Sodium sensitivity, growth and family history of hypertension in young blacks

The response to chronic oral sodium loading was studied in young adult (18-23 years) blacks. A representative sample of participants (n=40) from previous longitudinal studies had growth measures at age 6-7 years and 11-16 years. Blood pressure, weight and stress-induced reactivity were measured before and after 14 days of 10 g NaCl daily added to the usual diet. A sodium-sensitive response (SS) was an increase in mean arterial pressure (MAP) greater than or equal to 5 mmHg. A sodium-insensitive response (S) was an increase in MAP less than or equal to 5 mmHg. Family history of hypertension (FH+) was determined by self-report. Fifty-three per cent were SS. There were no difference in age-related BP, weight or height between SS and SI in childhood or adolescence. Those with a family history of hypertension had a greater BP response to stress and greater weight change with sodium load. The group which was both SS and FH+ had the highest weight and MAP stress response after sodium load. These results indicate that sodium sensitivity is high among blacks, but does not correlate with childhood growth variables. Sodium sensitivity and FH+ combined produce the greatest stress-induced BP response.