- Data source
We used data from the 2011 China Health and Nutrition Survey (CHNS), which is an ongoing, large-scale, population-based survey initiated in 1989. CHNS used a stratified multistage, random cluster sampling strategy to select participants from 288 communities across a large number of primary provinces/autonomous cities (13). The CHNS 2011 was conducted across more than 10 provinces and autonomous cities, including Beijing, Chongqing, Guangxi, Guizhou, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Liaoning, Shaanxi, Shandong, Shanghai, Yunnan, and Zhejiang. Our sample from the CHNS 2011 includes 5,884 households and 12,991 adults, which provides a large nationwide sample of the Chinese population in terms of major behavioral health and disease burden.
We restricted our analysis to those aged ≥ 18 years (n = 12,991) and focused on those with hypertension (n = 3,645) in 2011. Excluding missing values, 3,579 adults were included in the final dataset for analysis. Written informed consent was obtained from each participant before any data were collected. Note that more recent CHNS data have not yet been released for us.
- Measurement and definitions
We selected variables regarding knowledge about and medical history of hypertension, as well as demographics, socioeconomic status, and lifestyle behaviors from the adult household questionnaire in CHNS. We categorized geographic regions into three groups: Western China (Guangxi, Guizhou, and Chongqing), Eastern China (Shanghai, Beijing, Jiangsu, Liaoning, and Shandong) and Central China (Henan, Hubei, and Heilongjiang). Marital status was classified into currently married and single (i.e., never married, divorced, widowed, or separated). There were six a priori characteristics selected: residency (urban vs. rural), ethnicity (Han vs. minority), occupation (employed vs. unemployed), educational attainment [elementary school (≤6 years of education), middle school (6-9 years of education), high school or technical school (9-12 years of education), and college or above (>12 years of education]. Smoking status was defined as non-smoker (subjects who responded negatively to “have you ever smoked cigarettes?”), ex-smoker (subjects who responded positively to questions “have you ever smoked cigarettes?” , but negatively to “do you still smokes cigarettes?”;, and current smoker(as subjects who responded both positive answers to questions “have you ever smoked cigarettes?” and “do you still smokes cigarettes?”). Alcohol consumption status was defined as drinker (subjects replied “yes” to “do you regularly drink alcohol since last year?” and non-drinker. Medical insurance status was classified as insured vs. not insured. The physical examination, including height and weight, were measured by health care professionals. Weight was measured in light closing to the nearest 0.1kg on a calibrated beam balance, while height was measured to the nearest 0.1cm using a portable stadiometer. Body mass index (BMI) was calculated as weight (kg) divided by the height squared (m2). Overweight and obesity were defined as a BMI of at least 24kg/m2 and 28kg/m2, respectively, based on the recommendations of the Working Group on Obesity in China.(14)
- Assessment of hypertension and hypertension awareness, treatment, and control
The measurement and definition of hypertension was reported according to the 7th Chinese Joint National Commission guidelines.(15) A standard mercury sphygmomanometer was used by well-trained physicians to measure SBP and DBP on the right arm in triplicate after a 10-minute seated rest. The mean of the three readings was calculated and used in all analysis. Hypertension was defined as having an average SBP ≥ 140 mm Hg and/or an average DBP ≥ 90 mm Hg, and/or a self-reported previous diagnosis of hypertension by a health care provider, and/or taking antihypertensive drugs currently. Awareness of hypertension status was defined as a self-report of any previous diagnosis of hypertension by a health care provider. Treatment of hypertension was defined as a self-reported use of antihypertensive medications at present. Control of hypertension was defined as having an average SBP < 140 mmHg and an average DBP < 90 mmHg while under pharmacological treatment for hypertension.
We compared our results on hypertension prevalence, awareness, treatment, and control rates with results from China Health and Nutrition Survey 2001 (CHNS 2001) and the International Collaborative Study of Cardiovascular Disease in ASIA (InterASIA 2000-2001). Detailed information on these two studies have been reported previously. (16, 17). In brief, CHNS 2001 study was conducted in 31 provinces, autonomous regions and municipalities throughout China. Stratified multistage cluster sampling was used to recruit participants and 141,892 participants ≥18 were analyzed as the final sample size. In the InterASIA study, stratified sampling method was used to select a nationally representative sample of population aged 35-74 years in China during 2000-2001, and 14,989 subjects were included in the analysis. These comparisons can provide evidence on the improvements in hypertension prevalence, awareness, treatment and control over the past ten years and between different samples.
- Statistical analysis
Data were presented as mean SD for continuous and percentages for categorical variables according to gender, respectively. Differences between groups were tested using two-sample student t-tests for continuous variables and the Chi-square test for categorical variables. Multivariable logistic regression models were fit to explore the associations between relevant risk factors and hypertension awareness and treatment.
We also investigated the adjusted associations between independent variables and taking antihypertensive drugs among subjects who were aware of hypertension. Finally, characteristics and proportions of subjects by age groups were analyzed to identify the subpopulations that were more likely to take antihypertensive medications (“adherence”) in the subsample of participants who took treatments for hypertension. All the analysis was done using Stata 15.0 (StataCorp., 2017). P values were 2-tailed and p < 0.05 was considered to be statistically significant.
