To the best of our knowledge, this study provides the first possible evidence that individuals exposed to SARS-CoV-2 infection are prone to developing cardiovascular disease in Luanda, the capital city of Angola. Generally, elevations in blood pressure values have been identified as an independent factor in the development of cardiovascular disease or end-stage renal disease. We showed that individuals exposed to SARS-CoV-2 have blood pressure levels of around 136/84 mmHg. Although it is within the accepted values as normal,15 these values were high in comparison to the average of the healthy population and not exposed to SARS-CoV-2 in Angola, which was around 131/80. These findings showed that the need for interventions to prevent cardiovascular or kidney disease should focus not only on individuals who have blood pressure above 140/90, which is globally considered high but also pay attention to individuals with normal high blood pressure values, especially those exposed to viral infectious diseases, such as the SARS-CoV-2 because they present high mean values when compared to the mean values of the population not exposed to viral infectious diseases. These results also emphasize that blood pressure quintile (I. Lowest, II. Second, III. Third, IV. Fourth, and V. Highest) definition studies in the Angolan population exposed or not to viral infectious diseases as well as the population with or without the presence of chronic diseases should be carried out in different regions, in order to assist Angolan clinicians in decision-making to prevent the progression of cases of cardiovascular or renal diseases in the population.15,16
It is worth mentioning that individuals with active or recent infection with positive IgM antibodies against SARS-CoV-2 had a mean blood pressure of around 143/90 mmHg. Furthermore, the prevalence of individuals with high blood pressure status increases significantly (6.8–40%, p = 0.005) with the presence of active or recent SARS-CoV-2 infection (Table 1). We cannot rule out the possibility that these individuals already had a history of high blood pressure before they were exposed to SARS-CoV-2.17 Despite this, these findings showed on the one hand that individuals with a previous history of high blood pressure have a higher risk of becoming infected or developing severe COVID-19, as reported by previous studies.11,18−20 Indeed, a study carried out by Wang and colleagues, showed that 58% (21/66) of patients who required admission to intensive care were patients with hypertension, compared to 22% (22/51) of hypertensive patients who did not develop COVID-19 severe (p < 0.001).18 On the other hand, our findings showed that SARS-CoV-2 infection could induce unfavorable cardiovascular clinical outcomes, starting with a significant rise in the values of the systolic pressure (from 131 ± 12.2mmHg to 143 ± 9.96mmHg, p = 0.022), diastolic pressure (from 80.0 ± 9.64mmHg to 89.8 ± 11.6mmHg, p = 0.024), and pulse (from 72.1 ± 11.0mmHg to 74.4 ± 7.86 mmHg, p = 0.637), especially in individuals with active or recent SARS-CoV-2 infection. In addition to the statistically significant relationship observed between recent SARS-CoV-2 infection and high blood pressure (p = 0.005), we also observed that the risk of an exposed individual with recent or past SARS-CoV-2 infection to developing high blood pressure is 3.2 times (95% CI: 0.85–12.1, p = 0.086), compared to the population not exposed to SARS-CoV-2. These results suggest that the clinical staff should closely monitor blood pressure indices in an individual with a recent infection or do a clinical follow-up of blood pressure in individuals exposed to SARS-CoV-2. We showed that the increase in blood pressure also implies an increase in the pulse blood pressure and as a result of the increase in the pulse blood pressure we will have reduced blood donation time (Table 1). As we expected, we observed a significant borderline (p = 0.060) between blood donation time and blood pressure status, where almost half (48%, 12/35) of individuals with high blood pressure had abnormal blood donation time compared to 30% (95/318) of blood donors with normal blood pressure, who also had abnormal donation time (results not shown). Furthermore, we showed that individuals exposed to SARS-CoV-2 might have a blood donation time 1.34 times higher (95% CI: 0.48–3.79, p = 0.578), compared to the unexposed population. Identification of individuals at high risk of developing cardiovascular disease from the analysis of the time of blood donation needs to be explored in future studies and the information generated will be crucial to immediately assist in the management of blood donors with abnormal donation time. Also, the relationship between the psychosocial status of the blood donor with changes in blood pressure and time of donation, needs to be explored in the future.
