Nowadays, despite the high prevalence of hypertension, the awareness rate and control rate of this disease are still very low. In addition, the prevalence of hypertension in old population is very high, and most of cases are isolated systolic hypertension (ISH). We investigated people ranging in age from 80 to 99 years in 28 cadre retirement centers in Beijing to study the prevalence and incidence of target organ injury and analyze the relative factors of ISH.
From March 2002 to May 2003, we investigated the blood pressure and hypertensive relative diseases of all the people aged over 80 years in 28 retirement centers for army officers in Beijing. The response rate was 100%.
All the subjects were divided into four age groups: <60, 60-69, 70-79 and ≥80 according to the age when hypertension was diagnosed by a doctor after physical examination. The questionnaire included general healthy state, history of hypertension, the age when hypertension was diagnosed, the awareness rate, the rate of taking antihypertensive drug and control rate, history of cardiovascular disease and diabetes mellitus. Blood pressure was taken three times a day with a mercurial sphygmomanometer in every person, and the mean values were recorded and the relative data were gathered according to questionnaire after the health education. Physical examination forms of the outpatient department and inpatient case history in relative hospitals were analyzed.
Double phase hypertension: systolic blood pressure (SBP) ≥140 mmHg and diastolic blood pressure (DBP) ≥90 mmHg; ISH: SBP ≥ 140 mmHg but DBP<90 mmHg in this time and DBP < 90 mmHg in the past medical history. Diabetes mellitus: fasting serum glucose ≥7.0 mmol/L and 2-hour postprandial serum glucose ≥11.1 mmol/L; impaired glucose tolerance: fasting serum glucose <7.0 mmol/L and 2-hour postprandial serum glucose ≥7.8 mmol/L and < 11.1 mmol/L; hypercholes- terolemia: total cholesterol (TC) > 5.7 mmol/L; hypertriglyceridemia: triglyceride > 1.7 mmol/L; combined hyperlipidemia: total cholesterol (TC) > 5.7 mmol/L and triglyceride > 1.7 mmol/L; chronic renal failure: serum creatinine > 133 μmol/L. The diagnosis of coronary heart disease, heart failure, cerebrovascular disease, disability and dementia were based on the physical examination and medical records.
The trained investigators checked the physical examination records and medical records and then finished the questionnaires.
Data was analyzed using SPSS 10.0 software package. The estimation of confidence interval and test of the comparison between the enumeration data were analyzed through Stata/SE8.0 binomial distribution. A P<0.05 was considered statistically significant.
General healthy state
One thousand and two cases aged 80 to 99 years were enrolled in this study. There were 860 men and 142 women. Eight hundred and thirty-three cases aged 80 to 85 years, 150 cases aged 86 to 90 years, and 19 aged 91 to 99 years.
Prevalence of hypertension
Among the 1002 cases over 80 years old, there were 673 hypertensive patients (total morbidity 67.2%; males 567, females 106), among whom there were 455 ISH (morbidity 45.4%). The incidence of ISH was 67.6% in all hypertensive patients, and 32.4% in double phase hypertension group (according to inquiring their medical history and blood pressure recorded in inpatient cases and physical examination forms and blood pressure taken in this time). Awareness rates were 87.9% and 97.7%, the rates of taking antihypertensive drug were 77.6% and 80.7%, the control rates were 58.7% and 62.8% in ISH and in double phase hypertension group, respectively. There was no significant difference in awareness rate and rate of taking antihypertensive drug and control rate between the two groups. The susceptible age period for ISH was 70 to 79 years, and for double phase hypertension group was less than 60 years (Table 1).
Prevalence of hyperlipidemia
The prevalence of hypercholesterolemia was 13.2% in ISH group, and 12.4% in double phase hypertension group. There was no significant difference between the two groups. The prevalence of hypertriglyceridemia was 11.9% in ISH group and 19.3% in double phase hypertension group. There was significant difference between the two groups(P=0.00; 95%CI RD 2.1990-4.2718). The prevalence of combined hyperlipidemia was 17.8% in ISH group and 17.4% in double phase hypertension group. There was no significant difference between the two groups.
