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. 2023 Oct 19;65:102275. doi: 10.1016/j.eclinm.2023.102275

Sociodemographic and health-related differences in undiagnosed hypertension in the health survey for England 2015–2019: a cross-sectional cohort study

Emma Campbell a, Ellie Macey a, Chris Shine a, Vahé Nafilyan a, Nathan Cadogan Clark a, Piotr Pawelek a, Isobel Ward a, Andrew Hughes b, Veena Raleigh c, Amitava Banerjee d, Katie Finning a,
PMCID: PMC10725049  PMID: 38106553

Summary

Background

Hypertension is a leading cause of morbidity and mortality worldwide, yet a substantial proportion of cases are undiagnosed. Understanding the scale of undiagnosed hypertension and identifying groups most at risk is important to inform approaches to detection.

Methods

In this cross-sectional cohort study, we used data from the 2015 to 2019 Health Survey for England, an annual, cross-sectional, nationally representative survey. The survey follows a multi-stage stratified probability sampling design, involving a random sample of primary sampling units based on postcode sectors, followed by a random sample of postal addresses within these units. Within each selected household, all adults (aged ≥16 years) and up to four children, were eligible for participation. For the current study, individuals aged 16 years and over who were not pregnant and had valid blood pressure data were included in the analysis. The primary outcome was undiagnosed hypertension, defined by a measured blood pressure of 140/90 mmHg or above but no history of diagnosis. Age-adjusted prevalence of undiagnosed hypertension was estimated across sociodemographic and health-related characteristics, including ethnicity, region, rural-urban classification, relationship status, highest educational qualification, National Statistics Socio-Economic Classification (NS-SEC), Body Mass Index (BMI), self-reported general health, and smoking status. To assess the independent association between undiagnosed hypertension and each characteristic, we fitted a logistic regression model adjusted for sociodemographic factors.

Findings

The sample included 21,476 individuals, of whom 55.8% were female and 89.3% reported a White ethnic background. An estimated 30.7% (95% confidence interval 29.0–32.4) of men with hypertension and 27.6% (26.1–29.1) of women with hypertension were undiagnosed. Younger age, lower BMI, and better self-reported general health were associated with an increased likelihood of hypertension being undiagnosed for men and women. Living in rural areas and in regions outside of London and the East of England were also associated with an increased likelihood of hypertension being undiagnosed for men, as were being married or in a civil partnership and having higher educational qualifications for women.

Interpretation

Hypertension is commonly undiagnosed, and some of the groups that are at the lowest risk of hypertension are the most likely to be undiagnosed. Given the high lifetime risk of hypertension and its strong links with morbidity and mortality, our findings suggest a need for greater awareness of the potential for undiagnosed hypertension, including among those typically considered ‘low risk’. Further research is needed to assess the impact of extending hypertension screening to lower-risk groups.

Funding

None.

Keywords: Hypertension, High blood pressure, Undiagnosed hypertension, Health inequalities


Research in context.

Evidence before this study

We searched PubMed from database inception to June 26, 2023 using the search terms (“high blood pressure” OR “hypertension”) AND “undiagnosed”, with no language restrictions. Several studies reported undiagnosed hypertension prevalence estimates for countries including England, the United States, India, Rwanda, Croatia, and France. These studies used a variety of methods to assess undiagnosed hypertension, and some were focused on specific groups such as hospital in-patients, immigrants, older adults, or people with overweight/obesity. Only a handful of studies reported the prevalence of undiagnosed hypertension by characteristics using a general population sample. For example, a 2023 study in Croatia found that men and younger adults were more likely to be undiagnosed than women and older adults, and a 2019 study in France found that men, individuals with no cardiovascular disease or diabetes, and those with a lower waist circumference had the highest odds of undiagnosed hypertension. There was very little evidence for undiagnosed hypertension by characteristics among adults in England, with one study, published in 2020, investigating differences in undiagnosed hypertension in England by income. That study found that men in high-income households were more likely to be undiagnosed than men in low-income households but found no difference by income for women.

Added value of this study

To our knowledge, there has been no previous research to examine undiagnosed hypertension by a wide range of sociodemographic and health-related characteristics among adults in England. We estimated the prevalence of hypertension and undiagnosed hypertension by sex and age, followed by age-adjusted estimates by ethnicity, region, rural-urban classification, relationship status, highest educational qualification, National Statistics Socio-Economic Classification (NS-SEC), Body Mass Index (BMI), self-reported general health, and smoking status. We fitted logistic regression models to assess the independent association of each characteristic with undiagnosed hypertension after adjusting for sociodemographic factors. This study adds to the existing evidence on the prevalence of undiagnosed hypertension in England and provides novel insights into which groups of the population are most at risk of being undiagnosed.

Implications of all the available evidence

A substantial proportion of hypertension cases in England are undiagnosed. Some of the groups who are less likely to have hypertension, such as younger adults and those with a lower BMI, are more likely to be undiagnosed if they do have hypertension. Given the high lifetime risk of hypertension, its strong associations with morbidity and mortality, and the health and economic benefits of early identification and intervention, the available evidence suggests a need for awareness among healthcare professionals and the public of the potential for undiagnosed hypertension across all population groups, including those typically considered low risk. There may be substantial benefit in ensuring accessibility of blood pressure assessment for all groups, including young adults and individuals who are not routinely in contact with healthcare services. However, further evidence is needed to understand the effectiveness of community-based or self-screening methods for reducing hypertension-related morbidity and mortality.