Previous studies have shown that there appears to be an association between ABO/Rh blood groups and SARS-CoV-2 infection.21–23 The observation that the population exposed to SARS-CoV-2 with blood group O did not exceed 50% (Table 2) might be in agreement with results reported by Cheng and colleagues, where they showed that blood group O was associated with reduced susceptibility to SARS infection.24 Generally, studies have shown that people with blood group O could be the least likely to be infected with SARS-CoV-2, despite being the group that most needed treatment in the hospital and artificial respiration compared to other non-O blood groups.25–28 We previously demonstrated a lower SARS-CoV-2 positivity in blood group O individuals as well as a lower risk of infection compared to non-O individuals.29 The affinity between SARS-CoV-2 with the cells of the respiratory or gut system as a function of the host's ABO/Rh blood group, is not yet clarified and is the subject of further investigation in the future. Furthermore, has no scientific evidence showing whether the blood pressure of the population exposed to SARS-CoV-2 changes according to ABO/Rh blood groups. Even though, we already expected that blood donors over 40 years of age would have the highest mean blood pressure or the pulse and the shortest donation time (Table 2), in agreement with what was described by other authors who reported an increase in blood pressure with increasing age.30,31 However, it is worth noting that advanced age (over 40 years) has previously been described as an independent risk factor for SARS-CoV-2 infection and severity, even in Angola, as shown by our research team.4,29,32 In addition, this study reports that adults over 40 years of age are more likely to contract viral infectious diseases and also have a high chance of developing high blood pressure with potential risk for an unfavorable cardiovascular or renal clinical outcome. In terms of ABO/Rh blood groups, it is worth mentioning at the first stage that different from the Rh + factor that represented over 50% of the Angola population, the blood group O despite being the most prevalent, no longer represents more than 50% of the population (Table 2). This differs from the prevalence described in a study carried out in 1973 by Spielmann and colleagues, where blood group O represented between 54 to 59% of the Angolan population,33 suggestings a decrease of blood group O in the population over the years. Indeed, a recent study carried out by our research team, showed a significant increase in non-O blood groups, with special attention to blood group B,29 which, in addition to increasing its prevalence, has been associated with the risk of arterial hypertension in the Angolan population.34,35
Table 2
Biological factors linked to the blood pressure pattern among exposure subjects to SARS-CoV-2 in Luanda, Angola
Independent variables
|
Gender
|
Age group
|
ABO blood group
|
Rh blood type
|
|
Male (%)
|
≤ 40 yrs (%)
|
> 40 yrs (%)
|
p-value
|
Non-O (%)
|
O (%)
|
p-value
|
Rh- (%)
|
Rh+ (%)
|
p-value
|
Overall
|
16 (100)
|
14 (87.5)
|
2 (12.5)
|
|
9 (56.3)
|
7 (43.8)
|
|
1 (6.30)
|
15 (93.8)
|
|
Blood pressure, mmHg
|
|
|
|
|
|
|
|
|
|
|
SBP, Mean ± SD
|
136 ± 14.2
|
135 ± 14.6
|
139 ± 14.9
|
0.775
|
137 ± 12.3
|
134 ± 17.2
|
0.714
|
150 ± 0.00
|
135 ± 14.1
|
0.313
|
DBP, Mean ± SD
|
84.2 ± 12.7
|
83.7 ± 13.5
|
87.5 ± 2.12
|
0.707
|
85.7 ± 13.1
