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Original research
Trends of mean systolic and diastolic blood pressure among adults in Shenzhen, China, 1997–2018: findings from three rounds of the population-based survey
  1. Ke Peng1,
  2. Weicong Cai2,3,
  3. Xiaoying Liu1,
  4. Yishu Liu4,
  5. Menglu Ouyang5,6,
  6. Jessica Gong7,
  7. Zhihui Wang8,
  8. Yunfeng Wang1,9,
  9. Jing Hao10,
  10. Wei Wang11,
  11. Honglei Zhao1,
  12. Kaihao Lin2,
  13. Guiyuan Han1,
  14. Yu Shi1,
  15. Yinghao Xie1,12,
  16. Yuxin Xie1,12,
  17. Lin Lei2,
  18. Lei Si13
  1. 1Fuwai Hospital Chinese Academy of Medical Sciences, Shenzhen, Guangdong, China
  2. 2Shenzhen Center for Chronic Disease Control, Shenzhen, Guangdong, China
  3. 3University of New South Wales, Sydney, New South Wales, Australia
  4. 4The George Institute for Global Health, Beijing, China
  5. 5The George Institute for Global Health, Newtown, New South Wales, Australia
  6. 6George Institute for China at Peking University Health Science Center, Beijing, China
  7. 7Imperial College London, London, UK
  8. 8Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
  9. 9National Center for Cardiovascular Diseases, Beijing, China
  10. 10Shenzhen Mindray Bio-Medical Electronic Co, Shenzhen, China
  11. 11National Center for Chronic and Noncommunicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
  12. 12University of South China, Hengyang, China
  13. 13Western Sydney University, Penrith South, New South Wales, Australia
  1. Correspondence to Dr Lin Lei; lin.leilana{at}gmail.com

Abstract

Objective To quantify the trends in systolic and diastolic blood pressure (BP) among adults in Shenzhen from 1997 to 2018.

Design Cross-sectional study.

Settings The data were collected from all districts in Shenzhen, China in the years of 1997, 2009 and 2018 by multistage cluster sampling procedure.

Participants Participants were residents aged 18–69 years in Shenzhen, China. A total of 26 621 people were included: 8266 people in 1997, 8599 people in 2009 and 9756 people in 2018.

Primary and secondary outcome measures All participants were surveyed about their sociodemographic and lifestyle information. BP was measured by trained physicians using a mercury sphygmomanometer. Hypertension was defined as systolic BP of at least 140 mm Hg and diastolic BP of at least 90 mm Hg, self-reported use of antihypertensive medications or both. Hypertension control was defined as systolic BP values of less than 140 mm Hg and diastolic BP values of less than 90 mm Hg.

Result Age-adjusted mean systolic BP increased from 117±16 mm Hg to 123±15 mm Hg (p<0.001) in males, and from 113±18 mm Hg to 115±16 mm Hg (p<0.001) in females from 1997 to 2018. Diastolic BP among males increased from 75 mm Hg (SD=11) to 79 mm Hg (SD=11) and increased from 71 mm Hg (SD=10) to 73 mm Hg (SD=10) among females between 1997 and 2018 (p<0.001). Rate of hypertension rose rapidly from 17.71% (95% CI: 16.60% to 18.90%) in 2009 to 24.01% (95% CI: 22.84% to 25.22%) in 2018 among males (p<0.001), whereas the prevalence among females remained stable at around 13.5% (p=0.98). Both awareness and treatment rates of hypertension among males and females showed a decreased trend between 2009 and 2018, while no significant changes were observed for control rates.

Conclusions The mean systolic BP and diastolic BP among adults in Shenzhen increased from 1997 to 2018, and no improvements in hypertension awareness, treatment and control rates were found.

  • Hypertension
  • Blood Pressure
  • EPIDEMIOLOGY

Data availability statement

Data are available upon reasonable request.

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STRENGTHS AND LIMITATIONS OF THIS STUDY

  • This study used three large representative samples to illustrate the trend of blood pressure (BP) in the last 20 years and changes of prevalence, awareness, treatment and control in the last decade among adults in Shenzhen.

  • All measurements in this survey have passed a standardisation and certification programme besides the large sample size.