Introduction

Hypertension is a leading cause of morbidity and mortality worldwide and is responsible for between 8 and 10 million deaths each year,1, 2, 3 while high blood pressure accounted for an estimated 9% of global Disability-Adjusted Life Years in 2019.4 In England, 28% of adults had hypertension in 2019, defined as having a measured blood pressure of 140/90 mmHg or above or self-reporting antihypertensive medication use.5 Hypertension also places considerable burden on health services and is responsible for 12% of all visits to General Practitioners in England, with an estimated annual cost to the National Health Service of over £2 billion.6

Lowering blood pressure is a well-established strategy for reducing the incidence of cardiovascular diseases such as stroke, myocardial infarction, and coronary heart disease, and is associated with a significant reduction in all-cause mortality.7,8 Early identification and treatment are associated with significant health and economic benefits because they reduce the need for more elaborate and costly interventions required to treat the complications of hypertension.2,3 Hypertension prevention focuses on lifestyle interventions such as eating a healthy diet, taking regular exercise, and reducing alcohol consumption, and the National Institute for Health and Care Excellence (NICE) in England recommends the same lifestyle interventions for individuals diagnosed with hypertension.9 This is followed by antihypertensive medication if blood pressure is not successfully controlled through lifestyle interventions alone.

Hypertension rarely causes symptoms in the early stages and a substantial proportion of cases are undiagnosed.2,3 A review of hypertension trends between 1990 and 2019 found that 41% of women and 51% of men with hypertension globally did not report a diagnosis,2 and previous estimates suggest that around one third of hypertension cases in England are undiagnosed.10 In 2019, a new coalition led by Public Health England and NHS England outlined plans to improve detection and prevention of the major causes of cardiovascular disease, including an ambition to diagnose 80% of hypertension cases by 2029.11 However, there was a substantial decrease in the proportion of hypertension cases diagnosed and treated during the COVID-19 pandemic, leading to a backlog of care and an urgent need to identify those who are undiagnosed.12,13

Previous research has identified groups who are at increased risk of hypertension. This includes older adults, males, individuals belonging to Black ethnic groups, and those living in more deprived areas, as well as those with known health-related risk factors such as being overweight or physically inactive.3,5,14,15 However, less is known about which groups are most likely to be undiagnosed. Limited evidence from international research has suggested that among those with hypertension, younger adults, men, and those without common comorbidities like diabetes or cardiovascular disease are more likely to be undiagnosed than older adults, women, and those with comorbidities.16,17 One previous study in England found that men in high-income households were more likely to have undiagnosed hypertension than men in low-income households, but no differences were found by income for women.10 However, there have been no studies to explore undiagnosed hypertension by a wide-range of sociodemographic and health-related characteristics among adults in England. Better understanding of inequalities in undiagnosed hypertension could lead to improved rates of diagnosis through targeted screening or public health campaigns. This study aims to identify sociodemographic and health- and lifestyle-related differences in undiagnosed hypertension using a nationally representative sample of adults in England.

Methods

Study population

We used data from the Health Survey for England (HSE), an annual cross-sectional survey of people living in private households in England.5 We pooled data from the 2015 to 2019 surveys, which were the most recent data years available at the time of analysis. Aggregating five years of survey data was considered to achieve a good balance between achieving an adequate sample size for analysis while minimising the risk of changes in associations that may occur over time. The HSE follows a multi-stage stratified probability sampling design, involving a random sample of primary sampling units (PSUs) based on postcode sectors, followed by a random sample of postal addresses within PSUs. Within each selected household, all adults aged 16 years and over, and up to four children, were eligible for participation. Full details of the sampling methods are available via NHS Digital.5 All adult participants complete a health interview, which includes questions on demographic characteristics and health history. Participants are then visited by a study nurse who takes measurements such as blood pressure. Prior to 2018 all adult participants were eligible for a nurse visit and in 2018–2019 89% of surveyed addresses were randomly selected for a nurse visit. However, some eligible participants did not complete the nurse visit. The proportion of adult participants who completed a nurse visit between 2015 and 2019 ranged from 59% to 67%. Our analytical sample was restricted to respondents from the 2015 to 2019 HSE who were aged 16 years and over, were not pregnant at the time of interview, and had valid blood pressure data. Fig. 1 shows the flow of survey respondents.

Fig. 1.

Fig. 1

Flow chart of sample selection.

Outcomes

Self-reported diagnosis of hypertension

Participants were asked “Do you now have, or have you ever had high blood pressure (sometimes called hypertension)?”. If answered yes, participants were asked “Were you told by a doctor or nurse that you had high blood pressure?”. We classified participants as having self-reported diagnosed hypertension if they answered ‘yes’ to both questions and the high blood pressure didn't occur only during pregnancy.

Blood pressure measurement

During the nurse visit, three consecutive blood pressure readings were taken. We used the mean of the second and third measurements, in line with previous research and guidelines.10,18 We classified participants as having high blood pressure if their systolic pressure was 140 mmHg or above or their diastolic pressure was 90 mmHg or above.

Total hypertension and undiagnosed hypertension

We used the variables above to derive our two outcomes of interest: (1) total hypertension - individuals who self-reported a diagnosis of hypertension or had a blood pressure measurement of 140/90 mmHg or above; and (2) undiagnosed hypertension – individuals whose blood pressure measurement was 140/90 mmHg or above but who did not self-report a diagnosis of hypertension.

Predictors

We explored a variety of sociodemographic and health-related predictors of hypertension and undiagnosed hypertension, based on the literature, theoretical relevance, and data availability. These were: sex, age group, ethnicity, region, rural-urban classification, relationship status, highest educational qualification, National Statistics Socio-Economic Classification (NS-SEC), Body Mass Index (BMI), self-reported general health, and smoking status. These were all collected during the health interview. Details of data collection methods and variable levels for all predictors are available in Supplementary Material Table S1.

Statistical analysis

All analyses accounted for the complex survey design and incorporated weights that were pre-calculated by the HSE survey team. These accounted for selection, non-response, and population profile in the main sample, as well as non-response bias introduced through the nurse visits. Full details of the methodology for deriving each of these weights are provided in the HSE methods report.5 Weights were re-scaled to the pooled dataset and sub-sample of interest (adults who were not pregnant and had valid blood pressure data), following guidance provided by the HSE survey team. This involved calculating the mean value of the weight for each year within the subsample and dividing the combined weights by their respective means.

