1. The prevalence of hypertension in our population
1.1. Prevalence of hypertension in our population and its changing trend
Over the past 50 years, four large-scale population-based sample surveys on the prevalence of hypertension have been conducted in China. The total number, age, diagnostic criteria and crude prevalence of each survey are shown in Table 1-1. Although the scale, age and diagnostic criteria of each survey are not consistent, they basically reflect the obvious rising trend of hypertension prevalence in our population over the past 50 years in a more objective way. According to the 2002 survey data, the prevalence of hypertension among adults over 18 years of age in China was 18.8%, and it is estimated that there are currently about 200 million hypertensive patients in China, with 2 out of every 10 adults suffering from hypertension, accounting for about 1/5 of the total number of hypertensive people worldwide.
The majority of the hypertensive population in China is mild and moderate hypertension (90%), with mild hypertension accounting for more than 60%. However, the proportion of normal blood pressure (<120/80mmHg) in our population is less than 1/2. The proportion of people with normal high blood pressure level in the total population of the year is increasing, especially in middle-aged and young people, which has increased from 29% in 1991 to 34% in 2002, and is the main source of the continuous increase in the prevalence of hypertension and the sharp increase in the number of patients in China. It is estimated that there are 10 million new hypertensive patients in China every year.
1.2. General pattern of hypertension prevalence in our population
Generally, the prevalence of hypertension increases with age; the prevalence is slightly lower in women than in men before menopause, but rises rapidly after menopause, even higher than in men; the prevalence is higher in high latitude cold regions than in low latitude warm regions, and higher in high altitude than in low altitude regions; related to dietary habits, the higher the salt and saturated fat intake, the higher the average blood pressure level and prevalence.
The prevalence of hypertension in our population has two distinctive features: from the south to the north, the prevalence of hypertension tends to increase, which may be related to the lower average annual temperature in the north and the higher salt intake of the northern population; there are also some differences in the prevalence of hypertension among different ethnic groups, with Tibetans, Mongolians and Koreans living in the north or highland areas having higher prevalence, while Zhuang, Miao and Yi living in the south or non-highland areas have higher prevalence. This difference may be related to geographical environment and lifestyle, but no significant genetic background differences have been found among ethnic groups.
1.3 Important risk factors for the development of hypertension in our population
1.3.1. High sodium and low potassium diets
In the population, sodium (NaCl) intake was positively associated with blood pressure levels and the prevalence of hypertension, whereas potassium intake was negatively associated with blood pressure levels. The correlation between dietary sodium/potassium ratio and blood pressure is even stronger. A study of 14 cohorts in China showed that an average increase in dietary sodium intake of 2 g per day was associated with an increase in systolic and diastolic blood pressure of 2.0 mmHg and 1.2 mmHg, respectively.
Diets high in sodium and low in potassium are the most important risk factors for the development of hypertension in most patients in China. In most areas of China, the per capita daily salt intake is more than 12-15 grams. In the International Collaborative Study of Salt and Blood Pressure (INTERMAP), the 24-hour urinary sodium/potassium ratio, which reflects the amount of dietary sodium/potassium, is above 6 in our population, compared to 2-3 in Western populations.
1.3.2. Overweight and obesity
Body fat content is positively correlated with blood pressure levels. Body mass index (BMI) in the population is positively correlated with blood pressure levels, and for every 3 kg/m2 increase in BMI, the risk of hypertension over a 4-year period increases by 50% for men and 57% for women. A pooled analysis of the follow-up data of 240,000 adults in China showed that the risk of hypertension in those with BMI ≥ 24 kg/m was 3-4 times higher than that in those with normal weight. The distribution of body fat is also associated with the occurrence of hypertension. The more abdominal fat accumulation, the higher the blood pressure level. The risk of hypertension in men with waist circumference ≥90cm or women ≥85cm is more than 4 times higher than that in people with normal waist circumference.
With the socio-economic development and improvement of living standard in China, the proportion and number of overweight and obese people in the population have increased significantly. In the urban middle-aged population, the proportion of overweight people has reached 25-30%. Overweight and obesity will become another important risk factor for the increase of hypertension prevalence in China.
