Blood Pressure and Arterial Stiffness in Kenyan Adolescents With the Sickle Cell Trait

Ambulatory blood pressure monitoring in pediatric patients with sickle cell anemia

INTRODUCTION

Sickle cell anemia (SCA) is a hemoglobinopathy presenting severe endothelial damage associated with increased prevalence of hypertension (HTN). Few studies have used ambulatory blood pressure monitoring (ABPM) in pediatric patients with SCA. The aim of this study was to characterize the ABPM profile in children with SCA.

METHODS

A retrospective cross-sectional study was conducted on all subjects <18 years of age with SCA who presented at a medical reference center in the city of Cartagena, Colombia. Anthropometric, clinical laboratory, treatment, and ABPM parameters, including ambulatory arterial stiffness index (AASI) were registered.

RESULTS

The study included 79 patients, of these, 23 (29%) children had normal BP, 49 (62%) had abnormal BP and 7 (9%) had HTN. Mean age was 10.5 ± 3.6 years and 44 (56%) cases were male. Forty-eight (60%) patients had pre-HTN. Masked HTN was present in 6 (8%) patients. One (1%) had ambulatory HTN, and another one (1%) had white coat HTN. The HTA group exhibited significantly higher systolic BP and diastolic BP compared to the other groups in 24-hour BP readings, daytime BP, and night-time BP ABPM parameters ( P  < 0.05), except for daytime DBP ( P  = 0.08). Mean AASI was 0.4 ± 0.2. The HTN group had the highest AASI value compared to the other groups ( P = 0.006).

CONCLUSION

Significant alterations in ABPM parameters are frequently observed in pediatric patients with SCA. The incorporation of ABPM, along with the assessment of AASI, is recommended for a comprehensive evaluation of cardiovascular and renal risk in SCA patients.

Hypertension among adolescents in sub-Saharan Africa: a systematic review

Introduction

Hypertension (HTN) among adolescents is common in high-income countries, and leads to increased premature cardiovascular diseases (CVD). In sub-Saharan Africa (SSA), the prevalence of HTN among adolescents, associated risk factors and CVD complications are not well-described. Such data is needed for planning public health programs to prevent premature CVD in SSA.

Methods

We systematically searched 5 databases (MEDLINE, Embase, Google Scholar, Web of Science, and African Index Medicus) from their establishment to December 2021. Key search terms were: adolescent, arterial hypertension, and names of the 48 countries in SSA. We used Covidence® to manage the search results. The review was registered in the Open Science Framework (OSF) https://osf.io/p5sbt/.

Results

We identified 4,008 articles out of which we screened 3,088 abstracts, and reviewed 583 full-text articles. We finally included 92 articles that were published between 1968 to December 2021. The majority were cross-sectional studies (80%) and conducted in school settings (78%). The risk of bias was low for 59 studies (64.1%), moderate for 29 studies (31.5%), and high for 4 studies (4.3%). Overall, the prevalence of HTN varied widely from 0.18% to 34.0% with a median (IQR) of 5.5% (3.1%, 11.1%). It was relatively higher in studies using automated blood pressure (BP) devices, and in studies defining HTN using thresholds based on percentile BP distribution for one's height, age, and sex. In addition, the prevalence of HTN was significantly higher in studies from Southern Africa region of SSA and positively correlated with the year of publication. Across studies, traditional risk factors such as age, sex, body mass index, and physical inactivity, were commonly found to be associated with HTN. In contrast, non-traditional risk factors related to poverty and tropical diseases were rarely assessed. Only three studies investigated the CVD complications related to HTN in the study population.

Conclusion

The prevalence of HTN among adolescents in SSA is high indicating that this is a major health problem. Data on non-traditional risk factors and complications are scarce. Longitudinal studies are needed to clearly define the rates, causes, and complications of HTN.

Systematic Review Registration

https://osf.io/p5sbt/, identifier (10.17605/OSF.IO/P5SBT).