For each predictor we estimated the age-adjusted prevalence of (a) total hypertension among all adults and (b) undiagnosed hypertension among those with hypertension, by fitting logistic regression models adjusted for age (in five-year age bands, the most granular level available). Marginal means were then used to estimate the age-adjusted prevalence with hypertension and undiagnosed hypertension in each group. Second, we examined the odds of hypertension being undiagnosed for each of our predictors after adjusting for other factors. We fitted minimally adjusted logistic regression models (adjusted for age and stratified by sex) followed by fully adjusted models that adjusted for age, ethnicity, region, urban-rural classification, relationship status, highest educational qualification, and NS-SEC. These covariates were selected based on previous research and topic knowledge and excluded any variables we considered likely to be on the causal pathway between the predictors and the outcome. Statistically significant interactions were identified between sex and several of our predictor variables, therefore all analyses were stratified by sex. All analyses were performed on a complete case basis as there were negligible missing data (<0.2%) for all variables except BMI (10% missing). As BMI was not a covariate in adjusted models this only impacted analysis where BMI was the predictor. Tests of statistical significance were not performed as the analysis was primarily descriptive in nature. All analyses were specified a-priori in the study protocol (see Supplementary Material). Analyses were conducted using R version 4.0.2.

Ethics

Ethical approval for this analysis was granted by the UK Statistics Authority Data Ethics Team, falling under the National Statistician's Data Ethics Advisory Committee. All survey respondents provided verbal informed consent to participate in the Health Survey for England.

Role of the funding source

There was no dedicated external funding for this research.

Results

Characteristics of the sample

The sample involved 21,476 individuals; 55.8% were female, 89.3% reported a White ethnic background, and all were recruited to the Health Survey for England between January 2015 and March 2020. Table 1 summarises the characteristics of the sample.

Table 1.

Characteristics of the sample.

Sample N (%)
Sex
 Male 9485 (44.2)
 Female 11,991 (55.8)
Age group
 16–24 years 1438 (6.7)
 25–34 years 2599 (12.1)
 35–44 years 3268 (15.2)
 45–54 years 3643 (17.0)
 55–64 years 3776 (17.6)
 65–74 years 3894 (18.1)
 75 years and over 2858 (13.3)
Ethnicity
 White 19,156 (89.3)
 Black 527 (2.5)
 Asian 1340 (6.2)
 Other 438 (2.0)
Region
 East Midlands 2015 (9.4)
 East of England 2586 (12.0)
 London 2262 (10.5)
 North East 1881 (8.8)
 North West 2826 (13.2)
 South East 3618 (16.8)
 South West 2281 (10.6)
 West Midlands 2055 (9.6)
 Yorkshire and the Humber 1952 (9.1)
Rural-urban classification
 Urban 16,884 (78.6)
 Rural 4588 (21.4)
Relationship status
 Single 3422 (15.9)
 Married or civil partnership 11,900 (55.4)
 Cohabiting 2446 (11.4)
 Separated or divorced 2060 (9.6)
 Widowed or surviving partner 1645 (7.7)
Educational qualifications
 Degree or equivalent qualification 6281 (29.3)
 Below degree qualification 10,866 (50.7)
 No qualification 4303 (20.1)
National Statistics Socio-economic Classification (NS-SEC)
 Managerial and professional occupations 9387 (43.7)
 Intermediate occupations 2384 (11.1)
 Small employers and own account workers 2366 (11.0)
 Lower supervisory and technical occupations 1738 (8.1)
 Semi-routine occupations 5135 (23.9)
 Other 447 (2.1)
Body Mass Index (BMI)
 Not overweight or obese 6502 (33.6)
 Overweight 7223 (37.4)
 Obese 5602 (29.0)
Self-reported general health
 Very good or good 15,803 (73.6)
 Fair 4010 (18.7)
 Bad or very bad 1658 (7.7)
Smoking status
 Current cigarette smoker 2546 (11.9)
 Ex-regular cigarette smoker 6356 (29.6)
 Never regular cigarette smoker 12,536 (58.5)

Percentage with total hypertension and undiagnosed hypertension by characteristics

Table 2, Table 3 present the percentage of men and women with hypertension and undiagnosed hypertension by characteristics. Among all men, 34.3% (95% confidence interval 33.2–35.4) had hypertension and 30.7% (29.0–32.4) of those were undiagnosed. Among all women, 29.7% (28.8–30.7) had hypertension and 27.6% (26.1–29.1) of those were undiagnosed.

Table 2.

Percentage with hypertension and undiagnosed hypertension by characteristics–females.