1.3.3. Alcohol consumption
Excessive alcohol consumption is a risk factor for the development of hypertension, and the prevalence of hypertension in the population increases with the amount of alcohol consumed. Although blood pressure decreases for a short period of time after small amounts of alcohol are consumed, long-term small amounts of alcohol consumption can cause a mild increase in blood pressure; excessive alcohol consumption causes a significant increase in blood pressure. If you drink an average of >3 standard glasses of alcohol per day (1 standard glass is equivalent to 12 grams of alcohol, about 360 grams of beer, or 100 grams of wine, or 30 grams of liquor), the systolic and diastolic blood pressure will rise by an average of 3.5mmHg and 2.1mmHg respectively, and the increase in blood pressure will increase with the amount of alcohol consumed.
The number of people who drink alcohol in China is large, and some men with hypertension have a long-term habit of drinking alcohol and drinking strong alcohol, so the effect of long-term excessive alcohol consumption on blood pressure and the occurrence of hypertension should be taken seriously. Alcohol consumption also reduces the efficacy of antihypertensive treatment, and excessive alcohol consumption can induce acute cerebral hemorrhage or myocardial infarction attacks.
1.3.4. Mental stress
Chronic mental stress is also a risk factor for the development of hypertension, and the prevalence of hypertension increases in people who work under high levels of mental stress for long periods of time.
1.3.5. Other risk factors
Other risk factors for the development of hypertension include lack of physical activity. In addition to hypertension, cardiovascular disease risk factors include smoking, dyslipidemia, diabetes mellitus, obesity, etc.
1.4. Awareness, treatment and control rates of hypertensive patients in China
The awareness rate, treatment rate and control rate of hypertensive patients are important indicators reflecting the epidemiology and prevention status of hypertension. According to the two larger-scale sample surveys on the awareness, treatment and control rates of hypertensive patients in China (Tables 1-2) and the changes in the three surveys during 1992-2005 in 15 cohorts, the overall awareness, treatment and control rates of hypertensive patients in China are relatively low. In recent years, through the joint efforts of the whole society, the awareness rate, treatment rate and control rate of hypertension have been improving, but they are still lower than 50%, 40% and 10% respectively. Rural areas are lower than urban areas; men are lower than women; and less economically developed areas are lower than more developed areas.
2. Hypertension and cardiovascular risk
2.1. The relationship between blood pressure and cardiovascular events
There is a strong causal relationship between blood pressure levels and the risk of cardiovascular morbidity and mortality. In a global meta-analysis of 61 population-based prospective observational studies (approximately 1 million people, aged 40-89 years) with a mean follow-up of 12 years, office systolic or diastolic blood pressure was continuously, independently and directly positively associated with the risk of stroke and coronary heart disease events. Blood pressure ranged from 115/75 mmHg to 185/115 mmHg, and the risk of cardiovascular and cerebrovascular complications doubled for each 20 mmHg increase in systolic blood pressure or 10 mmHg increase in diastolic blood pressure.
In the Asia Pacific Cohort Study (APCSC), which included 13 populations in China, office BP levels were also strongly associated with stroke and coronary events; moreover, the association between elevated BP and stroke and coronary events was stronger in the Asian population than in the Australian and New Zealand populations. The risk of stroke and fatal myocardial infarction increased by 53% and 31% for each 10 mmHg increase in systolic blood pressure in the Asian population, compared with 24% and 21% in the Australian and New Zealand populations respectively.
Long-term follow-up found that the incidence of end-stage renal disease (ESRD) increased significantly with higher in-office blood pressure. In severe hypertension, the incidence of ESRD was more than 11 times higher than in normotensive individuals, and up to 1.9 times higher even at high normal blood pressure levels.
The positive association between blood pressure and the risk of stroke and coronary events was further confirmed in ambulatory blood pressure or home blood pressure monitoring studies. These studies also found that not only the mean value of blood pressure is important, but also the circadian rhythm of blood pressure and the variability of blood pressure over days, weeks or even months and years can predict the occurrence of stroke and coronary events independently of the mean value of blood pressure.