  • This is a cross-sectional study; hence, no causal or temporal inferences between potential risk factors and hypertension can be determined.

  • Out-of-office BP is not available, so hypertension was defined by office BP and self-reported medical history, which may result in recall bias and reporting bias.

  • The study population were all recruited from Shenzhen, which is a city of immigration with a rapid turnover of residents; thus, representativeness and generalisability were of concern.

Background

Hypertension or elevated blood pressure (BP) is one of the major risk factors for cardiovascular diseases (CVDs), which represents a significant public health concern in China. The estimated number of patients with CVD was 330 million in 2019, among which 245 million individuals were found to have hypertension.1

China’s rapid economic development and healthcare system reforms have greatly ameliorated people’s living environments, lifestyles and accessibility to healthcare services. As a result, overall health and life expectancy have improved substantially, although the population is ageing.2 3 In 2009, the Chinese government launched the healthcare reform2 and the China Essential Public Health Service policy, which aimed to provide affordable and equitable care for diabetes and hypertension.3 Since then, the management of hypertension has been improved due to the benefits package to treat hypertension and the transition of hypertension programmes from institutional service to community care.3 However, gaps including accessibility to patient-centred treatment and primary prevention still exist when compared with high-income countries.3 The current Chinese guidelines for hypertension management with the threshold for diagnosing hypertension of 140 mm Hg for systolic BP (SBP) and 90 mm Hg for diastolic BP (DBP) are implemented in China4; however, there is an appeal to lower the threshold for diagnosing hypertension to 130 mm Hg for SBP and 80 mm Hg for DBP, based on findings from a large-scale randomised controlled trial in the Chinese population.5 6 This proposed change could potentially complicate the implementation of hypertension management strategies.

As the first Special Economic Zone in China, Shenzhen is an iconic model of China’s rapid development since the implementation of the reform and opening up policies in the 1980s. Along with the rapid development in Shenzhen, it also faced challenges including an increased burden of CVDs. It was reported that the prevalence of CVD risk factors in Shenzhen was worse when compared with the national average.7 Notably, over 70% of the Shenzhen residents are migrants,8 and most of these migrants are younger. Even though the prevalence of hypertension among Shenzhen residents was lower than the national average, such populations were reported to be more likely to have low awareness of hypertension9 and lifestyle risk factors such as physical inactivity10 and unhealthy diet.11 Moreover, migrant workers may not be covered by local or other health insurance schemes, they are more likely to spend out-of-pocket health expenditures12 and may not receive proper treatment due to high cost.

Given the frequent turnover of the migrant population and the implementation of several health-related policies in Shenzhen, it is crucial to monitor CVD risk factors for adequate policy adaptations. However, the evidence on the whole population throughout different time epochs is lacking. This study aimed to analyse the trends of SBP and DBP among Shenzhen residents, including three population-based cross-sectional studies in 1997, 2009 and 2018.

Methods

Study design and participants

Three population-based cross-sectional surveys were conducted in Shenzhen in 1997, 2009 and 2018, using a multistage, stratified, cluster randomised sampling design. These studies were designed to determine the prevalence of non-communicable diseases and their risk factors among community dwellers in Shenzhen. Participants from the randomly selected families who provided written informed consent for participation were invited and included, but those who live in functional areas, such as temporary sheds and nursing homes, were excluded. A pre-established replacement procedure was adopted to recruit substitutes for non-respondents.

In 1997, we randomly selected one or two blocks/towns from five administrative districts (three urban and two rural) in Shenzhen. Then, one or two communities/villages were randomly selected from each block/town, yielding a total of 16 communities/villages, followed by a survey conducted among residents aged 18–69 years who lived in Shenzhen for at least 6 months in the past 12 months from each household.

In 2009, in seven administrative districts, we randomly selected 34 subdistricts using the proportional probability sampling method. A total of 120 households from 72 communities were randomly selected from included streets. A Kish grid was adopted to recruit residents aged 18–69 years who lived in Shenzhen for at least 6 months in the past 12 months from each household.

In 2018, in 10 administrative districts, 1 community from each was randomly selected. A total of 100 households from each community were selected using the proportional probability sampling method. A Kish grid was adopted to recruit one resident aged 18–69 years who lived in Shenzhen for at least 6 months in the past 12 months from each household.

