Participant enrolment flow diagram is shown in the additional file 2.
Table 1
Relationship between hypertension and demographic and clinical characteristics of the study population
| Hypertensive n, 43 median (IQR) | Normotensive n, 42 median (IQR) | p-value |
Age (years) | 40 (38, 42) | 40 (38, 41) | 0.389 |
Sex, n(%) | | | |
Male | 20 (46.5) | 18 (42.9) | 0.735 |
Female | 23 (53.5) | 24 (57.1) | |
HIV Status, n(%) | | | |
Positive | 22 (51.2) | 21 (50.0) | 0.915 |
Negative | 21 (48.8) | 21 (50.0) | |
Body mass index, kg/m2 | 25.6 (23.1, 30.0) | 17.6 (16.9, 19.6) | < 0.001 |
Fasting blood glucose, mmol/l | 5.4 (5.0, 6.2) | 4.9 (4.5, 5.6) | 0.038 |
Cholesterol, mmol/l | 4.1 (3.1, 4.6) | 3.6 92.0, 4.2) | 0.626 |
High density lipoprotein, mmol/l | 1.2 (1.1, 1.8) | 1.4 (1.0, 1.5) | 0.633 |
Low density lipoprotein, mmol/l | 2.0 (1.4, 2.9) | 1.5 (1.2, 2.1) | 0.789 |
Triglycerides, mmol/l | 1.0 (1.0, 2.0) | 1.0 (1.0, 1.5) | 0.680 |
Platelets, x 109/L | 232 (193, 327) | 261 (195, 290) | 0.562 |
Neutrophils, x109cell/L | 2.7 (2.1, 3.5) | 2.0 (1.6, 3.7) | 0.060 |
Lymphocytes, x109cell/L | 2.1 (1.5, 2.5) | 1.9 (1.4, 2.2) | 0.343 |
Monocytes, x109cell/L | 0.56 (0.39, 0.72) | 0.34 (0.25, 0.45) | 0.001 |
IQR, interquartile range |
The study consisted of 45% (n, 38) males and 55% (n, 47) females. 43 of the study population were hypertensive and HIV positive. The youngest was 29 and the oldest was 49 years old with the median age of 38 years. There was no significant difference in age, sex, HIV status and lipid profile distribution between hypertensives and normotensives in the study population. While platelet, neutrophil and lymphocyte count were similar in both, hypertensives had elevated FBG, BMI and monocyte count when compared with normotensives (Table 1).
In multivariate logistic regression (Table 2), age, sex, BMI, HIV status, FBG, IL-6, tumor necrosis factor-alpha (TNF-α) remained significantly associated with hypertension, p < 0.05. The HIV positive had a 3% reduced risk of developing hypertension compared to the normotensive individuals (0.02, 0.50, 95% CI, p = 0.014).
Serum levels of pro- and anti-inflammatory cytokines were also compared between hypertensives and normotensives and it was found that IL-6, TNF-α and IL-17A were elevated among hypertensives, p < 0.01 (Fig. 1; see also Additional file 2).
Figure 1. Pro- and anti-inflammatory cytokine plasma levels in hypertensive and normotensive individuals. IL-6, tumor necrosis factor alpha and IL-17A were elevated in hypertension. HTN, Hypertensive; NT, normotensive. ***p < 0.001, **p < 0.01
Pro- and anti-inflammatory cytokines were compared between the last day of low- and high-salt diets to compare the effect of high dietary salt on inflammatory markers (Additional file 2). IL-2 was higher (p = 0.013) while IL-10 was lower (p = 0.042) in the normotensive group compared to the hypertensive group (high salt minus low salt cytokine concentration). IL-21 was lower in the hypertensive group compared with the normotensive in the high salt.
Table 2
Association between hypertension and clinical characteristics in logistic regression
Variable | Unadjusted Odds Ratio OR (95%CI) | p-value | Adjusted Odds Ratio AOR (95%CI) | p-value |
Age (years) | 1.1 (0.9, 1.2) | 0.364 | 1.3 (1.0, 1.7) | 0.043 |
Sex, n(%) | | | | |
Female | 1 | | 1 | |
Male | 1.2 (0.5, 2.7) | 0.735 | 7.6 (1.3, 46.0) | 0.026 |
HIV Status, n(%) | | | | |
Negative | 1 | | 1 | |
Positive | 1.0 (0.4, 2.4) | 0.915 | 0.03 (0.02, 0.50) | 0.014 |
Body mass index, kg/m2 | 1.3 (1.1, 1.5) | < 0.001 | 1.3 (1.0, 1.6) | 0.016 |
Fasting blood glucose, mmol/l | 1.7 (1.0, 2.8) | 0.037 | 10.7 (2.0, 58.3) | 0.006 |
Monocytes, x109cell/L | 38.7 (3.5, 69.3) | 0.003 | 13 (0.27, 69.0) | 0.193 |
IL-6, pg/ml | 2.3 (1.5, 3.5) | < 0.001 | 4.3 (1.8, 10.0) | 0.001 |
Tumor necrosis factor-alpha, pg/ml | 1.4 (1.1, 1.8) | 0.006 | 1.9 (1.2, 3.0) | 0.007 |
IL-17A, pg/ml | 1.9 (1.2, 2.9) | 0.004 | 2.1 (0.9, 4.7) | 0.065 |
P-value less than 0.05 are in bold |