2.2. Characteristics of the relationship between hypertension and cardiovascular risk in our population
Population surveillance data in China show that cardiovascular deaths account for more than 40% of all deaths, with hypertension being the leading risk factor, and at least half of the 3 million cardiovascular deaths each year are associated with hypertension.
Population surveillance data also show that the annual incidence of stroke is 250/100,000 and the annual incidence of coronary events is 50/100,000, with the incidence of stroke being five times higher than the incidence of coronary events. In clinical treatment trials, the stroke/myocardial infarction incidence ratio was about 5-8:1 in our hypertensive population and about 1:1 in the western hypertensive population. in recent years, the difference between the incidence of stroke and coronary events is still very significant, despite the rising trend of coronary events. This suggests that stroke is the predominant cardiovascular risk in our hypertensive population and has important implications for the development of more effective prevention and control strategies to reduce cardiovascular risk in our population.
China has accumulated experience in the prevention and treatment of cardiovascular disease in the population. Starting in the 1970s, China’s Shougang carried out population-based prevention and control of hypertension, which led to a significant reduction in the incidence of stroke and was recommended by WHO as a prevention and control model for developing countries in the 1990s.
3. Diagnostic assessment
Diagnostic assessment includes the following three aspects: (1) to determine the blood pressure level and other cardiovascular risk factors; (2) to determine the cause of hypertension and to clarify the presence of secondary hypertension; and (3) to look for target organ damage and related clinical conditions. This leads to a differential diagnosis of the cause of hypertension and assessment of the patient’s degree of cardiovascular risk to guide diagnosis and treatment.
3.1. Medical history
A comprehensive and detailed history of the patient should be obtained, including the following: family history: ask if the patient has a family history of hypertension, diabetes mellitus, dyslipidemia, coronary heart disease, stroke or renal disease; duration of the disease: the time of hypertension, the highest level of blood pressure, whether the patient has received antihypertensive treatment and its efficacy and side effects; symptoms and past history: current and past coronary heart disease, heart failure, cerebrovascular disease, peripheral vascular disease Diabetes mellitus, gout, dyslipidemia, bronchial asthma, sleep apnea syndrome, sexual abnormalities and renal disease, etc. Symptoms and treatment status: history of nephritis or anemia, for example, suggesting renal hypertension; presence of hypokalemia such as muscle weakness and episodic flaccidity, suggesting primary aldosteronism; presence of paroxysmal headache, palpitations and excessive sweating suggesting pheochromocytoma. Lifestyle: dietary fat, salt and alcohol intake, number of cigarettes smoked, physical activity and weight change, etc. Drug-induced hypertension: whether or not taking drugs that raise blood pressure, such as oral contraceptives, gastrosterone, nasal drops, cocaine, amphetamines, steroids, NSAIDs, erythropoietin, cyclosporine, and herbal licorice. Psychosocial factors: including family situation, working environment, education level and any history of trauma.
3.2. Physical examination
Careful physical examination can help detect secondary hypertension clues and target organ damage. Physical examination includes: proper measurement of blood pressure and heart rate, and if necessary, blood pressure in the standing position and extremities; measurement of body mass index (BMI), waist circumference and hip circumference; observation of the presence of Cushing’s face, neurofibromatous skin spots, hyperthyroidism proptosis or lower limb edema; auscultation of the carotid artery, thoracic aorta, abdominal The arteries and femoral arteries are examined for murmurs; the thyroid is palpated; a comprehensive cardiopulmonary examination is performed; the abdomen is examined for enlarged kidneys (polycystic kidney) or masses, and the arterial pulsations of the extremities and neurological signs are examined.
3.3. Laboratory tests
Basic items: blood biochemistry (potassium, fasting glucose, serum total cholesterol, triglycerides, HDL cholesterol, LDL cholesterol and uric acid, creatinine); complete blood count, hemoglobin and hematocrit; urinalysis (urine protein, sugar and urine sediment microscopy); electrocardiogram.