Data collection

All participants completed a study-specific questionnaire that collected demographic and lifestyle information about their sex, age, educational level, marital status, smoking behaviour, alcohol use and physical activity via face-to-face interviews administered by trained healthcare workers.

The physical examination followed a standard protocol. Body mass index (BMI) was calculated by dividing weight (kg) by the square of height (m2), and obesity was defined as a BMI of 28.0 kg/m2 or above. Participants who have smoked at least one cigarette per day in the past 6 months or currently smoking cigarettes were defined as current smokers; former smokers were defined as participants who have smoked at least one cigarette each day in the past 6 months and quit smoking for at least 1 month; and never smokers were participants who have never smoked or smoked <1 cigarette per month. Participants who drank at least once a week in the past 6 months and currently consuming alcohol were defined as current drinkers; former drinkers as participants who drank regularly in the past 6 months but quit for at least 1 month, and never drinkers as participants who have never drank or drank <once a month. Those who participated in physical activity at least three times per week, at least 10 min each time, were defined as doing regular physical activity, otherwise as having sedentary behaviour. Participants were considered as having diabetes mellitus if their fasting plasma glucose was 7.0 mmol/L and above.13

Participants were instructed not to smoke, exercise, or consume coffee, alcohol, or tea for at least 30 min prior to the examination. BP was measured by trained physicians using a mercury sphygmomanometer with appropriately sized arm cuffs after the participants had rested for 5 min while seated. The monitors were calibrated and tested by the sphygmomanometer provider and received approval from the State Bureau of Quality and Technical Supervision, following standard protocols. Measurements were taken three times successively, with a 1 min interval between each. The mean SBP and mean DBP were calculated by averaging these three BP measurements. Quality control for the monitors and result recording was conducted daily by designated staff, adhering to a standard survey protocol.

Hypertension was defined as SBP ≥140 mm Hg or DBP ≥90 mm Hg,4 14 or has ever taken antihypertensive medication.

Awareness of hypertension was calculated as the percentage of patients with hypertension responding affirmatively to the question, ‘Have you ever been told/diagnosed to have hypertension?’.15

Treatment of hypertension was calculated as the percentage of participants responding ‘yes’ to the question, ‘Have you taken prescribed medicine for hypertension within 2 weeks?’.

Control of hypertension was calculated as the percentage of participants with hypertension with SBP of less than 140 mm Hg and DBP of less than 90 mm Hg.

Patient and public involvement

No patients were involved.

Statistical analysis

Descriptive analysis was used to summarise participants’ characteristics by sex for each study period. Continuous variables were presented as mean (SD) and categorical variables were presented as frequency (percentage). Selected percentiles of sex-specified mean SBP and DBP are presented to gain a more comprehensive understanding of overall and percentile-specific trends of BP. Between-group differences were tested using a t-test or one-way analysis of variance (depending on the availability of study period data), and a Χ2 test. Changes in SBP and DBP were determined in comparison with the data in 1997; prevalence, awareness, treatment and control of hypertension were determined based on the data in 2009. Restricted maximum likelihood regressions were used to characterise temporal linear trends. The weights were calculated with adjustment to the standard population, the Chinese Census 2010. Additional sensitivity analysis of the prevalence of the lower threshold for diagnosing hypertension (SBP ≥130 mm Hg or DBP ≥80 mm Hg) according to the 2022 China Hypertension Clinical Practice Guideline Prospectus and American College of Cardiology/American Heart Association (ACC/AHA) hypertension guidelines5 16 was also estimated. SAS analytical software V. 9.4 (SAS Institute) was used for statistical analyses, and a two-tailed p<0.05 was considered statistically significant.

Results

Characteristics of study participants

A total of 26 621 people were surveyed: 8266 people in 1997, 8599 people in 2009 and 9756 people in 2018. Among these people, 38% in 1997, 43% in 2009 and 43% in 2018 were males. The participant characteristics by sex and survey year are shown in table 1.

