| BackgroundAs the most important risk factor of cardiovascular disease, the top killer of Chinese population, hypertension has become a huge public health challenge in China. In the setting of rapid and unbalanced socio-economic development in the last decade, understanding the current prevalence of hypertension and its awareness, treatment and control both at national and local level, and to explore the underlying reasons for spatial differences are conducive to tailoring national or region health policy.ObjectivesThe study aimed to assess national and provincial prevalence of hypertension and its awareness, treatment and control rates among Chinese adults, to measure multilevel spatial heterogeneity of those hypertension related indicators and determine to what extent the heterogeneity can be explained by individual characteristics and contextual factors.MethodsThe data of the study was extracted from the 2013-2014 survey of China Chronic Disease and Risk Factors Surveillance. The survey collected information on demographic characteristics, socio-economic status, lifestyle related behavioral risk factors, hypertension management, and objectively measured height, weight, systolic blood pressure, and diastolic blood pressure from a random sample from 297 counties/districts in 31 provinces of mainland China selected by multi-stage stratified clustering sampling method. A total of 174,621 permenent residents aged 18 years or over were included in the analysis. The age and sex distribution, seasonal variation of systolic and diastolic blood pressure were assessed. National prevalence of hypertension and related rates of awareness, treatment and control were calculated and compared by age, sex, region, survey season and other demographic and socio-economic factors, along with estimation of total number of hypertension in China using 2010 Census data. We also estimated the prevalence of hypertension, awarenss, treatment and control for each province, and explored geographic variation and clustering at provincial level. Multilevel modelling were used to disentangle person and area-level contributions to the variation in each of the outcome variables.We calculated sampling weights per the sampling scheme and poststratification factor by provincial population data from the 2010 census. Design based analysis was performed to obtain the national and provincial prevalence. Taylor series linearization was used to estimate the sampling error and to construct the 95% confidence interval (95% CI). Least squared estimation was adopted to improve comparability of by-group comparisons of prevalence, where age, sex, residence location and survey season were adjusted. Design based logistic regression was used to test the differences among subgroups and the trend of the prevalences along age, education level and income level. The spatial variance was measured by median odds ratio derived from empty model of five-level logistic regressions. Step-wise multi-level modelling techniques were used to explore the contribution to the spatical differences from independent variables.ResultsOverall, the mean (standard deviation) of systolic and diastolic blood pressure was 127.8 (20.0) and 76.5 (11.4) mmHg, respectively, and 27.8% of population aged≥ 18 years were hypertensive. Of those with hypertension,31.9% were previously diagnosed, of those diagnosed 82.9% were treated, and of those treated,34.6% had their blood pressure properly controlled (systolic and diastolic blood<140 mmHg and diastolic blood pressure< 90 mmHg), resulting in an overall control rates of 9.7% among those with hypertension. During 2013-2014, an estimated 290 million adults aged≥ 18 years in China had hypertension, representing an absolute increase of 140 million hypertensive individuals since year 2002, and 260 million adults with hypertension failed to have their blood pressure controlled.With adjustment of age, sex, urban/rural, or survey seasons, prevalence is higher in men than in women (34.5% vs 29.5%), highest in winter and lowest in summer, is increasing steeply with rising age, while decreasing with higher education attainment. Although the adjusted prevalence of hypertension differed little, the awareness, treatment and control were much better in urban areas, resulting in a twofold discrepancy in adjusted control rate between urban and rural residents (10.1% vs 5.5%;.P＜0.01). Among hypertensive individuals, older age, higher levels of education or household income tended to be associated with better awareness, treatment and control rates (all P<0.05).Population weighted prevalence of hypertension was found highest in Liaoning province (37.7%,95%C:35.1-40.2%), and the neighbored provinces in northeast and the north region of China also had relative high prevalence. The lowest hypertension prevalence was in Hainan province (18.0%,95%CI:14.3-21.7%), and provinces in the south and northwest region had lower prevalence relative to other parts of China. We failed to found the provincial distribution of awareness rate follows any specific pattern. Hypertension treatment and control were both better in Shanghai, Zhejiang, Beijing and Tianjin, yet poor in western provinces such as Tibet, Yunnan, Guizhou, and Guangxi. After adjusting age, sex, residency location and survey season, the least squared prevalence of hypertension, awareness treatment and control varied markedly across the China. At provincial level, we found 2-fold differences in adjusted prevalence of hypertension (Beijing—42.2% vs Hainan — 19.1%), rate of awareness (Shanghai — 39.0% vs Shandong — 17.6%) and the percentage of treatment among those who were aware of their hypertension (Shanghai — 94.4% vs Tibet — 43.6%). We also found 3.5-fold variation in provincial treatment rate (Shanghai — 35.7% vs Tibet 10.2%),3-fold variation in control among treatment (Zhejiang — 50.0% vs Liaoning — 16.8%) and 6.2-fold variation in the overall control rate (Shanghai — 16.1% vs Liaoning — 2.6%).The multilevel analysis indicated that varying spatial heterogeneity of hypertension existed at level of province, county, township and village, with median odds ratio (MOR) ranging from 1.19-1.35; variation of awareness (MOR range:1.27-1.33) and control (MOR range:1.29-1.45) among treatment existed at provincial, county and township level; while treatment among awareness varied at only provincial (MOR=1.60) and county level (MOR=1.62).Differences in Individual age and sex explained 25.3% of provincial variation,17.4% of township level variation and 45.7% of village level variation in hypertension diagnosis, while individual lifestyle risk factors, health literacy and health care seeking behavior explained 38.4% of provincial variation in diagnosis. Differences in individual socio-economic status accounted for more variation than that of age and sex in provincial and township level variation in awareness, and differences of individual age and sex explained more provincial variation in awareness than individual socio-economic status. Each group of covariates explained to some extent of variation in hypertension treatment among awareness at all levels. With regard to the control among treatment, the final model explained a moderate proportion of variation, but the contextual factor (like county average years of education) contribute a non-trivial part to the variation at both provincial (11.5%) and county level (12.5%).ConclusionChina is now facing a serious situation of hypertension prevention and control, and possible daunting burden of cardiovascular disease in the future. It is extremely urgent to take effective measures to improve hypertension awareness, treatment and control among the hypertensives.There were notable variations across the China in provincial prevalence of hypertension, awareness, treatment and control. Provincial specific strategy for hypertension prevention and control is necessary. In particular, for the populous provinces with a high hypertension prevalence and poor control, reasons should be carefully investigated and prompt public health responses are needed.Individual lifestyle behavioral risk factors, socio-economic status, health literacy and health-care-seeking behaviors were associated with spatial variation in hypertension diagnosis, awareness, treatment and control, and to some extent explained those spatial variation. Contextual factors were also related to those hypertension indicators, indicating establishing supporting context may help improve hypertension prevention and control.
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