|
82.3 ± 12.8
|
0.614
|
100 ± 0.00
|
83.1 ± 12.4
|
0.208
|
Distribution
|
|
|
|
|
|
|
|
|
|
|
Normal (≤ 140/90)
|
13 (81.3)
|
11 (78.6)
|
2 (100)
|
0.468
|
7 (77.8)
|
6 (85.7)
|
0.687
|
0 (0.00)
|
13 (86.7)
|
0.032
|
Abnormal (> 140/90)
|
3 (18.8)
|
3 (21.4)
|
0 (0.00)
|
|
2 (2.22)
|
1 (14.3)
|
|
1 (100)
|
2 (13.3)
|
|
Pulse pressure, BPM
|
|
|
|
|
|
|
|
|
|
|
Mean ± SD
|
73.7 ± 8.50
|
72.8 ± 8.66
|
80.0 ± 4.24
|
0.276
|
75.3 ± 9.07
|
71.6 ± 7.85
|
0.398
|
65.0 ± 0.00
|
74.3 ± 8.46
|
0.307
|
Distribution
|
|
|
|
|
|
|
|
|
|
|
Normal (60–100)
|
16 (100)
|
14 (100)
|
2 (100)
|
Undefined
|
9 (100)
|
7 (100)
|
Undefined
|
1 (100)
|
15 (100)
|
Undefined
|
Abnormal (< 60 or > 100)
|
0 (0.00)
|
0 (0.00)
|
0 (0.00)
|
|
0 (0.00)
|
0 (0.00)
|
|
0 (0.00)
|
0 (0.00)
|
|
Donation duration, minutes
|
|
|
|
|
|
|
|
|
|
|
Mean ± SD
|
5.48 ± 1.61
|
5.58 ± 1.70
|
4.78 ± 4.60
|
0.530
|
5.43 ± 1.50
|
5.53 ± 1.87
|
0.904
|
6.00 ± 0.00
|
5.44 ± 1.66
|
0.749
|
Distribution
|
|
|
|
|
|
|
|
|
|
|
Normal (5–10)
|
10 (62.5)
|
9 (64.3)
|
1 (50.0)
|
0.696
|
5 (55.6)
|
5 (71.4)
|
0.515
|
1 (100)
|
9 (60.0)
|
0.424
|
Abnormal (< 5 or > 10)
|
6 (37.5)
|
5 (35.7)
|
1 (50.0)
|
|
4 (44.4)
|
2 (28.6)
|
|
0 (0.00)
|
6 (40.0)
|
|
Notes: Past infection (IgG+/IgM-) and Recent infection (IgG-/IgM + or IgG+/IgM+); SBP: Systolic blood pressure; DBP: Diastolic blood pressure; BPM: Beats per minute |
The bold number was statistically significant in the Chi-square test (X2) or independent-sample T-tests (p < 0.05). |
There are important limitations to be considered when interpreting the results of this study. Firstly, the small sample size of individuals exposed to SARS-CoV-2 limits our power to analyze and extrapolate the results to the whole population of Luanda, the capital city of Angola. Secondly, the effect of blood pressure changes was not taken into account for the different SARS-CoV-2 strains, which also deserves investigation in the future. Third, information about blood pressure changes during or after at least six months since SARS-CoV-2 exposure was not considered in this study and this should also be considered in future studies. Fourth, more sociodemographic (e.g. area of residence, occupation, educational level, and monthly income), behavioral (e.g. alcoholism, tobacco, and physical activities), and clinical (e.g. family history of chronic illness) information, were not investigated in this study. Therefore, future studies of this nature should also consider the possibility of including these variables that have considerable weight from the point of view of epidemiology and dissemination of infectious agents. Finally, the clinical outcome of individuals exposed to SARS-CoV-2 and who had high blood pressure was not recorded. As we can see, as the COVID-19 pandemic takes hold, with countless variants emerging, numerous research questions remain open, to which we draw the attention of the scientific community for the assessment of the impact of SARS-CoV-2 infection on the course or long term in populations from different settings, mainly in LMICs.2,12 These results must be considered very preliminary, despite showing a possible influence of biological factors such as age, gender, and AB/Rh blood group in blood pressure indices among individuals with recent or past infection by SARS-CoV-2 in Angola, which could help to give a new direction to the management of individuals exposed to SARS-CoV-2 in Angola.