Prevalence of hypertension among type 2 diabetes mellitus patients in China: a systematic review and meta-analysis

Abstract

This study aimed to estimate the prevalence of hypertension in Chinese patients with type 2 diabetes mellitus (T2DM) using the results of a regional study. The studies were reviewed using PubMed, EMBASE, Web of Science, the Cochrane Library, China National Knowledge Infrastructure, China Biology Medicine, Wan Fang Data and Chinese Science Citation Database. After screening articles and data extraction, Stata V.16 was used for statistical analysis. This study was registered in the Prospective Register Systematic Reviews (CRD42020170649). A total of 2126 articles were identified, and nine papers were finally included. Random-effects modelling showed that the pooled prevalence of hypertension among Chinese patients with T2DM was 54% (95% CI 47 to 61%). Subgroup analysis showed that the prevalence in men (59.8%; 95% CI 49.0 to 70.7%) was higher than that in women (40.2%; 95% CI 29.3 to 59.2%). The prevalence in North China was higher than that in East China. The prevalence in institution-based settings (56%; 95% CI 48 to 64%) was higher than that in community-based settings (51%; 95% CI 34 to 69%). Appropriate preventive measures should be undertaken, such as health education, to control and reduce the risk of hypertension in diabetic patients and reduce the burden of cardiovascular disease.

Introduction

According to the International Diabetes Federation, diabetes affects one in 10 adults aged 20–79 y worldwide, a total of 537 million people; among them, type 2 diabetes mellitus (T2DM) accounts for the vast majority (>90%).¹ Over the past 40 y, with the ageing population and continuous changes in living environment and lifestyle, the prevalence of diabetes in China has increased rapidly from 0.67% in 1980 to 10.4% in 2013.² According to 2015 survey data, there were approximately 109.6 million adults aged 20–79 y with diabetes.³

Diabetes mellitus is one of the most common endocrine and metabolic diseases. Patients with diabetes mellitus often have other important risk factors for cardiovascular and cerebrovascular diseases, such as hypertension and dyslipidaemia. Some studies have noted that the prevalence of diabetes combined with hypertension has a significant upwards trend with age.⁴ Epidemiological data show that the incidence of hypertension in patients with T2DM is 2.0–2.5 times that in patients without T2DM, and the peak incidence of hypertension in patients with T2DM is 10 y earlier than that in the normal population.⁵ In addition, compared with T2DM patients without hypertension, T2DM patients with hypertension have increased blood pressure fluctuations and are more likely to experience myocardial infarction, cerebrovascular accidents (such as stroke, cerebral thrombosis, etc.) and peripheral large vessel (arterial/venous) disease, and T2DM might aggravate capillary (such as retinal) lesions/renal failure in the late stage, significantly increasing mortality.⁶ It can be concluded that T2DM with hypertension is one of the main risk factors for the occurrence of cardiovascular and cerebrovascular diseases and one of the main risk factors for other cardiovascular diseases and death that can be controlled.

To date, no meta-analysis was found on the prevalence of hypertension in Chinese patients with T2DM. It is important to determine the prevalence of hypertension in Chinese diabetic patients for the prevention and treatment of cardiovascular and cerebrovascular diseases. Therefore, this study aimed to use the results obtained from these regional studies to estimate the prevalence of hypertension in patients with T2DM on a national scale, which was conducive to strengthening the management of comorbidity and improving the overall quality of medical services.

Materials and Methods

Study protocol and systematic review registration

This meta-analysis and systematic review was conducted to identify the pooled prevalence of hypertension among DM patients in China. The review was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (Supplementary File 1). This study is registered in the Prospective Register Systematic Reviews (PROSPERO) database (CRD42022370381).

Study design and setting

A systematic review and meta-analysis that included all articles and that reported the prevalence of hypertension among T2DM patients in China was conducted. All the included articles were cross-sectional studies.

Search strategy and data source

The following databases were searched from inception to December 2022: PubMed, EMBASE, Web of Science, the Cochrane Library, China National Knowledge Infrastructure, China Biology Medicine, Wan Fang Data and Chinese Science Citation Database.