Total hypertension (among all females)
Undiagnosed hypertension (among females with hypertension)
Weighted N Percentage (95% CI) Weighted N Percentage (95% CI)
Total 10,890 29.7 (28.8–30.7) 3770 27.6 (26.1–29.1)
Age group
 16–24 years 1350 4.0 (2.4–5.6) 60 26.1 (8.0–44.3)
 25–34 years 1740 7.9 (6.3–9.5) 160 44.0 (33.3–54.6)
 35–44 years 1670 13.6 (11.9–15.3) 270 34.0 (27.6–40.3)
 45–54 years 1880 25.9 (23.8–27.9) 570 31.0 (27.0–35.0)
 55–64 years 1600 40.0 (37.8–42.3) 740 29.1 (25.8–32.4)
 65–74 years 1430 57.8 (55.6–60.1) 960 26.8 (24.2–29.5)
 75 years and over 1220 71.2 (68.9–73.5) 1010 21.1 (18.6–23.5)
Ethnicity
 White 9390 28.6 (27.3–29.8) 3400 22.3 (20.7–24.1)
 Black 360 46.2 (39.9–52.6) 130 16.1 (10.7–23.6)
 Asian 880 31.9 (26.8–37.4) 190 26.1 (18.8–34.9)
 Other 260 30.8 (23.1–39.8) 50 15.3 (8.2–26.8)
Region
 North East 530 31.1 (28.0–34.4) 210 22.2 (18.3–26.7)
 North West 1430 31.3 (28.4–34.3) 510 21.4 (18.3–25.0)
 Yorkshire and the Humber 1070 29.8 (26.5–33.4) 360 19.0 (15.2–23.4)
 East Midlands 910 33.1 (30.1–36.2) 360 24.7 (20.8–29.0)
 West Midlands 1120 31.4 (28.1–34.8) 420 20.7 (16.8–25.1)
 East of England 1200 28.1 (25.5–30.8) 440 21.6 (18.1–25.6)
 London 1590 28.5 (25.2–32.1) 410 21.0 (16.6–26.3)
 South East 1850 26.6 (24.4–29.0) 620 22.9 (19.7–26.4)
 South West 1180 28.3 (25.4–31.4) 440 26.0 (22.1–30.4)
Rural-urban classification
 Urban 8780 29.9 (28.6–31.2) 2940 21.6 (19.8–23.4)
 Rural 2110 27.6 (25.4–29.8) 830 24.6 (21.6–27.8)
Relationship status
 Single 2130 33.6 (30.2–37.3) 330 17.1 (13.5–21.4)
 Married or civil partnership 5420 28.4 (26.8–30.1) 2040 24.4 (22.1–26.9)
 Cohabiting 1400 27.3 (24.1–30.8) 250 22.3 (17.6–27.9)
 Separated or divorced 1030 29.1 (26.5–31.9) 460 21.9 (18.3–25.9)
 Widowed or surviving partner 910 31.2 (27.8–34.7) 700 19.7 (16.3–23.7)
Educational qualifications
 Degree or equivalent qualification 3200 23.6 (21.9–25.5) 670 26.2 (23.0–29.6)
 Below degree qualification 5580 30.1 (28.6–31.6) 1860 22.2 (20.2–24.4)
 No qualification 2090 35.5 (32.8–38.3) 1230 18.6 (16.0–21.7)
Socio-economic status (NS-SEC)
 Managerial and professional occupations 4390 25.6 (24.1–27.2) 1290 25.0 (22.6–27.6)
 Intermediate occupations 1340 30.6 (27.9–33.5) 550 21.2 (17.8–25.0)
 Small employers and own account workers 1150 24.4 (21.7–27.4) 340 27.4 (22.7–32.5)
 Lower supervisory and technical occupations 810 31.1 (27.6–34.9) 280 21.1 (16.6–26.4)
 Semi-routine occupations 2810 35.5 (33.3–37.8) 1180 18.7 (16.4–21.3)
 Other 360 38.2 (30.5–46.6) 120 19.2 (11.8–29.7)
Body Mass Index (BMI)
 Not overweight or obese 4000 17.8 (16.3–19.3) 780 24.9 (21.7–28.4)
 Overweight 3090 26.7 (24.9–28.5) 1100 24.1 (21.4–27.0)
 Obese 2730 43.9 (41.6–46.2) 1390 20.5 (18.2–22.9)
Self-reported general health
 Very good or good 8150 25.3 (24.1–26.5) 2260 27.5 (25.4–29.8)
 Fair 1910 39.6 (37.0–42.4) 1020 14.4 (12.4–16.7)
 Bad or very bad 830 45.3 (41.1–49.5) 500 13.9 (11.1–17.4)
Cigarette smoking status
 Current cigarette smoker 1400 29.6 (26.5–32.8) 380 22.2 (18.3–26.6)
 Ex-regular cigarette smoker 2550 30.7 (28.7–32.8) 1140 20.7 (18.3–23.4)
 Never regular cigarette smoker 6910 29.0 (27.7–30.5) 2260 23.3 (21.3–25.5)

CI – confidence interval. All estimates are weighted, and all are age-adjusted except where the predictor is age or where there is no predictor (i.e., total population estimates). Weighted sample sizes are rounded to the nearest 10. Base population for total hypertension is all females; base population for undiagnosed hypertension is females with hypertension.

Table 3.

Percentage with hypertension and undiagnosed hypertension by characteristics–males.

