Prevalence, Awareness, Treatment, and Control of Hypertension in the United Arab Emirates: A Systematic Review and Meta-Analysis

Background: Evidence for the prevalence, awareness, treatment, and control of hypertension in the United Arab Emirates (UAE) is limited. A systematic review and meta-analysis were conducted to summarize the existing knowledge regarding the prevalence, awareness, treatment, and control of hypertension in the UAE. Methods: We searched PubMed/MEDLINE, Embase, Scopus, and Google Scholar using prespecified medical subject handling (MeSH) terms and text words to identify the relevant published articles from 1 January 1995 to 31 August 2021. Population-based prospective observational studies conducted among healthy adult subjects living in the UAE and that defined hypertension using the guidelines-recommended blood pressure (BP) cut-offs ≥ 130/80 mmHg or ≥ 140/90 mmHg were considered. Results: Of 1038 studies, fifteen cross-sectional studies were included for data extraction involving 139,907 adults with a sample size ranging from 74 to 50,138 and with cases defined as blood pressure ≥ 140/90 mmHg. The pooled prevalence of hypertension was 31% (95% confidence interval (CI): 27–36), and a higher prevalence was observed in Dubai (37%, 95% CI: 28–45) than in the Abu Dhabi region (29%, 95% CI: 24–35) and in multicenter studies (24%, 95% CI: 14–33). The level of awareness was only 29% (95% CI: 17–42), 31% (95% CI: 18–44) for treatment, and 38% (95% CI: 19–57) had controlled BP (< 140/90 mmHg). Conclusion: This study revealed a high prevalence of hypertension with low awareness and suboptimal control of hypertension. Multifaceted approaches that include the systematic measurement of BP, raising awareness, and improving hypertension diagnoses and treatments are needed.


Introduction
Hypertension, or high blood pressure (BP), is one of the most important risk factors and is a leading preventable cause of cerebrovascular, cardiovascular, and renal morbidity and mortality [1]. In 2013, the World Health Organization (WHO) set a goal to reduce hypertension prevalence by 25% by 2025, by reducing salt consumption and other public health measures [2].
Studies have found a doubling risk of ischemic heart disease and stroke with every 20 mmHg and 10 mmHg increases in systolic and diastolic BP, respectively [3]. In addition, the observational results indicated that each 10-mmHg increase in systolic blood pressure (SBP) was associated with a 45% higher risk of ischemic heart disease and stroke (65%) in those aged 55-64 years [4]. Hypertension can be diagnosed and treated early through population-based screening, and control is possible through behavioral and lifestyle changes such as decreased tobacco use, alcohol consumption, salt intake, physical activity, stress, and obesity.
Several international studies have reported global and regional variations in the prevalence, awareness, treatment, and control of hypertension [5][6][7][8]. For example, in the Middle East, findings from the Prospective Urban Rural Epidemiology (PURE) study showed that the prevalence of hypertension was high (33%) and that the lack of awareness (49%) was also high, while BP control was only 19% [8]. Although several studies investigated the burden of hypertension in the Middle Eastern countries [8][9][10][11][12], only a few reported the prevalence, awareness, treatment, and control rates. Individual studies have shown variation in the prevalence of hypertension in the UAE. For example, Hajat et al. [13] and Yousufali et al. [14] reported a prevalence rate of 23.1% and 52%, respectively.
Information on hypertension prevalence, awareness, treatment, and control is necessary to provide a baseline for monitoring, and for the development of new strategies for improving, hypertension control and resource planning. Although the early prevention of and screening for hypertension is necessary, there is evidence that suggests that there is poor disease awareness and BP control in the UAE [14][15][16]. Despite individual studies on adults in the UAE, there has been no comprehensive study on hypertension prevalence, awareness, treatment, and control. Moreover, previous systematic reviews conducted in Arabian populations did not consider studies from the UAE [17,18]. Thus, a systematic review and meta-analysis was conducted to investigate the prevalence, awareness, treatment, and control of hypertension in the UAE population.