The search was performed using keywords and Boolean operators (AND and OR) either individually or in combination using the following keywords: hypertension, blood pressure, China, prevalence and diabetic mellitus (Supplementary File 2).

Data extraction and data management

Two reviewers (XLY and LNX) independently extracted information using an advance-designed standardised data extraction form. After collecting the results, the titles were independently reviewed and abstracts of all citations were obtained. Titles or abstracts eligible for full text download were read to further consider whether they should be included in the study. Authors were contacted for additional details as necessary. Multiple surveys conducted at different time points appearing in an article were considered separate studies. The full-text search results found nine qualifying studies. Then two reviewers double checked the retrieved articles to ensure that there were no mistakes. Disagreements were resolved through team discussion or consulting a third reviewer (QTY).

All the retrieved studies were imported into EndNote X9 software (version X9.1; Clarivate Analytics Inc., Philadelphia, PA, USA), and duplicate studies were deleted.

Criteria for considering studies for the review

The inclusion criteria were published observational studies from inception to 21 December 2022, with T2DM patients; only peer-reviewed and published articles written in any language; and institutional and community-based studies with the prevalence of hypertension as the outcome. The exclusion criteria were studies that did not disclose the prevalence of hypertension among T2DM patients, experimental studies, reviews, commentaries and case series/reports.

Quality assessment and risk of bias in individual studies

The methodological consistency of the included studies was evaluated using the risk of bias assessment tool in prevalence studies proposed by Hoy et al.⁷ This tool is designed to assess the quality of meta-analyses of non-randomised studies. It is easy to use and has high interrater agreement. The tool contains 11 items: items 1–4 assess the external validity, items 5–10 assess the internal validity and item 11 is a summary of the reviewer's overall risk assessment based on the responses of the above 10 items, scored 0 if yes and 1 if no. Studies were rated as having a low risk (<3), moderate risk (4–6) or high risk (7–9) of bias.

In addition, adequate sampling methods, consistent methods and procedures for collecting data and the representative sample size were considered indicators of the quality of the study. Studies of high quality were studies that revealed all of the points mentioned above (Supplementary File 3).

Data analysis and presentation of results

The characteristics of the included studies (first author, year of publication, year of survey, study area/region, study design, sample size, number of cases, prevalence of hypertension in diabetic patients) were extracted and summarised in Microsoft Excel 2019 software (Microsoft, Redmond, WA, USA). Extracted quantitative data were exported to Stata V.16 (Stata Corp., College Station, TX, USA) for analysis.

Rates and their standard errors were calculated for each original study from the data collected. Meta-regression was weighted by number of subjects unless otherwise specified. Forest plots were drawn to represent the overall prevalence of hypertension among patients with T2DM and the degree of statistical heterogeneity between studies. The heterogeneity between studies was analysed by the χ² test and p values, and the size of heterogeneity was evaluated by I². A fixed effect model was used when p>0.1, and I²≤50% indicated that there was no statistical heterogeneity among articles. If p≤0.1 and I²>50%, the cause of heterogeneity was analysed. If the cause of heterogeneity was not analysed, a random effects model was used. When the heterogeneity was too large (I²≥75%), subgroup analysis, sensitivity analysis or only descriptive analysis was performed. To assess possible publication bias, the funnel plot test method was used.

Outcomes and prioritisation

The primary outcome was the prevalence of hypertension among T2DM patients in China.

Data synthesis

The original articles were represented using a forest plot and table. Because there was heterogeneity among the studies, a random effects model was used to determine the pooled prevalence of hypertension in China. The geographical regions of the study, gender of the researcher and source of data collection were summarised by a subgroup analysis. Heterogeneity was investigated using Cochrane's Q, and I² statistics were quantified. The results with corresponding 95% CIs are presented.

Results

Screening flow

According to the search strategy set in advance, a total of 2126 articles were retrieved in the target database. EndNote X9 software was used to remove 32 duplicate articles, and 2002 articles that did not meet the inclusion criteria were excluded from the remaining 2094 articles by reading the titles and abstracts. Eighty-three articles were excluded from the remaining 92 articles by intensive reading of the full texts, and nine eligible articles were finally determined for inclusion in the analysis. See Figure 1 for specific article screening steps.

