Cardiovascular disease is the leading global cause of death and disability, causing about 17 million deaths per year, about a third of all deaths worldwide. Of these, 9.4 million deaths are due to hypertension-related complications.1 Hypertension is an important risk factor for developing cardiovascular disease, and is estimated to be responsible for at least 45% of all deaths due to heart disease and 51% of deaths due to stroke.2

Epidemiological studies suggest that there is a continuous increase in the risk of developing cardiovascular disease, stroke and kidney disease with increasing systolic (SBP) and diastolic (DBP) blood pressure levels.3,4 In 2008, approximately 40% of adults aged over 25 years worldwide had been diagnosed with hypertension.5 In Europe, the European Health Examination Survey (EHES) Pilot Project reported a hypertension prevalence of 33.1% among men and 22.8% among women (aged 25-64 years), although with considerable variation in blood pressure measurements between different populations.6

In Portugal, high hypertension prevalences have been previously reported for the general population.7,8 Two studies, representative of the Portuguese population (aged 18-90 years, Portuguese mainland), which included blood pressure measurement, have been performed: one in 2003 (the PAP study), which reported a prevalence of 42.1%,9 and the other in 2011-2012 (the PHYSA study),10 in which the prevalence was 42.2%. In 2014, the fifth Portuguese National Health Survey estimated a lower prevalence of hypertension (24.5%), but this was based on the Portuguese population over 15 years old and on self-reported data.11

Monitoring hypertension prevalence in the Portuguese population is essential for public health planning, especially for the definition of health strategies in primary prevention, such as nutrition policies, and also hypertension management, resource allocation and appraisal of health programs. Moreover, indicators of availability of and compliance with appropriate treatment (prevalence of individuals who are aware of their condition, are being treated and have hypertension under control) also need to be nationally monitored, which will help public health professionals to tailor strategies of hypertension prevention for high-risk individuals.

Given this context, the aim of this study was firstly to estimate and describe the distribution of hypertension prevalence in the Portuguese population in 2015, and secondly to estimate the distribution of awareness, treatment and control of hypertension.

The 2015 Portuguese National Health Examination Survey (INSEF) was a cross-sectional population-based study by the National Health Institute Doutor Ricardo Jorge (INSA) in cooperation with the five Regional Health Administrations, the two Regional Health Secretariats of the Autonomous Regions of the Azores and Madeira, and the Norwegian Institute of Public Health.12

The INSEF study was approved by the Ethics Committee of the Portuguese National Health Institute Doutor Ricardo Jorge, the National Data Protection Commission (CNPD), and eight regional ethics committees. Written informed consent was obtained from all participants before data collection.

Of the 12289 selected individuals, 4911 participated in INSEF 2015, leading to a participation rate of 43.9%. Only one individual did not undergo blood pressure measurement due to a medical condition.

The participants’ characteristics are described in Supplementary Table 1. Participants were mostly married or in a civil union (68.4%), of working age (84.3% aged 25-64 years); 27.7% had only the first cycle or no education, 73.6% lived in an urban area and 61.9% were employed.

Mean SBP and DBP were 125.4 mmHg (95% confidence interval [CI]: 124.3-126.3; standard deviation [SD]: 16.0) and 73.9 mmHg (95% CI: 73.2-74.7; SD: 10.0), respectively. Both SBP and DBP were higher in males (SBP: 130.0 mmHg, 95% CI: 128.8-131.3, SD: 14.5 and DBP: 76.0 mmHg, 95% CI: 75.1-76.8, SD: 9.9) than in females (SBP: 121.0 mmHg, 95% CI: 119.5-122.6, SD: 16.1 and DBP: 72.1 mmHg, 95% CI: 71.1-73.2, SD: 9.7).

The overall hypertension prevalence was 36.0% (95% CI: 34.3-37.7). A significantly higher prevalence was observed in males (39.6%, 95% CI: 36.5-42.8) than in females (32.7%, 95% CI: 30.1-35.5). Prevalence increased with age, reaching 71.3% in the 65-74 age group. The highest prevalences were found among individuals with the first cycle or no formal education, those who had no formal occupation (student, retired or homemaker) and those who reported being married or in a civil union (Table 1).

An association was found between hypertension, male gender and being married or in a civil union, while an increase in prevalence was found with age, lower educational level and having an occupational status other than employed or unemployed.

After adjustment, the association with age, education and occupation decreased and no statistical association was found with marital status (Table 2). Nevertheless, the highest aPR was observed among individuals aged between 65 and 74 years, who had no or only the first cycle of basic education, males, and those who had an occupational status other than employed or unemployed (Table 2). In this subgroup (n=214), the hypertension prevalence was 80.9% (95% CI: 74.5-85.9).

Given that no effect modification was found related to gender, adjusted prevalence ratios were not stratified by gender.

Among hypertensive individuals, 69.8% were aware of their condition and 69.4% were under medical treatment. The proportions of individuals who were aware of their condition and who were under medical treatment were higher among females (77.8% and 78.9%, respectively) than males (62.5% and 60.7%) and increased with age in both sexes (Table 3).

Of those under medical treatment, 71.3% had optimal blood pressure levels, and no significant differences were found in gender or age group (Table 3).

At the population level 25.0% (95% CI: 23.3-26.7) of individuals aged 25-74 years were taking antihypertensive medication.

Overall, 82.2% of the population aged 25-74 years reported having had their blood pressure measured by a health professional in the 12 months prior to the interview and almost half (46.1%) reported having had it measured in the previous three months. The proportion of individuals whose blood pressure had been measured in the three months before the interview increased with age (60.4% in the oldest age group) and was higher among females (49.7%).