Table 1

Characteristics of the study population

Mean SBP and DBP and prevalence of hypertension

The age-adjusted mean SBP among males increased from 117 mm Hg (SD=16) to 123 mm Hg (SD=15), from 1997 to 2018 (p<0.001). The age-adjusted mean DBP among males was 75 mm Hg (SD=11) in 1997 and increased to 79 mm Hg (SD=11) in 2018 (p<0.001). The age-adjusted mean SBP and DBP among females followed a similar increasing trend from 1997 to 2018 (table 2). The distribution of mean SBP and DBP in selected percentiles is presented in figure 1. All percentiles of mean SBP <140 mm Hg showed an increasing trend in males. There was an upward but non-parallel trend of mean DBP among males in all percentiles. In females, the highest percentile of mean SBP >140 mm Hg exhibited a notable decreasing trend, whereas slight upward trends were observed in other percentiles of both SBP and DBP. The age-adjusted prevalence of hypertension among males rose rapidly from 17.71% (95% CI: 16.60% to 18.90%) in 2009 to 24.01% (95% CI: 22.84% to 25.22%) in 2018 (p<0.001), whereas the prevalence among females remained stable at around 13.5% (p=0.98) (table 3).

Table 2

Age-standardised blood pressure

Figure 1

Selected percentiles for mean SBP and DBP among adults in Shenzhen from 1997 to 2018. DBP, diastolic blood pressure; SBP, systolic blood pressure.

Table 3

Age-standardised prevalence, awareness, treatment and control of hypertension

Awareness, treatment and control of hypertension

The age-adjusted rate for awareness of hypertension among males and females decreased from 58.85% (95% CI: 55.19% to 62.30%) to 52.29% (95% CI: 49.38% to 51.11%) (p=0.004), and 66.66% (95% CI: 62.70% to 70.52%) to 57.48% (95% CI: 53.60% to 61.25%) (p<0.001) from 2009 to 2018, respectively (table 3). The awareness rate differed across age groups, with higher awareness observed among people aged over 40 years, and the awareness rate remained low among adults aged 18–39 years from 2009 to 2018. The rates of treatment among those who were aware of their hypertension were 79.60% (95% CI: 76.18% to 82.63%) and 84.56% (95% CI: 80.39% to 87.91%) in 2018. There was an 8% decrease (p=0.001) among males and an 11% decrease (p<0.001) among females in the overall treatment rate of hypertension from 2009 to 2018. The control rate among those who were treated increased from 39.51% (95% CI: 34.69% to 44.79%) to 51.09% (95% CI: 46.62% to 55.56%) among males from 2009 to 2018, and the rate remained stable among females around 45%. On the other hand, no significant changes regarding the age-adjusted control rate among all the people with hypertension were observed in the last decade.

Prevalence of hypertension according to the 2022 China Hypertension Clinical Practice Guideline Prospectus

Using the lower cut-off values for hypertension (SBP ≥130 mm Hg/DBP ≥80 mm Hg), the age-adjusted prevalence of hypertension was 42.70% (95% CI: 42.21% to 45.20%) for males and 28.12% (95% CI: 26.78% to 29.49%) for females in 2009. The prevalence increased to 50.49% (95% CI: 49.09% to 51.89%) in 2018 for males, while no significant changes of the prevalence of hypertension by lower cut-off values in females were reported (table 4).

Table 4

Age-standardised prevalence of hypertension according to the 2022 China Hypertension Clinical Practice Guideline Prospectus

Discussion

From 1997 to 2018, age-adjusted mean SBP increased by 5.6 mm Hg in males, and by 2.0 mm Hg in females. Age-adjusted mean DBP displayed a similar pattern, with an increment of 4.0 mm Hg in males and 1.9 mm Hg in females. An increasing prevalence of hypertension was witnessed from 17.71% to 24.01% among males, but remained stable at around 13.5% among females. Awareness and treatment rates of hypertension have been found remaining poor compared with high-income settings, and significant decrease in both sexes over the last decade was also reported. Therefore, effective prevention, management and control of hypertension should be continuously advocated, and more attention should be paid to improving health literacy among high-risk individuals and patients with hypertension.

