Hypertension is the most important risk factor for cardiovascular and cerebrovascular disease, particularly myocardial infarction and stroke, which are major causes of morbidity and mortality throughout the world.1–3 In 2008, the global prevalence of hypertension in adults aged ≥25 years was 40%, despite falling between 1980 and 2008.4,5

For the last 30 years, Portugal has been among the countries with the highest levels of mean blood pressure (BP).6,7 In 2008, the prevalence of hypertension (or use of antihypertensive medication) in adults aged ≥25 years was estimated at 41.9% (46.5% in men and 37.4% in women).8 Between 1980 and 2008 mean systolic BP fell, particularly in women.8

Knowledge of the evolution, trends and current status of epidemiological measures of hypertension (incidence, prevalence and associated mortality) is important for planning, implementation and evaluation of public health measures.9

A recent systematic review by Pereira et al. concluded that between 1990 and 2005, the prevalence of hypertension (defined as systolic and/or diastolic BP ≥140/90 mmHg) remained approximately constant in young adults and decreased in middle-aged and older adults, whereas the prevalence of self-reported hypertension increased by 0.4% per year in the same period.10

Systematic reviews have generally been the preferred method of literature review, but the growing volume and importance of health research has led to the development of alternative forms of structured review, including scoping reviews, which are increasingly used in public health research.11 Although these may appear simpler than a systematic review, scoping reviews retain a similar organization and transparency. They have been described as a technique to ‘map’ relevant literature on a particular subject in order to obtain an overall picture of current knowledge,11,12 and are mainly used to identify gaps in knowledge and/or to summarize the most important studies in a specific field.13 The main difference from systematic reviews is that the latter aim to provide an initial evaluation of the quality of studies and a quantitative and qualitative summary of results, while scoping reviews do not set out to evaluate the quality of studies, but to give a qualitative review of the scope, methods and results of existing research.14

So far as we know, no studies aimed at describing the scope and results in a particular area of health care research have been published in Portugal using the scoping review methodology. Such a review is of particular importance in relation to hypertension, given the prevalence of the disease and the need to identify any gaps in knowledge in order to define research priorities.

The aim of this study is to perform a scoping review on the prevalence and incidence of hypertension in the Portuguese population describing the scope (quantity, focus and nature)14,15 of research and to summarize the main results.

The review was conducted during June 2013 by two investigators working simultaneously. A panel of three experts (researchers with experience in health care, clinical practice, public health, epidemiology and health research) validated the methodology used (search terms, inclusion and exclusion criteria, information sources, and summary and analysis of the results).12 The framework of the study was divided into the following stages (Figure 1), in accordance with the methodology proposed by Arksey and O’Malley14: (1) identifying the research question; (2) identifying relevant studies; (3) selection of studies based on pre-established inclusion criteria; (4) data collection; and (5) summarizing and reporting the results.

Figure 1.

Methodology of the scoping review.

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We included studies on the prevalence of hypertension based on data collected after 2005, those published after 2005 with an unspecified date of data collection, and those published after 2011 even if data collection was before 2005. The review thus covered publications not included in the 2012 review by Pereira et al.10 of trends in hypertension prevalence in Portugal in 1990–2005, in order to update and widen the scope of knowledge, although some studies may appear in both reviews.

Studies on the incidence of hypertension published between January 1995 and June 2013 were included, in order to cover the largest number of publications.

The information sources used were the Portuguese Biblioteca do Conhecimento Online (B-on – Online Knowledge Library), run by the Fundação para a Computação Científica Nacional (Foundation for National Scientific Computation),16 and PubMed, maintained by the US National Library of Medicine.17

We searched for studies in Portuguese and English only (Figure 1), combining the search terms with the Boolean operator AND. In B-on, the Portuguese search terms used were ‘prevalência’ AND ‘hipertensão’, and ‘incidência’ AND ‘hipertensão’. In PubMed the terms used were ‘prevalence’ AND ‘hypertension’ AND ‘Portugal’, and ‘incidence’ AND ‘hypertension’ AND ‘Portugal’.

PubMed is known to be a good source of information for studies on chronic diseases.18 We also searched B-on using Portuguese search terms only in order to include studies in Portuguese journals, since PubMed does not index all journals published in Portugal.

Studies on hypertension in populations with specific characteristics, such as diabetic or obese individuals, were excluded. No inclusion criteria were established in terms of study design, type of publication, or age of the study population, and, as recommended for scoping reviews,14 the quality of the study was not used as an inclusion criterion.

