Vascular Reactivity and Salt Sensitivity in Normotensive and Hypertensive Adult Nigerians

Abstract

There are not many studies designed to study the relationship between vascular reactivity and salt sensitivity in a black population. Fifty-two hypertensive (HT) and forty-seven age-matched normotensive (NT) Nigerian subjects took part in the study after informed consent was obtained from them. Ethical clearance was obtained from the College of Medicine of the University of Lagos. Vascular hyperreactivity in response to the Cold Pressor Test (CPT) was determined as a change in systolic blood pressure (ΔSBP) or diastolic blood pressure (ΔDBP) ≥ +15mmHg. This was determined before and after salt-loading with 200mmol Na⁺/day for 5 days. Salt sensitivty was determined as a change in mean arterial blood pressure (ΔMABP) ≥+5mmHg. Salt-loading led to significant increases in SBP among NT (p = 0.03) and among HT (p = 0.0001) subjects; DBP increased significantly only among HT subjects (p = 0.0003). Systolic and diastolic hyperreactivity were higher among HT (49% and 39% respectively) compared to NT (44% and 39% respectively) at baseline. However systolic hyperreactivity (SHP) increased from 44% to 64% after salt-loading among the NT while diastolic hyperreactivity (DHP) reduced from 39% to 36%. Among the HT, both SHP and DHP reduced from 49% to 33% and from 41% to 31% respectively following salt-loading. Salt sensitivity was higher among HT (56%) compared to NT 34%. Salt sensitivity was positively correlated with systolic reactivity before salt (r = 0.33; p < 0.05) and after salt (r = 0.25; p > 0.05) but negatively correlated with diastolic reactivity before salt (r = -0.38; p < 0.05) and after salt (r = -0.40; p < 0.05) among NT. These results suggest that systolic hyperreactivity may be a significant determinant in the development of salt sensitive hypertension among this population.

Keywords: Vascular reactivity, Salt sensitivity hypertension, Blood pressure