The global age-standardised prevalence of hypertension was 32% in females and 34% in males in 2019, based on the definition of SBP over 140 mm Hg and DBP over 90 mm Hg, which were much higher compared with the findings in our study. Since 1990, the prevalence of hypertension has doubled globally until 2019, with the greatest increase occurring in low-income and middle-income countries (LMICs).17 The trends identified in LMICs,18 with approximately a 7.7% increase of hypertension prevalence during 2000–2010, were reported, which was more pronounced in men with a 10–15% increase between 1990 and 2019.17 In our study, a 6.3% increase of hypertension prevalence among males was reported, but the prevalence of hypertension in females remained stable in the last decade. This trend may be attributed to the increasing rates of control among those treated, rising from 43.96% to 47.85%. Hypertension risk factors among study population were found to be more prevalent by time and could also contribute to the increasing trend of hypertension. Moreover, an overall lower BP was observed in females, despite a significant increase in BP and a decline in treatment rates.

From the national report, prevalence of hypertension among males has been increasing in the last 10 years, which was in line with our findings, but decreasing steadily among females.15 The treatment rate was 47% in females and 38% in males in LMICs, slightly lower than the rates reported in our study.17 In high-income countries, the prevalence has decreased, and the treatment rate of hypertension reached 80% with control rates of up to 60%. A population-based study in the USA showed a decrease in age-standardised prevalence of hypertension from 48.4% to 45.4% from 1999 to 2016, with an improved proportion of control among treated hypertension from 25.6% to 43.5%.19 Though we found an improvement in the proportion of controlled hypertension with treated patients, the treatment rate of hypertension remains low, and even decreased in our study over the recent decade. Our findings on the prevalence of hypertension based on the new definition of hypertension (higher than 130 mm Hg in SBP or 80 mm Hg in DBP) were similar to the USA (49.6% by 2018), while the prevalence in females was much lower compared with the USA (28.7% vs 51.6%).20 Moreover, under the new definition of hypertension, a 6.8% increase of the prevalence of hypertension in males was found from 2009 to 2018, but no significant changes were found in females. Attention to pre-hypertension, especially in males, is urgently called in China as a public health consideration. Additional studies are needed to explore the disparities in the prevalence of hypertension across different population subgroups.

Applications of the most recent 2022 China Hypertension Clinical Practice Guideline Prospectus (SBP ≥130 mm Hg or DBP ≥80 mm Hg) will result in a substantial increase of patients with hypertension in both sexes, and especially in the young and middle-aged groups.5 The proposed guideline is similar to the 2017 ACC/AHA hypertension guidelines,21 using a lower threshold of hypertension diagnosis criteria, which may lead to earlier detection and treatment, and might be cost-effective in the long term. However, heavier workloads and burdens due to a greater number of patients may lead to increased stress level in health workers in primary healthcare settings, which may counterintuitively reduce the efficiency of the implementation of BP management.22

The age-standardised awareness and treatment rates of hypertension decreased in both sexes from 2009 to 2018. It is noteworthy that in 2009, China embarked on a major healthcare reform for equal access to primary care, which aimed to establish national primary and critical public health services to promote health for all citizens in 2009.23 In response to the changes in national policy, the awareness, control and treatment rates were promoted in the hypertension management assessment, and the Chinese Hypertension League launched a guideline focusing on community management in the same year.3 These policies, guidelines of management and relevant financial investment potentially improved screening, early diagnosis and treatment of hypertension in the community, with extended coverage of health insurance schemes and increased availability of healthcare services. However, our observation of reduction in awareness and treatment rates indicated the challenges remain. The low utilisation and inadequate primary healthcare services would be one of the key barriers to further improve the quality of care.24–26 From 2010 to 2017, there was only a 4.4% increase in the number of doctors in township health centres who had formal medical education.24 25 On the other hand, lack of incentive and opportunity for promotion also introduces fatigue among primary healthcare providers to sustain the quality of care for a population with hypertension.

The average BP among males was found to be higher compared with females from 1997 to 2018. This revealed gender disparities in the medication adherence and treatment details for BP management. Females were about two times more likely to receive antihypertensive treatment than males and had different drug use patterns.27 Although no sex difference regarding antihypertensive medication adherence was reported in a meta-analysis of 82 studies,28 factors associated with lower antihypertensive medication adherence should be noted. Lifestyle modifications were found to be one of the most important factors associated with higher antihypertensive medication adherence in both sexes.29 In the present study, males were more likely to have self-reported unfavourable lifestyles and no significant lifestyle behaviour improvement over the two decades. Other factors associated with lower antihypertensive medication adherence such as polypharmacy, high cost of antihypertensive medication and overweight were also found to be more clustered among males.

