Prevalence, awareness, treatment and control of hypertension and sodium intake in Jiangsu Province, China: a baseline study in 2014

Our study has found that the hypertension prevalence of residents in Jiangsu province was 33.0 % in 2014, as a result, one hypertensive patient was potentially detected from three residents aged from 18 to 69 years old in Jiangsu province. In former studies, the prevalence of hypertension in Chinese population increased significantly from 1991 to 2009 [11], while another surveillance data from Chronic Disease and Its Risk factors Surveillance in China also confirmed this characteristic in Jiangsu province that the standardized rates of hypertension prevalence in residents aged more than 15 years old in 2002, 2007 and 2010 was 25.1, 33.8 and 38.6 %, respectively [17]. In brief, these surveillance data all indicate a tendency of rising hypertension burden in China and Jiangsu province in recent years; Although comparing these hypertension prevalence directly is unsuitable, such level of hypertension is still too high to be paid enough attention by the government. It is also shown in former study in Chinese population that the prevalence was higher in successive age groups [18], so ageing of population may increase this rising tendency. In conclusion, our results suggest that hypertension prevalence rate is still in high level in 2014, which remains a provincial public health problem.

It was also found that hypertension prevalence of the male was higher than that of the female. Indeed, we found that the current smoking rate was significant higher in men than in women, and there were more people overweight and obese in the male. Because smoking and BMI status are found as risk factors of hypertension [19], tobacco reduction and body weight control must be firstly introduced in future policy formulated by the local government.

Former studies at the national level have discovered that hypertension among rural population increased faster than urban population from 2002 to 2010 [20]; In 2014, the hypertension prevalence in urban residents was lower than in rural residents in Jiangsu province; These all suggest that hypertension is more prevalent in rural areas. Economic improvement may be an important reason of this phenomenon, economic improvement in rural areas of China have deeply changed the living standard and economic capacity of the residents there, and risk factors grow dramatically. For instance, obesity and overweight of rural population were increasing faster than those of urban residents by improvement of economic capacity [21].

The control of blood pressure to normal level can reduce the risk of cardiovascular diseases and prevent these vascular events [22]. Our study have found that among those aware of their hypertension condition, blood pressure control rate of the whole Jiangsu residents was still low, only 23.7 % which was even lower than that of neighboring Shangdong province (43.2 %), and much lower than that found in the United States [23, 24]. The comparisons on hypertension awareness and treatment of population in different areas and with different sexual distinctions also derive an imbalance, which mainly include the rural and the male have much lower awareness and treatment level.

The control of hypertension is closely related to the factors such as, awareness of blood pressure level, the technical levels of medical staffs, patients’ medication adherence and life styles [9]. Firstly, the hypertension awareness of those residents who were classified as hypertension was rather low, so the undiscovered hypertensive patients accounted for a significant proportion, which indicate that the examination of hypertension is not still fully covered by current health service. Secondary, current self-reported anti-hypertension medication rate (88.4 %) was optimistic and acceptable, reflecting that high accessibility of treatment services have developed in Jiangsu province. At last, the hypertension control rate (23.7 %) was still low among those who underwent anti-hypertension medications, probably, treatment methods and patients’ medication adherence co-influenced the effect of therapy. In brief, both the blood pressure screening and the effect of medication should be emphasized to increase hypertension control in policies of the future National Salt Reduction Action.

In our survey, we found that the mean of salt consumption converted from urinary sodium in 24-h urine collection was 11.0 g, and only 8.6 % of all residents’ salt intake was below the recommended level (6 g) according to the dietary intake guidelines of Chinese residents [7]. The attention of salt reduction for hypertension control has been increasing throughout the world [25], and the World Health Organization (WHO) has recommended that adults consume no more than 5 g of salt per day (equivalent to 2000 mg of sodium) in 2003 [26]. In addition, total salt intake in our study would be estimated to 12.2 g when considering that approximately 10 % of sodium was excreted in sweat and feces, so excess sodium intake is prevalent in Jiangsu province.

To develop future intervention for control of hypertension, we need to combine our findings and those in other studies to adopt one advance and comprehensive method. Interestingly, the association between residents’ knowledge and attitudes of salt and their behaviors of actual salt consumption is not clear, which suggests that interventions focused only on knowledge, attitudes and behaviors may be of limited efficacy [27]. As being a traditional measure, a single intervention by a health care provider, such as the propaganda of high blood pressure knowledge, can positively impact lifestyle choices, but the extent of this impact was relatively small [28]. So a combination with salt reduction action should draw the attention of governments, and compulsory measure should be put to use. In fact, despite modest effect of dietary sodium restriction cultivated by government, the diet without addition of salt significantly decreased systolic and diastolic BP, and it should be advised for every hypertensive patient [29].

In other country, a gradual sodium reduction (10–15 % over multiple years) strategy leading to the adjustment of salt taste of the population was found valid and suitable [30]. In England, packaged food producers were the main salt using departments [31]. Differently, the major sources of sodium intake are condiments added during house cooking in China [32], so health education and health promotion should widely affect cooking habits of many housewives, such as the generation of quantitative salt spoon.

For the people unwilling or fail to taste ease, low sodium salt as an alternative is undoubtedly more attractive. A kind of salt with reduced sodium and increased potassium is now being used in northern Chinese provinces [33]. Salt substitute might be a perfect strategy to reduce sodium consumption and control hypertension. The interdependency of Na and K in the pathogenesis of hypertension indicates that Na restriction and increased K intake are important strategies for the primary prevention and treatment of hypertension and its cardiovascular consequences [32].

It was the first time to conduct large scale investigation of 24-h urinary samples in Jiangsu province. Our team has established an impeccable quality-control system for all links, which is valuable for future population studies. However, our study has also faced several limitations. Firstly, large representative sample was difficult to be involved in our completed survey. Non-responding participants were not substituted by randomly selected individuals. Only 6 counties were selected around the whole province in the first sampling stage, which also made the uncertainty bigger in estimation of 95 % CI. Secondly, the stability of electronic sphygmomanometer is not as reliable as mercurial sphygmomanometer, and blood pressure measurements on a single occasion (although 3 measurements were taken on that 1 occasion) could not substitute a clinical diagnosis of hypertension. These all increased the bias in blood pressure level measurement. Lastly, creatinine was used to substitute PABA as the biomarker for judging the completeness of 24-h urinary samples, which might have resulted in the inclusion of noneligible samples or the exclusion of eligible samples.