Elevated blood pressure among adolescents in sub-Saharan Africa: a systematic review and meta-analysis

BACKGROUND

More people from sub-Saharan Africa aged between 20 years and 60 years are affected by end-organ damage due to underlying hypertension than people in high-income countries. However, there is a paucity of data on the pattern of elevated blood pressure among adolescents aged 10-19 years in sub-Saharan Africa. We aimed to provide pooled estimates of high blood pressure prevalence and mean levels in adolescents aged 10-19 years across sub-Saharan Africa.

METHODS

In this systematic review and meta-analysis, we searched PubMed, Google Scholar, African Index Medicus, and Embase to identify studies published from Jan 1, 2010, to Dec 31, 2021. To be included, primary studies had to be observational studies of adolescents aged 10-19 years residing in sub-Saharan African countries reporting the pooled prevalence of elevated blood pressure or with enough data to compute these estimates. We excluded studies on non-systemic hypertension, in African people not living in sub-Saharan Africa, with participant selection based on the presence of hypertension, and with adult cohorts in which we could not disaggregate data for adolescents. We independently extracted relevant data from individual studies using a standard data extraction form. We used a random-effects model to estimate the pooled prevalence of elevated blood pressure and mean systolic blood pressure (SBP) and diastolic blood pressure (DBP) levels overall and on a sex-specific basis. This study is registered with PROSPERO (CRD42022297948).

FINDINGS

We identified 2559 studies, and assessed 81 full-text studies for eligibility, of which 36 studies comprising 37 926 participants aged 10-19 years from ten (20%) of 49 sub-Saharan African countries were eligible. A pooled sample of 29 696 adolescents informed meta-analyses of elevated blood pressure and 27 155 adolescents informed meta-analyses of mean blood pressure. Sex data were available from 26 818 adolescents (14 369 [53·6%] were female and 12 449 [46·4%] were male) for the prevalence of elevated blood pressure and 23 777 adolescents (12 864 [54·1%] were female and 10 913 [45·9%] were male) for mean blood pressure. Study quality was high, with no low-quality studies. The reported prevalence of elevated blood pressure ranged from 4 (0·2%) of 1727 to 1755 (25·1%) of 6980 (pooled prevalence 9·9%, 95% CI 7·3-12·5; I?=99·2%, p_{heterogeneity}<0·0001). Mean SBP was 111 mm Hg (95% CI 108-114) and mean DBP was 68 mm Hg (66-70). 13·4% (95% CI 12·9-13·9; p_{heterogeneity}<0·0001) of male participants had elevated blood pressure compared with 11·9% (11·3-12·4; p_{heterogeneity}<0·0001) of female participants (odds ratio 1·04, 95% CI 0·81-1·34; p_{heterogeneity}<0·0001).

INTERPRETATION

To our knowledge, this systematic review and meta-analysis is the first systematic synthesis of blood pressure data specifically derived from adolescents in sub-Saharan Africa. Although many low-income countries were not represented in our study, our findings suggest that approximately one in ten adolescents have elevated blood pressure across sub-Saharan Africa. Accordingly, there is an urgent need to improve preventive heart-health programmes in the region.

FUNDING

None.

Evolutionary trilogy of malaria, angiotensin II and hypertension: deeper insights and the way forward

Despite clinical and pathological distinctions between malaria and hypertension, accumulated epidemiological and evolutionary evidence indicate the need of deeper understanding how severe malaria contributes to elevated hypertension risk. Malaria is said to exert strong selection pressure on the host genome, thus selecting certain genetic polymorphisms. Few candidate polymorphisms have also been reported in the RAS (ACE I/D and ACE2 rs2106809) that are shown to increase angiotensin II (ang II) levels in a combinatorial manner. The raised ang II has some antiplasmodial actions in addition to protecting against severe/cerebral malaria. It is hypothesized that RAS polymorphisms may have been naturally selected over time in the malaria-endemic areas in such a way that hypertension, or the risk thereof, is higher in such areas as compared to non-malaria endemic areas. The purpose of this review is to gain deeper insights into various sparse evidence linking malaria and hypertension and suggesting a way forward.