Total hypertension (among all males)
Undiagnosed hypertension (among males with hypertension)
Weighted N Percentage (95% CI) Weighted N Percentage (95% CI)
Total 10,590 34.3 (33.2–35.4) 4220 30.7 (29.0–32.4)
Age group
 16–24 years 1470 6.9 (4.6–9.2) 120 66.2 (49.9–82.5)
 25–34 years 1740 12.7 (10.6–14.9) 260 55.3 (46.3–64.2)
 35–44 years 1680 22.0 (19.6–24.4) 430 44.1 (37.8–50.4)
 45–54 years 1810 34.7 (32.1–37.3) 730 35.0 (30.5–39.5)
 55–64 years 1610 51.8 (49.2–54.5) 970 29.1 (25.9–32.3)
 65–74 years 1330 63.7 (61.4–66.0) 980 23.0 (20.4–25.6)
 75 years and over 960 65.9 (63.3–68.6) 730 16.6 (14.2–19.0)
Ethnicity
 White 9140 37.6 (36.3–39.0) 3820 34.6 (32.3–36.9)
 Black 270 48.1 (37.1–59.2) 110 40.6 (28.6–53.8)
 Asian 880 33.1 (28.3–38.3) 220 31.1 (23.8–39.4)
 Other 280 36.6 (27.2–47.1) 70 24.7 (12.6–42.6)
Region
 North East 530 39.1 (35.3–43.0) 230 34.1 (28.3–40.5)
 North West 1350 43.6 (40.0–47.3) 620 36.8 (31.7–42.1)
 Yorkshire and the Humber 1010 38.8 (34.9–42.9) 420 35.1 (29.4–41.2)
 East Midlands 890 37.8 (34.4–41.4) 370 39.6 (34.0–45.6)
 West Midlands 1140 38.9 (35.2–42.7) 470 34.3 (28.8–40.3)
 East of England 1230 35.7 (32.6–38.9) 480 30.6 (25.8–35.9)
 London 1590 36.4 (32.4–40.6) 510 25.9 (20.5–32.2)
 South East 1750 33.4 (30.7–36.2) 650 36.1 (31.6–40.9)
 South West 1090 36.6 (32.6–40.8) 470 37.4 (32.0–43.0)
Rural-urban classification
 Urban 8580 37.7 (36.3–39.2) 3310 32.3 (30.0–34.6)
 Rural 2000 36.7 (33.9–39.5) 920 41.9 (37.8–46.1)
Relationship status
 Single 2610 43.6 (39.9–47.4) 600 36.9 (31.8–42.2)
 Married or civil partnership 5570 35.2 (33.6–36.8) 2590 32.7 (30.0–35.5)
 Cohabiting 1460 36.3 (32.7–40.1) 410 38.9 (32.7–45.4)
 Separated or divorced 610 41.4 (37.2–45.7) 360 30.1 (24.7–36.0)
 Widowed or surviving partner 330 42.5 (37.1–48.2) 260 38.1 (31.0–45.7)
Educational qualifications
 Degree or equivalent qualification 3250 32.5 (30.4–34.7) 1050 35.0 (31.2–39.0)
 Below degree qualification 5520 38.6 (36.9–40.4) 2140 34.9 (32.1–37.7)
 No qualification 1800 42.3 (39.5–45.2) 1030 31.8 (28.0–35.9)
Socio-economic status (NS-SEC)
 Managerial and professional occupations 4590 34.9 (33.0–36.7) 1710 34.9 (32.1–37.9)
 Intermediate occupations 970 36.6 (32.4–41.1) 370 34.8 (28.6–41.5)
 Small employers and own account workers 1310 37.8 (34.3–41.3) 570 37.6 (32.5–42.9)
 Lower supervisory and technical occupations 930 36.4 (32.7–40.3) 380 31.9 (26.7–37.6)
 Semi-routine occupations 2500 43.5 (40.8–46.3) 1150 32.5 (28.9–36.4)
 Other 270 33.2 (22.8–45.7) 60 30.2 (14.1–53.4)
Body Mass Index (BMI)
 Not overweight or obese 3160 24.0 (21.9–26.2) 660 43.5 (38.1–49.2)
 Overweight 3950 34.9 (33.1–36.8) 1600 35.8 (32.7–39.1)
 Obese 2570 52.6 (50.0–55.2) 1520 30.0 (26.9–33.3)
Self-reported general health
 Very good or good 8160 33.7 (32.3–35.2) 2720 41.0 (38.4–43.6)
 Fair 1750 46.2 (43.4–49.1) 1010 21.3 (18.2–24.8)
 Bad or very bad 680 55.5 (50.8–60.1) 490 18.3 (14.4–23.1)
Cigarette smoking status
 Current cigarette smoker 1560 40.1 (36.6–43.8) 540 37.0 (31.5–42.8)
 Ex-regular cigarette smoker 2960 40.0 (38.0–42.1) 1620 29.5 (26.6–32.6)
 Never regular cigarette smoker 6020 35.6 (33.9–37.3) 2060 36.5 (33.7–39.3)

CI – confidence interval. All estimates are weighted, and all are age-adjusted except where the predictor is age or where there is no predictor (i.e., total population estimates). Weighted sample sizes are rounded to the nearest 10. Base population for total hypertension is all males; base population for undiagnosed hypertension is males with hypertension.

Hypertension prevalence increased with age, however, among those with hypertension, younger adults were more likely to be undiagnosed. The groups with the highest proportion undiagnosed were 16–24-year-old men (66.2% (95% confidence interval 49.9–82.6)) and 25–34-year-old women (44.0% (33.3–55.6)). This compared to 16.6% (14.2–19.0%) of men and 21.1% (18.6–23.5%) of women aged 75 and over.

For ethnicity, age-adjusted hypertension prevalence was highest among women who belonged to the Black ethnic group. There were no differences in hypertension prevalence by ethnicity for men, nor in the proportion who were undiagnosed for either men or women.

Men living in the North West of England and women living in the East Midlands had the highest age-adjusted hypertension prevalence, and men and women in the South East had the lowest prevalence. There were no differences in the proportion of women who were undiagnosed by region, but for men the highest proportion undiagnosed was in the East Midlands (39.6% (95% confidence interval 34.0–45.6)) and the lowest in London (25.9% (20.5–32.2)) and the East of England (30.6% (25.8–35.9)). Men living in rural areas were also more likely to be undiagnosed (41.9% (37.8–46.1)) than those living in urban areas (32.3% (30.0–34.6)).

Age-adjusted hypertension prevalence was highest among men and women in ‘semi-routine occupations’ and lowest among men and women in ‘managerial and professional occupations’ and women working for ‘small employers and own account workers’. For women, the highest percentage undiagnosed was among ‘small employers and own account workers’ (27.4% (95% confidence interval 22.7–32.5)) and ‘managerial and professional occupations’ (25.0% (22.6–27.6%) and the lowest among ‘semi-routine occupations’ (18.7% (16.4–21.3)), while there were no differences in the proportion undiagnosed by NS-SEC for men.

Men and women with no educational qualifications had the highest age-adjusted hypertension prevalence and those with degree-level or equivalent qualifications had the lowest prevalence. For women, the highest percentage undiagnosed was among those with degree-level or higher qualifications (26.2% (95% confidence interval 23.0–30.0)) and the lowest was among those with no qualifications (18.6% (16.0–21.7)), while there were no differences in the proportion of men undiagnosed by education.

Men and women who were single had the highest age-adjusted hypertension prevalence and those who were married or in a civil partnership had the lowest prevalence. For women, the highest percentage undiagnosed was among those who were married or in a civil partnership (24.4% (95% confidence interval 22.1–26.9)) and the lowest was among those who were single (17.1% (13.5–21.4)), while there were no differences by relationship status for men.

Age-adjusted hypertension prevalence was highest among men and women whose self-reported general health was ‘bad or very bad’ and lowest among those whose health was ‘very good or good’. However, among those with hypertension, adults whose health was ‘very good or good’ were the most likely to be undiagnosed (men 41.0% (95% confidence interval 38.4–43.6%), women 27.5% (25.4–29.8)) and those whose health was ‘bad or very bad’ were the least likely to be undiagnosed (men 18.3% (14.4–23.1%), women 13.9% (11.1–17.4)).