Implications

Elevated BP as a major risk factor for CVDs represents a large public concern around the world.30 31 There was an increasing trend in both SBP and DBP among Shenzhen adults between 1997 and 2018. To better manage the burden associated with hypertension on a population level, both the contents and implementation of the China Essential Public Health Service should be revised. Therapeutic inertia and burnout as a result of the assessment system of the China Essential Public Health Service may be relieved via the improvement. Decreases in awareness and treatment rates among individuals with hypertension were observed from 2009 to 2018. Though the comprehensive health system reform over the past decades has strengthened primary healthcare services, challenges remain in maintaining the quality of care. Even though these rates were higher compared with other regions in China, they still remained universally low. The new cut-off point for hypertension definition has doubled the prevalence; while this may be beneficial of timely diagnosis and early treatment initiation, it may also require commensurate capacity at primary healthcare centres to maintain the quality of care. Pre-hypertension became more prevalent in the last decade, which needed more attention. Health education and promotion are advocated to improve the health literacy of the general population, and strategies should be initiated to further improve hypertension detection, treatment and control.

While our study provided valuable insights into hypertension trends in Shenzhen, China, several limitations should be acknowledged: (1) this is a cross-sectional study; hence, no causal or temporal inferences between potential risk factors and hypertension can be determined; (2) out-of-office BP is not available, so hypertension was defined by office BP and self-reported medical history, which may result in recall bias and reporting bias; (3) no information on antihypertensive medication usage was available from the 1997 survey; (4) the number of replacements in participant recruitment was not available; and (5) the study population were all recruited from Shenzhen, which is a city of immigration with a rapid turnover of residents; thus, representativeness and generalisability were of concern. Future studies are warranted to investigate potential factors related to changes in the prevalence of hypertension.

Conclusions

In conclusion, we observed an increased age-adjusted SBP and DBP from 1997 to 2018 in females and males, and the prevalence of hypertension increased from 2009 to 2018 among males, in Shenzhen, China. Meanwhile, the awareness, treatment and control of hypertension did not improve between 2009 and 2018. Further investigations are needed to explore the underlying reasons for the change in trends to improve BP management in Shenzhen city. Health education and promotion are advocated to be conducted to improve the health literacy of the general population, and strategies should be initiated to further improve hypertension detection, treatment and control.

Data availability statement

Data are available upon reasonable request.

Ethics statements

Patient consent for publication

Ethics approval

This study involves human participants and ethics approval was obtained from the Ethics Committee of the Shenzhen Center for Chronic Disease Control (no: SZCCC-2018-019-02-PJ). All participants gave informed consent to participate in the study.

Acknowledgments

We appreciate the contributions made by the community healthcare centres including operations and particularly data collection. We also thank the participants for their involvement.

References

Footnotes

  • KP, WC and XL contributed equally.

  • Contributors Guarantor—LL. Conceptualisation—KP and LL. Methodology—KP, WC, XL, YL and MO. Software and analysis—WC and YL. Validation—YL, MO and XL. Formal analysis—WC and YL. Resources—LL. Writing (original draft preparation)—MO, XL, YL, WC, JG, LS and KP. Writing (review and editing)—ZW, YW, JH, WW, HZ, KL, GH, YS, YhX and YxX. Visualisation—XL. Project administration—LL and KP. All authors have read and agreed to the published version of the manuscript.

  • Funding This study was funded by the Sanming Project of Medicine in Shenzhen (no. SZSM201911015), Shenzhen Medical Key Discipline Construction Fund (no. SZXK065), the Basic and Applied Basic Research Foundation of Guangdong Province (no. 2021A1515110307) and the Young Talent Program of the Academician Fund, Fuwai Hospital Chinese Academy of Medical Sciences, Shenzhen (no. YS-2020-006).

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

  • Provenance and peer review Not commissioned; externally peer reviewed.