Sustained high blood pressure and 24-h ambulatory blood pressure monitoring in Tanzanian adolescents

Estimates for prevalence of high blood pressure (BP) among adolescents in Africa vary widely and few studies, if any, have documented the results of the recommended stepwise BP screening. In this cross-sectional study in Tanzania, we aimed to estimate prevalence of sustained high BP in 3 public secondary schools using the American Academy of Pediatrics BP screening strategy. On Day 1, one screening automated office BP (AOBP) measurement (Step 1) was followed by two more AOBP measurements (Step 2). Repeat AOBP measurements were obtained after about one month on adolescents with high AOBP measurements on Day 1 (Step 3). Participants with sustained high BP underwent 24-h ambulatory BP monitoring (step 4). Of all 500 enrolled participants, the prevalence of high blood pressure at each step in the process was 36.6% (183), 25.6% (128), 10.2% (51), and 2.6%(13) respectively for Steps 1-4. All except 6 students completed all 4 steps of the BP screening algorithm as indicated. We conclude that diagnosis of hypertension in African adolescents should use multiple AOBP measurements over multiple days followed by 24-h ABPM. Screening for high BP in school settings appears to be feasible and could provide a platform for cardiovascular disease education and health promotion.

Malaria is a cause of iron deficiency in African children

Malaria and iron deficiency (ID) are common and interrelated public health problems in African children. Observational data suggest that interrupting malaria transmission reduces the prevalence of ID1. To test the hypothesis that malaria might cause ID, we used sickle cell trait (HbAS, rs334 ), a genetic variant that confers specific protection against malaria2, as an instrumental variable in Mendelian randomization analyses. HbAS was associated with a 30% reduction in ID among children living in malaria-endemic countries in Africa (n = 7,453), but not among individuals living in malaria-free areas (n = 3,818). Genetically predicted malaria risk was associated with an odds ratio of 2.65 for ID per unit increase in the log incidence rate of malaria. This suggests that an intervention that halves the risk of malaria episodes would reduce the prevalence of ID in African children by 49%.

Effects of -3.7α Deletion and Sickle-Cell Trait on Ventilatory and Hemodynamic Responses to Maximum Exercise in Young Saudi Females

Introduction

Hemoglobinopathies are common disorders in Saudi Arabia and have an impact on the general health of the affected individuals. The current study aimed to find out the effects of the presence of α 3.7 kb rightward deletion or sickle-cell trait (SCT) on ventilatory and hemodynamic parameters of maximum exercise testing in young Saudi women.

Methods

In a cross-sectional study, 75 randomly selected female students from different colleges were tested for VO_2max using a COSMED system for maximum exercise testing. Blood parameters and globin genotyping were determined.

Results

Hemoglobin genetic studies revealed 28 of the students had 3.7 α-globin deletion only (^−3.7α₂/α₁α₂), five had SCT, and 42 had normal α-globin (α₁α₂/α₁α₂ and no HbS) and were considered the control group. Subjects with ^−3.7α₂/α₁α₂ showed significantly lower VO_2max and higher resting systolic blood pressure, while SCT carriers showed no difference in regard to ventilatory parameters, but had higher post-exercise systolic blood pressure than controls.

Conclusion

It is concluded that individuals with 3.7 α-globin deletion might have lower fitness capacity, as demonstrated by lower VO_2max, which might explain the general lower VO_2max in the young women of this population. Furthermore, increments in resting systolic and posteexercise systolic blood pressure in 3.7 α-globin deletion and SCT, respectively, might indicate a future risk of cardiovascular diseases and require attention and extensive studies.