Figure 1.

Flowchart of a systematic review and meta-analysis for the prevalence of hypertension among T2DM patients in China.

Study characteristics

This systematic review and meta-analysis included a total of nine studies. Six of the studies were conducted in southern Chinese cities, two of the studies were from northern Chinese cities and one of the studies was a national study. In addition, data of six studies were from medical institutions, and data from three studies were from community residents. The studies were all institutional-based, cross-sectional studies (Table 1).

Table 1.

Characteristics of studies included in the systematic review and meta-analysis of the prevalence of hypertension among T2DM patients in China

					Sample size		Cases
Authors	Publication year	Study design	Study area/region	Study setting	Male	Female	Male	Female	Prevalence (%)
Zou8	2002.05	Cross-sectional	Guangdong/South China	Institution based	101	79	43	37	44.40%
Jiang et al.9	2020.03	Cross-sectional	Guiyang/Southwest China	Community based	2139		1047		48.95%
Zou et al.10	2002.05	Cross-sectional	Nanchang/East China	Institution based	173	132	119	85	66.89%
Yang11	2019.06	Cross-sectional	Ningbo/East China	Institution based	1685	1330	968	801	58.67%
Zhong and Xiong12	2014.01	Cross-sectional	Wuhan/Central China	Institution based	472	88	400		71.43%
Qiu et al.13	2011.04	Cross-sectional	Nationwide	Institution based	398	373	373		48.38%
Song14	2019.04	Cross-sectional	Bengbu/East China	Community based	361		113		31.30%
He15	2011.05	Cross-sectional	Taiyuan/North China	Community based	50	39	67		75.28%
Xia16	2015.03.	Cross-sectional	Shanxi/North China	Institution based	56	42	42		42.86%

The pooled prevalence of hypertension

In the analysis of nine studies according to the random effects model, the results showed that the pooled prevalence of hypertension among T2DM patients in China was 54% (95% CI 47 to 61%). In this study, the heterogeneity was tested, and I²=97.1% and p<0.001 indicated the presence of heterogeneity (Figure 2).

Figure 2.

Forest plot of the nine studies that assessed the pooled prevalence of hypertension among T2DM patients in China.

Funnel test and Egger's test

The funnel plot was basically symmetrical, indicating that there was no publication bias. However, each study was outside the 95% confidence limit of this plot, suggesting large heterogeneity, and further subgroup analysis was needed (Figure 3).

Figure 3.

Funnel plots showed basic symmetry, indicating that there was no publication bias among the studies. Note: Standard normal deviate (SND) is defined as the sample mean divided by its standard error. Precision is defined as the inverse of the standard error. Regression analysis of precision with SND. The resulting regression equation is SND=a+b×precision. If there is asymmetry, the effect of a small sample test will systematically deviate from that of a large sample test, and the regression line will not pass through the starting point. In addition, p=0.922, which is >0.05, so there was no publication bias. When the x-axis (precision) value is 0, the corresponding y-axis is SND (sample mean divided by its standard error), and the 95% CI can be obtained by calculating the sample mean and standard error.

In addition, Egger's test was used to assess publication bias. The results showed that p=0.922 was >0.05, suggesting that there was no publication bias (Figure 4).

Figure 4.

Egger's test indicated that there was no publication bias among the studies.

Subgroup analysis

The pooled prevalence of hypertension among patients with T2DM in East China and North China was 52% (95% CI 35 to 69%) and 59% (95% CI 27 to 91%), respectively (Figure 5).

Figure 5.

Forest plot for the subgroup analysis by region of the country. Note: The software specified that p values were not shown when there were fewer than three study samples.

The pooled prevalence of hypertension among patients with T2DM among institution-based and community-based studies was 56% (95% CI 48 to 64%) and 51% (95% CI 34 to 69%), respectively (Figure 6).

Figure 6.

Forest plot for the subgroup analysis by study setting.

The combined prevalence of hypertension was higher in men (59.8%; 95% CI 49.0 to 70.7%) with T2DM than in women (40.2%; 95% CI 29.3 to 59.2%) (Table 2 and Figure 7).

Table 2.