Men and women in the obese BMI category had the highest age-adjusted hypertension prevalence and those classified as not overweight or obese had the lowest prevalence. However, among those with hypertension, individuals classified as not overweight or obese were the most likely to be undiagnosed (men 43.5% (95% confidence interval 38.1–49.2%), women 24.9% (21.7–28.4)) and those classified as obese were the least likely (men 30.0% (26.9–33.3)), women 20.1% (18.2–22.9)).

Men who were ex-regular smokers were the most likely to have hypertension and those who had never regularly smoked were the least likely, however, among men with hypertension, those who had never regularly smoked were the most likely to be undiagnosed (36.5% (95% confidence interval 33.7–39.3)) and ex-regular smokers were the least likely (29.5% (26.6–32.6)). There were no differences in prevalence of hypertension or undiagnosed hypertension by smoking status for women.

Regression models

In fully adjusted models, age, BMI, and self-reported general health were independently associated with the likelihood of men and women with hypertension being undiagnosed after adjusting for sociodemographic characteristics (see Table 4). Compared with those aged 75 years and over, the age groups with the highest odds of being undiagnosed were 16–24-year-old men (odds ratio (OR) 8.5 (95% confidence interval 3.9–18.7)) and 25–34-year-old women (2.8 (1.7–4.5)). Men and women who were not classified as overweight or obese according to their BMI had 1.9 (1.4–2.4) and 1.2 (1.0–1.5) times the odds of being undiagnosed, respectively, compared with those who were classified as obese. Men and women whose self-reported general health was ‘very good or good’ had 3.5 (2.5–4.8) and 2.2 (1.7–2.9) times the odds of being undiagnosed compared with those whose self-reported general health was ‘bad or very bad’.

Table 4.

Adjusted odds ratios for undiagnosed hypertension, among those with hypertension, by characteristics.

Males
Females
Minimally adjusted model Fully adjusted model Minimally adjusted model Fully adjusted model
Age group
 16–24 years 9.84 (4.60–21.04) 8.52 (3.89–18.67) 1.32 (0.51–3.43) 1.43 (0.53–3.90)
 25–34 years 6.19 (4.13–9.28) 6.10 (3.91–9.50) 2.94 (1.86–4.64) 2.75 (1.66–4.54)
 35–44 years 3.96 (2.90–5.40) 4.15 (2.95–5.83) 1.93 (1.40–2.65) 1.70 (1.18–2.43)
 45–54 years 2.70 (2.07–3.51) 2.79 (2.09–3.73) 1.68 (1.33–2.13) 1.48 (1.12–1.95)
 55–64 years 2.06 (1.63–2.60) 2.14 (1.66–2.76) 1.53 (1.24–1.91) 1.32 (1.04–1.69)
 65–74 years 1.50 (1.20–1.87) 1.52 (1.21–1.91) 1.37 (1.12–1.68) 1.27 (1.02–1.57)
 75 years and over Reference Group
Ethnicity
 Black 1.25 (0.73–2.13) 1.53 (0.86–2.75) 0.69 (0.42–1.11) 0.80 (0.48–1.31)
 Asian 0.87 (0.59–1.27) 1.11 (0.74–1.65) 1.25 (0.81–1.93) 1.24 (0.80–1.93)
 Other 0.68 (0.31–1.47) 0.75 (0.37–1.53) 0.65 (0.32–1.32) 0.67 (0.32–1.40)
 White Reference Group
Region
 North East 0.77 (0.54–1.09) 0.79 (0.55–1.13) 0.88 (0.64–1.21) 0.87 (0.64–1.20)
 North West 0.88 (0.64–1.21) 0.92 (0.66–1.28) 0.84 (0.63–1.12) 0.83 (0.61–1.11)
 Yorkshire and the Humber 0.81 (0.58–1.15) 0.85 (0.60–1.20) 0.72 (0.52–1.01) 0.70 (0.50–0.98)
 West Midlands 0.80 (0.57–1.12) 0.82 (0.58–1.17) 0.81 (0.59–1.12) 0.81 (0.59–1.12)
 East of England 0.67 (0.48–0.94) 0.63 (0.45–0.88) 0.85 (0.63–1.15) 0.81 (0.60–1.10)
 London 0.54 (0.37–0.78) 0.56 (0.39–0.83) 0.85 (0.59–1.21) 0.82 (0.57–1.18)
 South East 0.86 (0.64–1.17) 0.86 (0.63–1.17) 0.92 (0.70–1.22) 0.88 (0.66–1.17)
 South West 0.89 (0.64–1.25) 0.83 (0.59–1.17) 1.07 (0.79–1.43) 1.01 (0.75–1.36)
 East Midlands Reference Group
Rural-urban classification
 Rural 1.50 (1.24–1.81) 1.47 (1.21–1.79) 1.17 (0.98–1.39) 1.07 (0.89–1.29)
 Urban Reference Group
Relationship status
 Married or civil partnership 0.85 (0.65–1.09) 0.81 (0.62–1.05) 1.61 (1.17–2.22) 1.43 (1.04–1.98)
 Cohabiting 1.09 (0.76–1.56) 1.03 (0.71–1.49) 1.45 (0.97–2.16) 1.34 (0.90–2.00)
 Separated or divorced 0.75 (0.53–1.05) 0.74 (0.52–1.04) 1.41 (0.98–2.03) 1.37 (0.95–1.97)
 Widowed or surviving partner 1.11 (0.76–1.61) 1.08 (0.74–1.59) 1.19 (0.82–1.73) 1.17 (0.80–1.69)
 Single Reference Group
Educational qualifications
 Degree or equivalent qualification 1.15 (0.90–1.47) 1.13 (0.86–1.48) 1.56 (1.21–2.02) 1.37 (1.05–1.79)
 Below degree qualification 1.14 (0.94–1.40) 1.10 (0.89–1.36) 1.26 (1.03–1.53) 1.18 (0.97–1.44)
 No qualification Reference Group
Socio-economic status (NS-SEC)
 Managerial and professional occupations 1.13 (0.92–1.39) 1.12 (0.89–1.41) 1.42 (1.17–1.72) 1.23 (1.00–1.52)
 Intermediate occupations 1.12 (0.81–1.55) 1.11 (0.78–1.57) 1.14 (0.89–1.46) 1.09 (0.84–1.41)
 Small employers and own account workers 1.26 (0.97–1.66) 1.28 (0.97–1.68) 1.62 (1.24–2.13) 1.45 (1.09–1.92)
 Lower supervisory and technical occupations 0.99 (0.74–1.33) 1.01 (0.75–1.36) 1.15 (0.83–1.58) 1.08 (0.78–1.51)
 Other 0.96 (0.38–2.45) 1.05 (0.46–2.41) 1.06 (0.59–1.88) 1.16 (0.66–2.02)
 Semi-routine occupations Reference Group
Body Mass Index (BMI)
 Not overweight or obese 1.78 (1.38–2.29) 1.86 (1.44–2.40) 1.28 (1.04–1.58) 1.24 (1.00–1.53)
 Overweight 1.30 (1.08–1.56) 1.30 (1.08–1.58) 1.23 (1.02–1.47) 1.20 (1.00–1.44)
 Obese Reference Group
Self-reported general health
 Very good or good 3.11 (2.30–4.20) 3.46 (2.52–4.75) 2.32 (1.79–3.02) 2.21 (1.70–2.87)
 Fair 1.21 (0.86–1.70) 1.29 (0.91–1.82) 1.02 (0.76–1.38) 1.00 (0.75–1.35)
 Bad or very bad Reference Group
Cigarette smoking status
 Ex-regular cigarette smoker 0.72 (0.55–0.94) 0.71 (0.54–0.93) 0.93 (0.70–1.23) 0.84 (0.63–1.11)
 Never regular cigarette smoker 0.98 (0.75–1.27) 0.95 (0.73–1.24) 1.07 (0.82–1.40) 0.95 (0.73–1.24)
 Current cigarette smoker Reference Group