- Data source
We used data from the 2011 China Health and Nutrition Survey (CHNS), which is an ongoing, large-scale, population-based survey initiated in 1989. CHNS used a stratified multistage, random cluster sampling strategy to select participants from 288 communities across a large number of primary provinces/autonomous cities (13). The CHNS 2011 was conducted across more than 10 provinces and autonomous cities, including Beijing, Chongqing, Guangxi, Guizhou, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Liaoning, Shaanxi, Shandong, Shanghai, Yunnan, and Zhejiang. Our sample from the CHNS 2011 includes 5,884 households and 12,991 adults, which provides a large nationwide sample of the Chinese population in terms of major behavioral health and disease burden.
We restricted our analysis to those aged ≥ 18 years (n = 12,991) and focused on those with hypertension (n = 3,645) in 2011. Excluding missing values, 3,579 adults were included in the final dataset for analysis. Written informed consent was obtained from each participant before any data were collected. Note that more recent CHNS data have not yet been released for us.
- Measurement and definitions
We selected variables regarding knowledge about and medical history of hypertension, as well as demographics, socioeconomic status, and lifestyle behaviors from the adult household questionnaire in CHNS. We categorized geographic regions into three groups: Western China (Guangxi, Guizhou, and Chongqing), Eastern China (Shanghai, Beijing, Jiangsu, Liaoning, and Shandong) and Central China (Henan, Hubei, and Heilongjiang). Marital status was classified into currently married and single (i.e., never married, divorced, widowed, or separated). There were six a priori characteristics selected: residency (urban vs. rural), ethnicity (Han vs. minority), occupation (employed vs. unemployed), educational attainment [elementary school (≤6 years of education), middle school (6-9 years of education), high school or technical school (9-12 years of education), and college or above (>12 years of education]. Smoking status was defined as non-smoker (subjects who responded negatively to “have you ever smoked cigarettes?”), ex-smoker (subjects who responded positively to questions “have you ever smoked cigarettes?” , but negatively to “do you still smokes cigarettes?”;, and current smoker(as subjects who responded both positive answers to questions “have you ever smoked cigarettes?” and “do you still smokes cigarettes?”). Alcohol consumption status was defined as drinker (subjects replied “yes” to “do you regularly drink alcohol since last year?” and non-drinker. Medical insurance status was classified as insured vs. not insured. The physical examination, including height and weight, were measured by health care professionals. Weight was measured in light closing to the nearest 0.1kg on a calibrated beam balance, while height was measured to the nearest 0.1cm using a portable stadiometer. Body mass index (BMI) was calculated as weight (kg) divided by the height squared (m2). Overweight and obesity were defined as a BMI of at least 24kg/m2 and 28kg/m2, respectively, based on the recommendations of the Working Group on Obesity in China.(14)
- Assessment of hypertension and hypertension awareness, treatment, and control
The measurement and definition of hypertension was reported according to the 7th Chinese Joint National Commission guidelines.(15) A standard mercury sphygmomanometer was used by well-trained physicians to measure SBP and DBP on the right arm in triplicate after a 10-minute seated rest. The mean of the three readings was calculated and used in all analysis. Hypertension was defined as having an average SBP ≥ 140 mm Hg and/or an average DBP ≥ 90 mm Hg, and/or a self-reported previous diagnosis of hypertension by a health care provider, and/or taking antihypertensive drugs currently. Awareness of hypertension status was defined as a self-report of any previous diagnosis of hypertension by a health care provider. Treatment of hypertension was defined as a self-reported use of antihypertensive medications at present. Control of hypertension was defined as having an average SBP < 140 mmHg and an average DBP < 90 mmHg while under pharmacological treatment for hypertension.
We compared our results on hypertension prevalence, awareness, treatment, and control rates with results from China Health and Nutrition Survey 2001 (CHNS 2001) and the International Collaborative Study of Cardiovascular Disease in ASIA (InterASIA 2000-2001). Detailed information on these two studies have been reported previously. (16, 17). In brief, CHNS 2001 study was conducted in 31 provinces, autonomous regions and municipalities throughout China. Stratified multistage cluster sampling was used to recruit participants and 141,892 participants ≥18 were analyzed as the final sample size. In the InterASIA study, stratified sampling method was used to select a nationally representative sample of population aged 35-74 years in China during 2000-2001, and 14,989 subjects were included in the analysis. These comparisons can provide evidence on the improvements in hypertension prevalence, awareness, treatment and control over the past ten years and between different samples.
- Statistical analysis
Data were presented as mean SD for continuous and percentages for categorical variables according to gender, respectively. Differences between groups were tested using two-sample student t-tests for continuous variables and the Chi-square test for categorical variables. Multivariable logistic regression models were fit to explore the associations between relevant risk factors and hypertension awareness and treatment.
We also investigated the adjusted associations between independent variables and taking antihypertensive drugs among subjects who were aware of hypertension. Finally, characteristics and proportions of subjects by age groups were analyzed to identify the subpopulations that were more likely to take antihypertensive medications (“adherence”) in the subsample of participants who took treatments for hypertension. All the analysis was done using Stata 15.0 (StataCorp., 2017). P values were 2-tailed and p < 0.05 was considered to be statistically significant.