Data on the following variables were collected and entered into a standard table: author(s), publication year, study location, sample size, BP measurement methods, main results, and stratification by gender and age. The information was entered into the table as the studies were selected and the data were subsequently analyzed in terms of quantity (number of studies), focus (populations, age-groups, diagnosed vs. self-reported hypertension, etc.), and nature (type of research).14,15

The population that has been the subject of the largest number of studies on hypertension prevalence was that of the North region, particularly the city of Porto. No study has dealt exclusively with the Alentejo and Algarve regions, a gap in knowledge that should be filled by new studies or publication of existing data. However, the national studies by Cortez-Dias et al.25 and Perdigão et al.21 include estimates of measured and self-reported hypertension, respectively, for these regions: 51.54% and 44.57% (measured) and 23% and 18.3% (self-reported) for the Alentejo and the Algarve, respectively.

We found long delays between data collection and publication of results (up to nine years).26 This implies that studies on recent data may not yet have been published. For instance, the Portuguese HYpertension and SAlt Study (PHYSA), conducted by the Portuguese Society of Hypertension, collected data on a representative sample of 3720 residents of mainland Portugal in 2012 but had not published its results when this review was completed.27

The studies on hypertension prevalence in children and/or adolescents used similar definitions of hypertension and BP measurement methods (at or above the 95th percentile and digital devices), in accordance with the US guidelines on high blood pressure in children and adolescents, which are used internationally.28 This facilitates comparisons between the results of different studies and monitoring of developments in hypertension prevalence in these population groups. However, there were methodological differences between the studies: three made three BP measurements and two made only one, while two studies took measurements in both arms, two in the right arm, and one did not specify. According to the US guidelines BP should be measured in the right arm.28

Of the nine studies on hypertension prevalence in adults, hypertension was self-reported in only two and BP was measured in the others. Hypertension was defined as BP ≥140/90 mmHg. Only five studies reported the type of measurement device used (which varied widely), and only one study specified which arm was used. These findings indicate inadequate description of methods, which hinders comparisons between studies. According to a recent review by Crim et al.,29 surveillance definitions of hypertension vary in the literature, and clear definitions of measurement methods are crucial for monitoring its prevalence and incidence. Crim et al. propose standard definitions to be used in research in this area.

According to the guideline of the Portuguese Directorate-General of Health (DGS) entitled “Hipertensão arterial: Definição e classificação” (“Hypertension: definition and classification”), a diagnosis of hypertension should be based on at least two measurements, in the arm that gives the higher BP reading.30,31 This was not followed in any of the studies in this scoping review; the studies by Cortez-Dias et al.25 and Brandão et al.32 describe the measurement method used except for the arm used, and state that they followed the American Heart Association guidelines,33 which are similar to the recommendations of the DGS.

Only two of the studies on hypertension prevalence present results stratified by both age and gender, which is a significant obstacle to an understanding of the epidemiology of the disease.29

In all the studies on adults with results stratified by gender in which BP was measured, hypertension prevalence was lower in women, in agreement with the systematic review by Pereira et al.10 and the World Health Organization figures for Portugal in 2008.4

In the only study which presented self-reported hypertension prevalence and results stratified by gender, the prevalence was lower in men, as also reported by Pereira et al.10

The fact that the studies on adults selected for this review use different BP measurement methods, not specified in many cases, and are infrequently stratified by age and gender, seriously hinders comparisons and analysis. This will of course have an effect on knowledge of the epidemiology of hypertension in Portugal and hence on implementation of health care policies and measures.

The results of our study reveal the need for greater uniformity in measurement and reporting methods for research into hypertension, in order to improve the comparability, data collection and analysis of studies on the evolution and trends in hypertension in the Portuguese population. They also point up the need to perform a quantitative analysis of the variability of data resulting from the application of different BP measurement methods.

Regarding hypertension incidence, the two selected studies were of very different populations: residents of the city of Porto, and the general Portuguese population. In the Porto study (1999–2003), incidence was 57.3/1000 population/year, while in the 2011 national report from the general practitioner sentinel network it was 6.54/1000 population/year. This discrepancy may reflect a fall in incidence between 2003 and 2011, or it may be due simply to differences in sample size, target populations and measurement methods.

The existence of only two studies since 1995 on hypertension incidence in Portugal reveals a gap in knowledge in this area that should prompt future research.

The present scoping review of research into the prevalence and incidence of hypertension in the Portuguese population allows the following conclusions to be drawn: (i) in the last eight years, more studies have been published on populations in the North region; (ii) although the Alentejo and Algarve regions were included in two national studies, their populations have not been specifically targeted in any published studies; (iii) there have been long delays between data collection and publication of results on hypertension prevalence (up to nine years), which hinders comparison of these studies with others in which data collection was nearer to publication date; (iv) only two studies on hypertension incidence were published between 1995 and 2013, which reveals a gap in knowledge that needs to be filled; and (v) differences in blood pressure measurement methods, not specified in most studies, and the infrequency of stratification of results by gender and age, hinder comparison and analysis, and hence monitoring of trends in the incidence and prevalence of hypertension in Portugal.

The authors have no conflicts of interest to declare.