Estimates are odds ratios with 95% confidence intervals in brackets. Minimally adjusted models were adjusted for age group and stratified by sex. Fully adjusted models were adjusted for age group, ethnicity, region, rural-urban classification, relationship status, highest educational qualification, and NS-SEC, and stratified by sex.

Among men with hypertension, other characteristics that were independently associated with the likelihood of being undiagnosed were rural-urban classification (rural OR 1.5 (95% confidence interval 1.2–1.8) compared with urban), region (London 0.6 (0.4–0.8), East of England 0.6 (0.5–0.9) compared with East Midlands), and smoking status (ex-regular smokers 0.7 (0.5–0.9) compared with current smokers). Among women with hypertension, other characteristics that were independently associated with the likelihood of being undiagnosed were NS-SEC (‘small employers and own account workers’ 1.5 (1.1–1.9), ‘managerial and professional occupations’ 1.2 (1.0–1.5) compared with ‘semi-routine occupations’), educational qualifications (degree-level qualification or equivalent 1.4 (1.1–1.8) compared with no qualification), and relationship status (married or in a civil partnership 1.4 (1.0–2.0) compared with single).

Discussion

The findings of this study show that many of the groups who were less likely to have hypertension, such as younger adults and those with a lower BMI, were more likely to be undiagnosed if they did have hypertension. Our finding that 30.7% of men and 27.6% of women with hypertension were undiagnosed aligns with previous estimates in England,10 and provides further evidence for the substantial burden of undiagnosed hypertension, which is likely to have further increased since the COVID-19 pandemic.12,13 Our findings suggest that current approaches to hypertension detection are targeting those most at risk, but also indicate that considerable numbers of young and otherwise healthy individuals have undiagnosed hypertension. Given the high lifetime risk of hypertension and its strong links with morbidity and mortality,1,2 our results suggest a need for greater awareness of the potential for undiagnosed hypertension among all groups, including those considered “low risk”. This will be especially important if the government is to achieve its ambition of diagnosing 80% of hypertension cases in England by 2029.11

Individuals with known hypertension risk factors (such as older adults and those in poor health) are likely to have more frequent contact with healthcare services, providing greater opportunity for blood pressure measurement. Those with known risk factors may also be more likely to have their blood pressure opportunistically measured during routine healthcare appointments. In our analysis, men and younger adults were more likely to be undiagnosed than women and older adults, which aligns with previous research.16,17 In 2019, 69% of men in England reported having consulted with a GP in the previous 12 months, compared with 82% of women, and sex differences were greater among younger adults.5 Women are more likely to have routine healthcare appointments where blood pressure is measured, for example during oral contraceptive check-ups or during pregnancy or post-natal healthcare checks. However, research has shown that men have fewer healthcare consultations than women even after accounting for reproductive-related contacts.19 This suggests that relying solely on contact with healthcare services for hypertension detection is likely to systematically overlook certain groups of the population, including young men.

Better self-reported general health and a lower BMI were associated with an increased likelihood of hypertension being undiagnosed. This is likely due to the relationships between general health, BMI and a variety of long-term health conditions and may therefore be related to frequency of contact with healthcare services or the likelihood of opportunistic blood pressure measurement taking place during those contacts. However, individuals with a diagnosis of hypertension may factor this into self-reports of their general health and reverse causality or a bidirectional relationship is likely. That is to say that individuals who are otherwise in good health may be less likely to have their hypertension diagnosed, but individuals who do not know they have hypertension may also be more likely to self-report their health as good.

Men who lived in London and the East of England, and those who lived in urban areas, were less likely to be undiagnosed than those living in other regions or in rural areas. A previous study found that rates of hypertension diagnosis were lower among people living in rural areas in low- and middle-income countries but not in high-income countries, although the analysis was not disaggregated by sex.19 Our findings suggest that convenience of access to healthcare may be a significant factor for hypertension diagnosis among men.