Materials and Methods
The study protocol has been registered in the international registry of systematic reviews: PROSPERO (CRD42019141478). The systematic review and meta-analysis were both conducted following the updated Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement 2020 [19].

Search Strategy
The literature search was conducted with PubMed/MEDLINE, Scopus, Embase (Ovid ® interface), and Google Scholar to identify population-based studies published from 1 January 1995 to 31 August 2021. In addition, PROSPERO was searched for any ongoing or recently completed systematic review of the topic. A combination of Boolean operators (AND, OR, and NOT), Medical Subject Headings (MeSH), truncation (*), and text words were used to search titles and abstracts using keywords such as "hypertension", "high blood pressure", "elevated blood pressure", "prevalence", "awareness", "treatment", "control", "adults", and "United Arab Emirates." A detailed list of MeSH terms and keywords used for each database are presented in Supplemental Table S1.

Study Selection
Two researchers independently screened the titles and abstracts based on predefined inclusion criteria. All the collected articles were entered into EndNote reference Manager Software version 20 (Thomson Reuters, Stamford, CT, USA) to identify and remove duplicate records. Due to variations in reference studies from various sources, some references were manually screened. The collected articles were independently screened for their eligibility, and studies fulfilling the eligibility criteria were considered for full-text review.

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Population-based prospective observational studies, conducted among apparently healthy adult subjects living in the UAE and that defined hypertension using the guidelinesrecommended BP cut-off ≥130/80 mmHg or ≥140/90 mmHg, were considered. • Studies provided estimates of the prevalence of hypertension and investigated the level of awareness, treatment, and control of hypertension among the general population.

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Multi-country studies were included if data on the prevalence, awareness, treatment, and control of hypertension in the UAE could be distinctly extracted.

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Only peer-reviewed full-length research articles were considered.

Exclusion Criteria
• Studies conducted on diseased populations, children, and pregnant women were excluded. • Studies that did not provide the estimates in numbers or percentages were excluded. • Conference proceedings, abstracts, reviews, non-human studies, correspondences, and editorials were excluded. • Studies with unrelated outcome measures and articles with missing or insufficient data were excluded.

Operational Definitions
• Prevalence of hypertension is defined as mean SBP ≥ 140 mmHg and/or diastolic BP (DBP) ≥ 90 mmHg and/or using antihypertensive medication if hypertension was known.

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Awareness of hypertension is defined as the proportion of subjects with hypertension who reported either having been diagnosed with hypertension by a clinician or reported taking antihypertensive medications.

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Hypertension treatment was defined as the proportion of adults with hypertension who reported taking any medication for hypertension.

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Hypertension control was defined as the proportion of adults taking antihypertensive medications but who had not reached the guidelines-recommended BP targets of <130/80 mmHg or <140/90 mmHg.

Data Extraction
Following the study protocol, two researchers independently screened titles and abstracts based on the eligibility criteria. Data, such as (1) authors' names, data collection, and publication details, (2) study characteristics (study location, study design, type of settings, target population, sample size, mean age of the sample), (3) the type of device used to measure BP and the evaluation criteria, and (4) the outcome variables such as hypertension prevalence, awareness, treatment, and control, were collected.

Quality Assessment
The Newcastle-Ottawa Scale (NOS) was used to assess the methodological quality and risk of bias, and each included study was evaluated. The 7-item tool evaluated the quality of studies in three dimensions: (1) selection (4 items with one point allotted for each item: sample representativeness (1 point), sample selection procedure (1 point), exposure definition (1 point), and method of assessment (1 point)); (2) comparability (2 points); and (3) outcomes (assessment of outcomes (2 points) and statistical tests (1 point)). In accordance with the NOS scale, a maximum of nine points can be awarded to each study. An aggregated NOS score of six or more was considered high quality, whereas 0-5 indicated low quality.

