:K in blacks but not in whites. This suggests that lower SES blacks could benefit from interventions to reduce dietary Na and increase dietary K, which would decrease their urinary Na:K ratio and may make them less prone to developing hypertension.