Among women, additional factors that were associated with a higher likelihood of hypertension being undiagnosed were being more highly educated, being married or in a civil partnership, and belonging to the NS-SEC classes ‘managerial and professional occupations’ or ‘small employers or own account workers’. Individuals who are more highly educated and those who belong to higher socioeconomic classes have better health on average than those who are less educated or who belong to lower socioeconomic classes,20,21 and may therefore have reduced opportunity for blood pressure monitoring as part of routine healthcare. However, in our analysis, education and NS-SEC were only associated with undiagnosed hypertension for women. Analysis of primary care data in the UK found a deprivation gradient in healthcare use among women whereby those in more deprived areas had higher rates of GP consultations than women in less deprived areas, but no difference was found for men,22 which may explain our findings. Women with higher levels of education also have fewer children on average,23 and differences in reproductive-related healthcare contacts may add to the deprivation effect for women. The difference in undiagnosed hypertension by marital status among women is unexpected and warrants further investigation.

The Health Survey for England (HSE) provided a unique opportunity to explore inequalities in undiagnosed hypertension. The rigorous survey design and weighting methods enabled us to produce estimates of undiagnosed hypertension for a representative sample of adults in England. The survey benefits from stringent blood pressure protocols designed to optimise the accuracy of readings. Nonetheless, our study had limitations. Firstly, despite efforts to boost sample size by pooling data from multiple years, limitations arose from small numbers with hypertension in some predictor groups. This was a particular issue for ethnicity, which led to wide confidence intervals for the “Black”, “Asian”, and “Other” ethnic groups, especially for men. This may explain why we found little evidence for differences in hypertension prevalence by ethnicity for men, despite previous literature demonstrating higher prevalence among Black men as well as Black women.15 Secondly, our analysis used self-reports of hypertension which will not fully align with clinical diagnoses. Research on self-reports of hypertension offer mixed evidence for their accuracy,24,25 but some suggest underestimation compared to clinical records, which would imply overestimation of undiagnosed hypertension in our analysis. However, this would only impact the interpretation of our findings if the level of disagreement varied across groups. Other studies use self-reports of anti-hypertensive medication instead of self-reports of diagnosis,5,26 however this excludes individuals with hypertension controlled by lifestyle interventions. Blood pressure measurements taken at a single point in time are not equivalent to a diagnosis of hypertension, which requires 24-h ambulatory or at-home blood pressure monitoring.9 Because the HSE cannot show individual variability in blood pressure over time, there is potential for low reproducibility of measurements and over-estimation of undiagnosed hypertension. Again, this would only impact interpretation of our findings if conversion of single-point-in-time measurements to clinical diagnoses differed between groups. Finally, there are limitations associated with the study design, including the cross-sectional design which means we cannot make inferences about causal relationships or rule out the possibility of reverse causality, and the potential for unmeasured confounding in our analysis.

In England, blood pressure checks are offered every five years to adults aged 40–75 under the NHS Health Check, and 1 in 34 Health Check attendees are diagnosed with hypertension, but the programme had an uptake of just 53% between 2012 and 2017 and this further reduced to 40% in 2021/22.27,28 There is substantial regional disparity in uptake, ranging from 25% to 85%, as well as differences by demographic factors such as sex (higher uptake among females) and age (higher uptake among older adults). Since 2021, free blood pressure checks for adults over the age of 40 have also been available at community pharmacies. Our findings demonstrate that, despite these programmes, undiagnosed hypertension remains prevalent among the adult population of England and affects groups who are not typically covered by existing screening or identification methods. Early identification and intervention are associated with better health and economic outcomes,2,3 and there may be substantial benefit in ensuring accessibility of hypertension screening for all groups, including young adults and those who are not routinely in contact with healthcare services. Nonetheless, further research is needed to understand the impact of extending hypertension screening to these groups and identify the most effective methods for providing screening to those who are not already in contact with healthcare services. A 2015 systematic review emphasised the potential of community-based, non-physician or self-screening methods to improve detection of hypertension,29 however, a recent Cochrane review highlighted the need for additional high-quality evidence on the effectiveness of different screening strategies in reducing hypertension-related morbidity and mortality.30

This study builds on the evidence for the substantial burden of undiagnosed hypertension in England and provides evidence that some of the groups who are less likely to have hypertension (such as younger adults and those with a lower BMI) are the most likely to be undiagnosed if they do have hypertension. Given the high lifetime risk of hypertension, its strong associations with morbidity and mortality, and the health and economic benefits of early identification and intervention,1, 2, 3, 4 our findings suggest a need for greater awareness of the risks of undiagnosed hypertension, including among those typically considered “low risk”.

Contributors

KF, VN and CS conceived the idea for the study. Study design was led by KF and EC with input from CS and VN. EC was responsible for curating and cleaning the data, and analysis was carried out by EC, EM, KF, and NCC. KF and CS had leadership responsibility and supervised the project. Methodological advice was provided by VN, PP and IW. AH, VR and AB provided topic expertise and contributed to validation of methods and findings. KF, EC and EM wrote the first draft of the publication. All authors reviewed and commented on the publication and approved the final version. KF, EC and EM accessed and verified the underlying data.

Data sharing statement

Data from the Health Survey for England is available for researchers to access via the UK Data Service.

Declaration of interests

AB has received research grant funding from the National Institute for Health Research (NIHR), British Medical Association, AstraZeneca, and UK Research and Innovation. All other authors declare no competing interests.

Acknowledgements

AB is chief investigator of the NIHR-funded STIMULATE-ICP programme [NIHR COV-LT2-0043].

Footnotes

Appendix A

Supplementary data related to this article can be found at https://doi.org/10.1016/j.eclinm.2023.102275.

Appendix A. Supplementary data

Supplementary material
mmc1.docx (85KB, docx)

References

Associated Data

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Supplementary Materials

Supplementary material
mmc1.docx (85KB, docx)

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