Statistical Analysis
The estimates of the prevalence, awareness, treatment, and control of hypertension were expressed as proportions (%) with a corresponding 95% confidence interval (CI). The pooled prevalence estimates of each outcome variable were calculated using population size weights. The heterogeneity between the studies was assessed using the I 2 statistics (% residual variation due to heterogeneity), and Tau 2 (τ 2 ) was used for each pooled estimate. The I 2 values range between 0 and 100% and are considered as low heterogeneity for I 2 < 25%, moderate for 25-50%, and high for >50%. When the heterogeneity was high, a random-effects DerSimonian-Laird model was used in the meta-analyses. In the case of substantial heterogeneity, the source of heterogeneity was investigated using stratified analyses and a meta-regression analysis based on various study-level characteristics. The interaction between the subgroups of each factor was evaluated using the Cochran Q test, the degree of freedom (df), and the p-value results for the Cochran Q test. Funnel plots were used to assess the publication bias assessment. Egger's regression and Begg's correlation tests were used to assess the statistical significance of publication bias. The statistical analyses were performed using STATA software version 16 MP (StataCorp, College Station, TX, USA). A p-value of <0.05 was considered statistically significant.

Quality of Included Studies
The methodological quality assessment of the included studies was assessed using NOS for the cross-sectional studies. The average score of the NOS scale was 7.1 (range: 3-9). Overall, two studies were of low quality, with a NOS score of 0-5, and these studies were of a lower quality based on criteria 1 and 2 (sample selection and representativeness), criteria 5 (not report the definition of the exposure), and the appropriate statistical tests (criteria 7). Detailed results on the NOS quality assessment are presented in Supplemental Table S3.

Publication Bias
A visual examination of the funnel plots showed asymmetry and suggested that there is a source of publication bias, as shown in Supplemental Figure S1. In addition, the Egger test indicated a statistically significant publication bias for the hypertension prevalence estimates (Egger's test p = 0.017).

Discussion
Hypertension is a major and often preventable risk factor for stroke, ischemic heart disease, heart failure, other vascular diseases, and renal disease worldwide [29]. Recent data comparing the hypertension prevalence, detection, treatment, and control covering all countries worldwide from 1990 to 2019 showed a higher age-standardized prevalence of hypertension 33% (95% CI: 31-36) and identified a considerable variation in hypertension control among those who were treated [30]. In particular, the study reported that the prevalence of hypertension in the UAE is higher in men (43.9%, 95% CI: 35.4-52.9) than in women (34.5%, 95% CI: 26.9-42.4), and the control was only 18.3% (95% CI: 9.9-29.2) in men, compared to 24.6% (95% CI: 13.2-38.6) in women. However, there is no nationally representative study of the burden, treatment, and control of hypertension in the UAE. Several small studies have been conducted in different parts of the UAE and have reported on hypertension prevalence, awareness, treatment, and control. Therefore, this systematic synthesis of the available data provided comprehensive evidence of hypertension in the UAE.
To the authors' knowledge, this is the first comprehensive assessment on the prevalence, awareness, treatment, and control of hypertension in the UAE. Data from fifteen studies, comprising 139,907 participants in the UAE over the last 25 years, showed a higher prevalence of hypertension (31%), awareness (29%), treatment (31%), and control (38%). Region-specific estimates showed that hypertension is widely prevalent in Dubai (37%) and Abu Dhabi (29%). A stratified analysis showed variations in hypertension prevalence across subsets, and a higher prevalence was observed in the general public (33%) and community settings (33%) and was identified through automated BP devices (38%). Furthermore, there were considerable variations in hypertension awareness, treatment, and control across subgroups.
We carefully assessed the methodological quality of studies using accepted quality scores. There were very few low-quality studies. All the included studies used a crosssectional design and were conducted on the UAE's representative population. Region-wise variations in the prevalence of hypertension noted in this study could be due to the inclusion of a limited number of studies with a smaller sample size, the BP criteria used for diagnosis of hypertension, gender differences, study settings, and variations in the BP measurement devices. Moreover, most of the studies were conducted in cities such as Abu Dhabi and Dubai, where the hypertension prevalence and level of awareness were very high compared to other emirates. However, only one study from Ras Al Khaimah [24] with a smaller sample size (n = 74) was identified, and it reported that half of the participants were hypertensives. To overcome these discrepancies, nationwide population-representative studies are needed to understand the burden of hypertension in the UAE population.
To benchmark hypertension prevalence, awareness, treatment, and control in the UAE, pooled estimates from this study were compared to country-specific estimates of the NCD-RisC study published in Lancet 2021 [30]. Country-specific data from the Arabian Gulf countries showed that the 31% prevalence of hypertension in the UAE is lower than that in Saudi Arabia (33.3%), Bahrain (37.7%), Kuwait (39.4%), Qatar (39.7%), and Oman (43.6%) [30]. However, the UAE data presented in the Non-Communicable Disease NCD Risk Factor Collaboration (NCD-RisC) study reported that the prevalence of hypertension in the UAE was 39.2% [31], which is higher than our pooled estimates (31%). Differences in the health survey data, diagnoses and treatments of hypertension using questionnaires, BP measurement errors, validation of the BP devices, and several other residual factors may contribute to the differences in estimating the prevalence of hypertension.
Comparing the level of hypertension awareness, treatment, and control to data from other high-income countries [5] showed that the level of awareness in the UAE (29%) was much lower than in Australia (74%), Canada (83%), Germany (87%), Japan (70%), New Zealand (74%), South Korea (79%), the United Kingdom (72%), and the United States of America (USA) (84%). Similarly, the hypertension control in the UAE (38%) that was observed in this study was lower than in Canada (66%), Germany (53%), South Korea (50%), and the USA (50%), but higher than in Australia (33%), New Zealand (31%) and Japan (25%) [5]. Variations in the combination of the enabling factors of high prevalence, low awareness, and poor hypertension control calls for an urgent response in line with Sustainable Development Goals (SDG) target 3.4 on Non-communicable Diseases (NCDs) to lower hypertension prevalence or control BP through both improved prevention and improving early-stage treatment cascades [2,31]. The changing prevalence of hypertension in the UAE is mainly due to changing lifestyles with lower physical activity and a shift from a traditional diet that is high in fiber to energy-dense processed food high in fat, sugar, and salt [32][33][34]. Furthermore, studies consistently reported a significantly increased burden of overweight and obesity [35], metabolic syndrome [36], and cardiovascular risk factors [37] among the younger population in recent decades. Therefore, public health authorities should initiate multifaceted interventions to control the pervasive burden of hypertension in the UAE.