Unmasking hypertension in children and adolescents with sickle/beta-thalassemia

Sickle cell disease (SCD) is associated with increased risk of cardiovascular disease, although blood pressure (BP) levels have been reported to be lower in SCD patients compared to general population. Aims of the present study were to investigate the prevalence of BP phenotypes and levels of arterial stiffness in pediatric patients with SCD and to assess the differences with children at risk for hypertension. We included in the study 16 pediatric SCD (HbS/β-thalassemia, S/β-thal) patients and 16 consecutive children at risk for hypertension referred to our hypertension clinic that served as high-risk controls. All patients underwent ambulatory BP monitoring and measurement of carotid-femoral pulse wave velocity (PWV). S/β-thal patients had lower office systolic BP than the high-risk control group (115.43 ± 10.03 vs 123.37 ± 11.92, P = .05) but presented similar levels of day and night ambulatory BP. Office hypertension was found in 12.5% of the S/β-thal patients and in 43.8% of the high-risk controls (P = .06), while 18.8% of the S/β-thal patients and 25% of the high-risk controls presented hypertension by ambulatory BP levels (P = .21). All of the S/β-thal patients with ambulatory hypertension had night hypertension (one combined night and day hypertension) with office normotension (masked hypertension). S/β-thal patients and high-risk controls presented equal prevalence of masked hypertension (18.8%). Children and adolescents with S/β-thal present similar prevalence of BP phenotypes and levels of PWV with children at risk for hypertension. A significant number of children and adolescents with S/β-thal may have masked nighttime hypertension despite normal office BP levels.

Epidemiological links between malaria parasitaemia and hypertension: findings from a population-based survey in rural Côte d'Ivoire

Background:

Although potential links between malaria parasitaemia and hypertension have been hypothesized, there is paucity of epidemiologic evidence on this link. We investigated in a population-based survey, the association between malaria parasitaemia and hypertension in Ivorian adults.

Methods:

We estimated the adjusted odds ratios (OR) and 95% confidence intervals (CI) of hypertension in relation to malaria parasitaemia using multinomial regression, in 997 randomly selected adults in the ‘Côte d’Ivoire Dual Burden of Disease Study’ (CoDuBu), in south-central Côte d’Ivoire. We defined malaria parasitaemia as a positive rapid diagnostic test or identification of Plasmodium spp. on microscopy. Using the mean of the last two of three blood pressure (BP) measurements and questionnaire data, we defined hypertension as SBP at least 140 mmHg or DBP at least 90 mmHg or clinician-diagnosed hypertension.

Results:

Prevalence of malaria parasitaemia and hypertension were 10 and 22%, respectively. Malaria parasitaemia was negatively associated with hypertension in participants with body temperature 36.5 °C or less [OR 0.23 (95% CI 0.06–0.84)]. Contrastingly, microscopic malaria parasitaemia showed positive associations with hypertension in participants with elevated body temperature [>36.5 °C; OR: 2.93 (95% CI 0.94–9.14)]. Participants having microscopic malaria parasitaemia with elevated body temperature had three-fold higher odds of hypertension [OR: 3.37 (95% CI 1.12–10.0)] than malaria parasitaemia-negatives with lower body temperature.

Conclusion:

Malaria parasitaemia and hypertension are prevalent and seemingly linked comorbidities in African settings. This link may depend on malaria parasitaemia symptomaticity/latency where individuals with more latent/asymptomatic malaria parasitaemia have lower risk of hypertension and those with more acute/symptomatic malaria parasitaemia have a tendency toward higher BP. The cross-sectional nature of the study limited the distinction of short-term BP elevation (interim pathophysiological stress) from hypertension development. Future longitudinal studies considering malaria/hypertension phenotypes and host molecular variations are needed to clarify involved biological mechanisms, toward comorbidity management.

Ultrasound Detection of Abnormal Cerebrovascular Morphology in a Mouse Model of Sickle Cell Disease Based on Wave Reflection

Sickle cell disease (SCD) is associated with a high risk of stroke, and affected individuals often have focal brain lesions termed silent cerebral infarcts. The mechanisms leading to these types of injuries are at present poorly understood. Our group has recently demonstrated a non-invasive measurement of cerebrovascular impedance and wave reflection in mice using high-frequency ultrasound in the common carotid artery. To better understand the pathophysiology in SCD, we used this approach in combination with micro-computed tomography to investigate changes in cerebrovascular morphology in the Townes mouse model of SCD. Relative to controls, the SCD mice demonstrated the following: (i) increased carotid artery diameter, blood flow and vessel wall thickness; (ii) elevated pulse wave velocity; (iii) increased reflection coefficient; and (iv) an increase in the total number of vessel segments in the brain. This study highlights the potential for wave reflection to aid the non-invasive clinical assessment of vascular pathology in SCD.