Recommended items: 24-hour ambulatory blood pressure monitoring (ABPM), echocardiography, carotid ultrasound, postprandial glucose (measured when fasting glucose ≥ 6.1 mmol), urine albumin quantification (mandatory for diabetic patients), urine protein quantification (for those with positive protein in routine urine examination), funduscopy, chest X-ray, pulse wave velocity (PWV), and ankle-arm blood pressure index (ABI).
Selective items: For patients with suspected secondary hypertension, the following tests can be selected separately as needed: plasma renin activity, blood and urine aldosterone, blood and urine cortisol, blood free methoxyadrenaline (MN) and methoxynorepinephrine (NMN), blood and urine catecholamines, arteriography, renal and adrenal ultrasound, CT or MRI, sleep apnea monitoring, etc. In patients with comorbid hypertension, perform appropriate brain function, cardiac function, and renal function tests.
3.4 Assessment of target organ damage
The identification of target organ damage (heart, brain, kidney or blood vessels, etc.) in hypertensive patients is important for the assessment of cardiovascular risk and early and aggressive treatment of patients. Subclinical target organ damage is an extremely important intermediate step in the entire disease process from hypertension to the eventual cardiovascular event. The detection of asymptomatic subclinical target organ damage in hypertensive patients using relatively simple, inexpensive, and easily scalable tests is an important component of the diagnostic evaluation of hypertension.
3.4.1. Heart
Electrocardiography can detect left ventricular hypertrophy, myocardial ischemia, cardiac block, or arrhythmias. Recently, it has been reported that aVL lead R-wave voltage is closely correlated with left ventricular weight index and can predict cardiovascular events even when hypertension is not associated with ECG left ventricular hypertrophy. Chest X-rays, which provide insight into the cardiac silhouette, large arteries and pulmonary circulation. Echocardiography, which is superior to ECG in the diagnosis of left ventricular hypertrophy and diastolic heart failure. Other diagnostic methods are used when necessary: cardiac magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA), computed tomography coronary angiography (CTA), cardiac isotope imaging, exercise testing or coronary angiography.
3.4.2. Vascular
Carotid intima-media thickness (IMT) and atheromatous plaque predict cardiovascular events independently of blood pressure levels. There is growing evidence that increased aortic stiffness predicts and assesses cardiovascular risk. Several studies have confirmed that increased pulse wave velocity (PWV) is an independent predictor of cardiovascular events. The ankle/arm blood pressure index (ABI), is effective in screening for peripheral arterial disease and assessing cardiovascular risk.
3.4.3. kidney
Renal impairment is mainly based on elevated serum creatinine, decreased estimated glomerular filtration rate (GFR) or increased urinary albumin excretion (UAE). Microalbuminuria, has been shown to be an independent predictor of cardiovascular events. Patients with hypertension, especially in combination with diabetes mellitus, should have their urinary albumin excretion checked regularly. 24-hour urinary albumin excretion or morning urinary albumin/creatinine ratio is optimal, and a random urinary albumin/creatinine ratio is also acceptable. The estimated glomerular filtration rate (eGFR) is a simple and sensitive indicator of renal function, and can be calculated using the Modified Renal Disease Diet (MDRD) formula or the modified MDRD formula proposed by our authors. eGFR reduction is strongly correlated with cardiovascular events. Increased serum uric acid levels may also have some predictive value for cardiovascular risk.
3.4.4. fundus of the eye
Retinal arteriopathy may reflect small vessel disease. Fundus changes in hypertensive eyes examined by routine fundoscopy are valuable in determining prognosis according to the Keith-Wagener and Backer four-grade classification, grade 3 or 4 hypertensive fundus. High-resolution fundus imaging systems are expected to be a tool for examining small vascular lesions in the fundus.
3.4.5. Brain
Cranial MRA or CTA helps to detect luminal lesions or cerebral vascular stenosis, calcification and plaque lesions. Transcranial Doppler ultrasound (TCD) is helpful in diagnosing cerebral vasospasm, stenosis, or occlusion. Screening assessment of cognitive function is currently performed using the Simple Mental State Examination Scale (MMSE).