To the best of our knowledge, this study presents the latest reliable information about the epidemiological situation of hypertension in Inner Mongolia, the largest province in northern China. In the first and largest population survey in Inner Mongolia, we precisely estimated the level of blood pressure, the current situation of hypertension, and the disease burden of hypertension in Inner Mongolia. In northern China, Inner Mongolia, the rates of prevalence, awareness, treatment, control and control under treatment for hypertension was 55.7%, 52.8%, 43.3%, 8.6% and 19.8%, respectively. And the rates of prevalence, awareness, treatment, control and control under treatment for hypertension varied widely across the various subgroups, from 32.6% to 75.1%, from 35.7% to 76.2%, from 24.9% to 64.6%, from 3.9% to 20.4%, and from 11.2% to 31.6%.
We found that hypertension with high prevalence and low control in northern China, which was similar to the results of other previous studies from in Inner Mongolia and northern China11,17-20. And compared with studies from high-income countries21,22，we observed higher prevalence and lower control rates of hypertension in northern China. Likewise, we found that the age- and sex-standardized rates of hypertension prevalence were higher than those in a 2017 report from national report (49.4% vs. 37.2%)10. The higher prevalence of hypertension were found in our study could be explained by obesity and high-salt diet, which were the main factors associated with hypertension. As well known, high-salt diet is common in Inner Mongolia. A survey in Inner Mongolia showed that the salt intake was 12.9 g/d, which was higher than the 7-8 g/d in southern China, and twice more than the recommended salt intake (less than 5 g/d) by World Health Organization (WHO)23. The Global BMI Mortality Collaboration reported that overweight and obesity significantly increased the risk of all-cause death in the global population24, and were important risk factors for hypertension4,25,26 The obesity rate in this study was 24.9%, while the national study in the same period reported that the obesity rate of the 35-75years old population was 15.7%10. In addition, we found that most of the hypertension patients in the study were unaware and treated but not controlled. Even a study conducted in 44 low-income and middle-income countries showed that the lowest control rate of hypertension was 11.3% in Belize27, which was higher than our study results (8.6%). And the rate of control under treatment for hypertension only was 19.8% in our study. Therefore, it is necessary to improve the discipline level and service capabilities of the grassroots units in Inner Mongolia by standardizing the procedure of diagnosis and comprehensive treatment and implementing comprehensive management and control strategies.
We found the obesity were associated with better blood pressure awareness, treatment and control among hypertensive patients. These findings are in agreement with He et al.’s reports28. It has been suggested that obesity positively influence blood pressure checking and prescription of medication for intervention, hence, higher awareness, treatment and control levels.
The mean SBP and DBP was 140.5 mmHg and 84.8 mmHg in Inner Mongolia, respectively. The results of a cohort study showed that the mean blood pressure in northern China was SBP 122.7/DBP 80.0 mmHg and in southern China was 117.0/75.7 mmHg. Compared to our results, one study conducted in Jilin Province25, which located in northern China and had similar economic level to Inner Mongolia, showed lower blood pressure level (130.5/85.0 mmHg in male, 128.3/81.7 mmHg in female). The difference in blood pressure between our study and other studies may partly attributed to the different age and eating habits of the study populations. In addition, we found that uncontrolled hypertension who were treated and untreated had a large distance to the target values of SBP, the distance were 18.0 (8.0-30.5) mmHg and 10.5 (3.0-20.5) mmHg, respectively. The results showed that populations had higher blood pressure in Inner Mongolia, especially SBP. A study has showed that the highest risk factor attributed to global death in 2019 was high SBP, which accounted for 19.2% of the total deaths5. There was closely causal relationship between blood pressure and the incidence and death of cardiovascular and cerebrovascular diseases. The SBP of Asians increased by 10 mmHg, and the risk of stroke and myocardial infarction increased by 53% and 31%, respectively29. Therefore, achieving the treatment targets of blood pressure is a great challenge and very urgent in Inner Mongolia.
Our study showed that the older age was a factor associated with hypertension. Although participants of the 35-44 age group had the lowest prevalence of hypertension in our study, their prevalence was higher than the national prevalence of hypertension (32.6% vs. 22%), and the 35-44 age group constituted the largest proportion of populations with high normal blood pressure. If the blood pressure of these populations was not well controlled, it will further increase the burden of hypertension. Notably, younger patients had lower awareness, treatment and control rate of hypertension, but they had higher control under treatment rate of hypertension. Compared with older adult patients, younger patients lack health awareness, have fewer consultations with clinicians, have more bad habits, are less likely to adhere to prescribed medications, but they have lower blood pressure levels. If younger patients can adhere to regular medication, blood pressure can be well controlled. Moreover, most guidelines advocate screening for blood pressure from a relatively young age30. However, in our study, the participants of 35-44 age group had the lowest hypertension awareness rate. Thus, screening strategies need to be designed to appeal to individuals of young age.
The results of research on the relationship between smoking, drinking and hypertension are inconsistent31-33. Some studies showed that smoking had no clear relationship with hypertension. Many studies had shown that hypertension was related to the level of alcohol consumption32. However, our study demonstrated that current smoker was a protective factor for hypertension. This can be attributed to the fact that cross-sectional studies cannot determine the sequence of cause and effect and that more hypertension tend to change bad lifestyles, such as quitting smoking. Several studies have found that the risk of hypertension is much higher among male than female, and hypertension awareness, treatment and control in female is higher than in male, which was consistent with our research results34,35. Compared to female, male are less concerned about health and have more bad habits. Male visit the doctor less often, have shorter consultations, and tend to see their physician later in the course of their illness than female36. Moreover, we found rural-urban and ethnicity disparity in the prevalence and control of hypertension. Compared with urban areas, the hypertension with higher prevalence and lower awareness, treatment and control in rural areas. This suggests that patients with hypertension in rural areas groups should be given more attention in promoting awareness, treatment and improving the management of hypertension.
Because Mongol was the main minority ethnic group in Inner Mongolia, ethnicity of participants was categorized into three groups including Han Chinese, Mongol, and other minority ethnic groups. We found that the crude prevalence rate of Mongol populations was higher than Han populations (52.7% vs 56.0%), but there was no statistically significant difference of the age- and gender-standardized rate (48.0% vs 48.7%) in Inner Mongolia (Additional file 1). However, researches by Li et al26,37. showed that Mongol populations have a higher prevalence of hypertension than Han populations. Different ethnic-specific genetic susceptibility, environmental exposures and the interactions between gene and environment may account for the different prevalence of hypertension38. A study conducted in Inner Mongolia showed that rs13306673 is a genetic factor for hypertension in the Han population but not in Mongolian population39. A further study between the hypertension and ethnic specific genetic susceptibility is urgently needed to clarify the observation.
In Inner Mongolia Autonomous Region, primary health services are in a state of higher demand for health services, but the utilization and resource allocation of primary health services are at a lower level than whole country40. Therefore, the investment in the resources of the primary health service system and the utilization rate of services in the study region should be improved. Moreover, the system of tiered diagnosis and treatment for hypertension, has not been developed in Inner Mongolia, which could contribute to the standardized management of hypertension and enhance the efficiency of utilization of primary health resources. Actually, in the Inner Mongolia Autonomous Region, it is necessary to increase the input of health resources in healthcare institutions at all levels, strengthen regional health planning, so as to further rationally and optimize the allocation of medical resources, taking into account the needs of health services and the needs of health services.