Strengths and Limitations
There are several strengths and some limitations in this study. This systematic review and meta-analyses consolidated the quantitative evidence on the prevalence, awareness, treatment, and control of hypertension in the UAE from 1995 to 2021. We employed a comprehensive search strategy across several data sources, involved many study participants in providing pooled estimates, and thoroughly assessed the risk of bias in each of the 15 observational studies. Furthermore, we conducted stratified meta-analyses to investigate the potential source of heterogeneity between the studies and subgroups.
Similar to all systematic reviews and meta-analyses, our study has some limitations. First, baseline characteristics, such as geographic area, differences in the culture, BP assessment methods, health settings, population characteristics, and practices, vary widely across the UAE, which might influence our results. Second, the outcomes reported in this study were obtained from cross-sectional studies, and thus are not conclusive to generalize to the UAE population. Third, high heterogeneity was observed across all of the outcomes; this might be due to several underlying reasons that warrant further investigation; we performed a stratified analysis and a subgroup analysis to investigate the source of heterogeneity. Fourth, low power and precision may have contributed to higher heterogeneity (Cochran Q) and I 2 . Fifth, the Egger test suggested a publication bias in the pooled prevalence of hypertension in the UAE. Thus, caution is needed when interpreting the findings.

Conclusions
Our findings indicated that a significant prevalence of hypertension, poor awareness, and suboptimal BP control was observed in the UAE-nearly one in three adults have hypertension while one in five control it. Significant regional differences exist in hypertension prevalence and care in the UAE. These findings highlight the urgent need for multifaceted interventions that include the early screening for and detection of BP-particularly in high-risk populations-raising awareness, and improving hypertension diagnoses and treatments.