Normal blood pressure in 80-year-old people is systolic blood pressure <120 mmHg and diastolic blood pressure <80 mmHg; normal high blood pressure is systolic blood pressure 120-139 mmHg and diastolic blood pressure 80-89 mmHg mmHg. In the absence of anti-hypertensive drugs, blood pressure was measured once a day for three days, respectively, and if systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg, it can be diagnosed as hypertension. Patients with a previous history of hypertension, who have received regular blood pressure lowering treatment, are diagnosed with hypertension despite a blood pressure <140/90 mmHg. Blood pressure levels are continuously normally distributed in the population, and there is no clear boundary between normal blood pressure and elevated blood pressure, and the criteria for hypertension are defined based on clinical and epidemiological data. (Chinese hypertension prevention and treatment guideline criteria: Currently, China uses normotension (systolic blood pressure <120 mmHg and diastolic blood pressure <80 mmHg), normal high [systolic blood pressure 120-139 mmHg and/or diastolic blood pressure 80-89 mmHg] and hypertension [systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg] for blood pressure level classification.) Hypertension was further classified into three classes according to the level of elevated blood pressure. Class I hypertension (mild) is systolic blood pressure 140-159 mmHg and/or diastolic blood pressure 90-99 mmHg; Class II hypertension (moderate) is systolic blood pressure 160-179 mmHg and/or diastolic blood pressure 100-109 mmHg; Class III hypertension (severe) is systolic blood pressure ≥180 mmHg and/or diastolic blood pressure ≥110 mmHg. (Note: When systolic and diastolic blood pressure are classified (Note: When systolic and diastolic blood pressure are in different grades, the higher classification prevails.) The above criteria apply to men and women over 18 years of age, while children use the 95th percentile of blood pressure values for different age groups, usually below adult levels. It should be noted that the above blood pressure values are office blood pressure, and in the case of home self-measured blood pressure, the diagnostic criteria for hypertension is ≥135/85 mmHg, which corresponds to the office blood pressure of 140/90 mmHg.