Subgroup analysis by gender of the primary study participants

Gender	Studies included, n	Prevalence (95% CI)	Heterogeneity statistics	I 2 (%)	p	τ 2
Male	7	59.8 (49.0 to 70.7)	293.71	98%	<0.001	0.02
Female	7	40.2 (29.3 to 59.2)	293.71	98%	<0.001	0.02

Note: Tau-squared (τ²): the variance of the true effect sizes, which is also one of the indicators to judge the heterogeneity. Combining the 95% CIs for each parameter, larger τ² indicates greater heterogeneity.

Figure 7.

Forest plot for the subgroup analysis by gender of primary study participants.

Discussion

This systematic review and meta-analysis based on nine Chinese studies summarised the prevalence of hypertension in patients with T2DM in China. The results showed that the prevalence of hypertension in Chinese patients with T2DM was 54%. According to The Chronic Disease and Risk Factor Surveillance in China (CCDRFS) study, the detection rate of high-normal blood pressure in Chinese adults aged ≥18 y was 50.9% in 2018.¹⁷ This means that people with a chronic disease such as diabetes have a greater risk of becoming hypertensive compared with people without diabetes.

According to the articles included in this study, the prevalence of hypertension in patients with T2DM in North China was higher than that in East China. This finding is basically consistent with the reports of Wang et al. and Chen et al. on the incidence of hypertension and regional differences.^18,19 As is well known, urban living, lack of physical activity, genetic factors and a large intake of animal protein may increase the risk of diabetes or hypertension, while the high content of salt, fat, carbon and water in the diet in northern China, as well as the cold season and less physical activity, may increase the risk of illness. ^20,21 The study also showed that the prevalence of hypertension in men with T2DM was higher than that in women, similar to data from a WHO survey.²² Differences in results may be due to differences in diagnostic criteria, detection methods, study years, diabetes management and related socioeconomic factors of study participants between the two regions. This study showed a high prevalence of hypertension among Chinese patients with T2DM. The high risk of diabetes combined with hypertension could lead to serious consequences, such as cardiovascular and cerebrovascular complications. It is essential to fully understand the prevalence of hypertension in Chinese patients with T2DM and implement effective interventions such as health education, diet management, medication guidance and exercise rehabilitation programmes to reduce the national morbidity and mortality due to diabetes or hypertension and its related complications.^23,24

In conclusion, this study estimated the prevalence of hypertension in Chinese patients with T2DM and conducted subgroup analyses by gender and region. It is conducive to understand the prevalence of hypertension in patients with T2DM in China, and provide reference for early clinical diagnosis, early prevention and treatment.

Strengths and limitations

To the best of our knowledge, this study is the first systematic review to investigate the prevalence of hypertension in Chinese patients with T2DM, and multiple databases were used to search for articles.

A limitation of this study is that it used a random effects model to accommodate variability, but the heterogeneity remains high, and caution is also needed to interpret the data. The small number of articles included in this study prevented further analysis according to study time. In addition, this meta-analysis should be further studied in depth to evaluate the combined factors leading to hypertension.

Conclusions

To reduce the incidence of diabetes combined with coronary heart disease, stroke and other cardiovascular and cerebrovascular diseases, we should first comprehensively control patients with elevated blood pressure. Condition-based approaches and country-specific appropriate preventive measures should be implemented to reduce the burden of hypertension in people with diabetes and to improve the overall quality of healthcare services. Management of comorbidities, early screening, early diagnosis and early treatment should be emphasised. In addition, identifying predisposing factors for the development of hypertension in diabetic patients still requires further investigation.

Authors’ contributions

XZ and XLY contributed equally to the work as first authors. XZ contributed to designing the study; collecting, entering, analysing and interpreting the data; and preparing the manuscript. XLY and LNX were involved in the study design, study selection, data extraction, statistical analysis and drafting of the manuscript. SL, YSY and QTY were involved in interpreting the data, data extraction and statistical analysis. All authors read and approved the final manuscript.

Funding

None.

Competing interests

None declared.

Ethical approval

Not required.

Data availability

All raw data generated or analysed during the current study are available from the corresponding author upon reasonable request.