Only 0.7% of all participants reported never having had their blood pressure measured. Although the point estimate was higher among male participants (1.1%), no significant differences were found between the sexes (Table 4).

Hypertension is a major risk factor for cardiovascular disease in the Portuguese population, and its prevalence increases with age, reaching more than 70% of the population aged 65-74 years in 2015. In our overall study population, 36.0% of those aged between 25 and 74 years had hypertension. Higher prevalences were observed in males, older individuals (65-74 years), those who had no or only the first cycle of basic education, and those with occupational status other than employed or unemployed. Regarding those classified as having hypertension, 69.8% were aware of their condition, 69.4% were under medical treatment and 71.3% of treated individuals reached optimal blood pressure levels.

There is evidence that those who do not participate in health surveys are less interested in their own health, have less healthy behaviors and are less healthy than those who agree to participate.20–23 As our participation rate was 43.9%, potential differences between participants and non-participants could have biased our results, most likely toward underestimation of the prevalence of hypertension. However, self-reported use of antihypertensive drugs was similar between participants (25.0%) and non-participants (26.0%) (Supplementary Table 2), suggesting that this selection bias had at most a minor effect on our estimates. The fact that we followed the procedures recommended for the EHES,13,14 performing a prior pilot study, training staff in study procedures, using comparable target populations and monitoring data quality during the survey, may have helped to minimize misclassification bias.

Compared to previous studies performed in representative samples of the Portuguese population that used direct blood pressure measurements, a slightly lower hypertension prevalence was found (42.1% in the PAP study in 20039 and 42.2% in the PHYSA study, 2011-1210). Nevertheless, when comparing hypertension prevalence by age group and gender between the three studies, significant differences were only observed with the PAP study.9,10 It cannot therefore be excluded that the observed differences may derive to some extent from studying a younger population than that used in previous studies.

The higher prevalence observed in males6,9,10 and in older individuals6,8–10 was in line with previous studies and showed hypertension to be a major cardiovascular risk factor in the adult Portuguese population. Although biological factors also potentially play a part, the differences found highlight disparities in the distribution of risk factors for hypertension between the sexes and between socioeconomic groups. For instance, a higher prevalence of smoking24 and higher salt consumption10 have been observed in Portuguese males.

Regarding self-awareness of hypertension, there was a higher proportion of individuals aware of their condition in 2015 than in 2003 (69.8% vs. 45.7%). However, compared to figures for 2011-12, awareness was lower in 2015 (69.8% vs. 76.6%). The same was found regarding the proportion of individuals under medical treatment (INSEF, 2015: 69.4%; PAP, 2003: 38.9% and PHYSA, 2011-12: 74.9%). It is important to highlight the increase in the number of treated individuals who reached optimal blood pressure levels over the years in all age groups compared to previous studies (PAP, 2003: 11.2%; PHYSA, 2011-12: 42.5%; INSEF, 2015: 71.3%).9,10 However, the target populations in 2003 and 2011-12 (age 18-90 years, mainland population only) were not fully comparable to the target population studied in 2015 (age 25-74 years, including Madeira and the Azores), which may explain the differences observed. Moreover, the observed differences may still be due to different procedures being used for blood pressure measurement in each study.

Although 82.2% of the adult Portuguese population (age 25-74 years) reported having had their blood pressure measured in the 12 months preceding the interview, only 69.8% of hypertensive individuals were aware of their condition. This may be explained by the high hypertension incidence observed in Portugal,25 but may also indicate a low level of understanding of their condition, particularly if no pharmacological treatment was prescribed.

Males had their blood pressure measured less frequently and were less likely to be aware of their condition and consequently to be under medical treatment. Considering that the highest hypertension prevalence was observed in males, this may indicate a misunderstanding of the risk of having high blood pressure.

In addition, the lowest level of hypertension awareness was found in those aged 25-44 years, which suggests that they had a low perception of their risk. Although this age group has a lower incidence of hypertension than the other age groups, studies show that hypertension is no longer an uncommon condition at younger ages, which is in agreement with the increasing hypertension incidence observed in young Portuguese adults in recent years.25

Our results appear to be in line with the decrease in mortality from cardiovascular and cerebrovascular disease observed in Portugal in the last decade,26 although this remains above the average for European Union countries. These findings coincide with preventive measures implemented by the National Programs for Cerebro- and Cardiovascular Diseases, Prevention and Control of Tobacco Use, and Promotion of Healthy Nutrition. These measures include approval and implementation of a national law reducing levels of salt in bread, and entering into contracts with primary healthcare units to achieve specific levels of control in hypertensive patients. Although the value of some of these preventive actions is well known,27 it would be useful to estimate their effect in Portugal, particularly of those related to delivery of care and organization of local services. Using national surveys to monitor hypertension indicators (mortality, incidence, prevalence and control) will help to assess different preventive measures implemented over time.

This study indicates that a large majority of the adult Portuguese population are likely to reach blood pressure levels defined as hypertension during adulthood. Differences in hypertension prevalence by age, gender and socioeconomic status highlight the need to implement wide-population strategies that do not increase heath inequalities. Primordial and primary prevention strategies targeting hypertension risk factors such as smoking, alcohol consumption, salt intake and lack of exercise throughout life may reduce hypertension incidence in the future while avoiding health inequalities. In addition, secondary and tertiary prevention strategies are still needed, given the high prevalence observed, and should be directed at the most affected population groups (males, those aged 65-74 years and those with little or no formal education).

The Portuguese National Health Examination Survey was developed as part of the project “Improvement of epidemiological health information to support public health decision and management in Portugal. Towards reduced inequalities, improved health, and bilateral cooperation”, which received a €1,500,000 grant from Iceland, Liechtenstein and Norway through the EEA and Norway Grants.

The authors have no conflicts of interest to declare.