Effect of Previous Exposure to Malaria on Blood Pressure in Kilifi, Kenya: A Mendelian Randomization Study

Background Malaria exposure in childhood may contribute to high blood pressure ( BP ) in adults. We used sickle cell trait ( SCT ) and α+thalassemia, genetic variants conferring partial protection against malaria, as tools to test this hypothesis. Methods and Results Study sites were Kilifi, Kenya, which has malaria transmission, and Nairobi, Kenya, and Jackson, Mississippi, where there is no malaria transmission. The primary outcome was 24-hour systolic BP. Prevalent hypertension, diagnosed using European Society of Hypertension thresholds was a secondary outcome. We performed regression analyses adjusting for age, sex, and estimated glomerular filtration rate. We studied 1127 participants in Kilifi, 516 in Nairobi, and 651 in Jackson. SCT frequency was 21% in Kilifi, 16% in Nairobi, and 9% in Jackson. SCT was associated with -2.4 (95% CI , -4.7 to -0.2) mm Hg lower 24-hour systolic BP in Kilifi but had no effect in Nairobi/Jackson. The effect of SCT in Kilifi was limited to 30- to 59-year-old participants, among whom it was associated with -6.1 mm Hg ( CI , -10.5 to -1.8) lower 24-hour systolic BP. In pooled analysis allowing interaction by site, the effect of SCT on 24-hour systolic BP in Kilifi was -3.5 mm Hg ( CI , -6.9 to -0.1), increasing to -5.2 mm Hg ( CI , -9.5 to -0.9) when replacing estimated glomerular filtration rate with urine albumin to creatinine ratio as a covariate. In Kilifi, the prevalence ratio for hypertension was 0.86 ( CI , 0.76-0.98) for SCT and 0.89 ( CI , 0.80-0.99) for α+thalassemia. Conclusions Lifelong malaria protection is associated with lower BP in Kilifi. Confirmation of this finding at other sites and elucidating the mechanisms involved may yield new preventive and therapeutic targets.

Clinical Outcomes Associated With Sickle Cell Trait: A Systematic Review

Background

Although sickle cell trait (SCT) is largely a benign carrier state, it may increase risk for certain clinical outcomes.

Purpose

To evaluate associations between SCT and clinical outcomes in children and adults.

Data Sources

English-language searches of PubMed, CINAHL, the Cochrane Library, Current Contents Connect, Scopus, and Embase (1 January 1970 to 30 June 2018) and bibliographies of review articles.

Study Selection

Observational controlled studies (published in English) in children or adults that examined an association between SCT and any of 24 clinical outcomes specified a priori in the following 6 categories: exertion-related injury; renal, vascular, pediatric, and surgery- or trauma-related outcomes; and overall mortality.

Data Extraction

A single reviewer extracted study data, which was checked by another; 2 reviewers independently assessed study quality; and strength of evidence was assessed by consensus.

Data Synthesis

Of 7083 screened studies, 41 met inclusion criteria. High-strength evidence supported a positive association between SCT and risk for pulmonary embolism, proteinuria, and chronic kidney disease. Moderate-strength evidence supported a positive association between SCT and exertional rhabdomyolysis and a null association between SCT and deep venous thrombosis, heart failure or cardiomyopathy, stroke, and pediatric height or weight. Absolute risks for thromboembolism and rhabdomyolysis were small. For the remaining 15 clinical outcomes, data were insufficient or strength of evidence was low.

Limitation

Publication bias was possible, and high-quality evidence was scant.

Conclusion

Sickle cell trait is a risk factor for a few adverse health outcomes, such as pulmonary embolism, kidney disease, and exertional rhabdomyolysis, but does not seem to be associated with such complications as heart failure and stroke. Insufficient data or low-strength evidence exists for most speculated complications of SCT.

Primary Funding Source

National Human Genome Research Institute.