Prevalence of cardiovascular diseases
There was no significant difference in morbidities of coronary heart disease and myocardial infarction between the two groups (81.5% vs 86.7%, 13.4 % vs 12.8%, respectively) (P>0.05). The difference in the incidences of heart failure was significant (4.6 % vs 8.7%, P=0.00; 95%CI RD 7.6863-12.6996)
Prevalence of cerebrovascular diseases
The incidences of cerebrovascular diseases, disability and dementia were higher in double phase hypertension group than those in ISH group (41.5% vs 56.0%, 10.6% vs 16.1%, 8.6% vs 12.8%, respectively) (P=0.00, 95%CI RD 0.2962-0.9448; P=0.00, 95%CI RD 0.5682-1.4794; P=0.00, 95%CI RD 0.2140-0.4348; Table 2). Subgroup analysis showed that there was no significant difference in the incidence of cerebral hemorrhage between the two groups. But the incidences of cerebral thrombosis and lacunar infarction in double phase hypertension group were significantly higher than those in ISH group (Table 2).
Prevalence of diabetes mellitus and chronic renal insufficiency
The prevalence of diabetes mellitus in ISH was significantly higher than that in double phase hypertension group (29.9% vs 24.3%, P=0.0066, 95%CI RD-1.3942-1.4102); there were no significant differences in the prevalence of impaired glucose tolerance and chronic renal insufficiency between the two groups (5.9% vs 6.0%, 13.0% vs 11.0%, respectively; P>0.05).
The result of blood pressure census in 1991 showed that the prevalence of hypertension increased with aging. The prevalence of hypertension in males more than 75 years was 42% and that in females was 51% in China. Syst-China Study1 showed, if taking the blood pressure more than 160/95 mmHg as cut-off point, the prevalence of ISH in 70 to 79 years old group was 12%; that in ≥80 years old group was 19%. Systolic blood pressure increased with aging, but the elevation of diastolic blood pressure gradually slowed down after 60-65 years old. As a result, the pulse pressure increased with aging. So, ISH was the main hypertension type in old people. In British, twenty-three percent of hypertensive patients over 64 years old were double phase hypertension, while seventy-six percent of those were ISH and only one percent were IDH (isolated diastolic hypertension).2 Our study shows that the prevalence of hypertension, especially ISH is very high in patients over 80 years old, and there is no IDH, which is consistent with other large-scale clinical trials. In our study, the prevalence of ISH is significantly higher than that in patients over 80 years old in Syst-China. That is probably due to the difference between the diagnosis criteria in the two studies. The diagnosis criteria in our study for double phase hypertension is over 140/90 mmHg; diagnosis criteria for ISH is SBP ≥140 mmHg and DBP < 90 mmHg.
The ventricular ejection and peripheral resistance are two basic factors for the formation of blood pressure. And the compliance of the aorta is important for the formation of systolic and diastolic blood pressure. The decrease of compliance can result in ISH. Three large-scale clinical trials (SHEP,3 Syst-Europe4 and Syst-China) suggest that compared with diastolic blood pressure, the elevation of systolic blood pressure is a more important cardiovascular risk factor. The morbidity of heart failure, cerebrovascular diseases, disability and dementia are higher in double phase hypertension group than those in ISH group. The results show that the increase of both systolic and diastolic blood pressure is more dangerous than ISH only for very old people. Benetos et al5 and Celis et al6 reported that the influence of ISH was more dangerous than that of IDH and double phase hypertension in the cardiocerebrovascular system. But they did not enroll the very old people. We think that the cardio-cerebrovascular change of very old people have its own characters. The elevated systolic pressure could damage the target organs, besides, the influence from elevated diastolic blood pressure can aggravate this injury and even result in heart failure, cerebrovascular complications, disability and dementia. So, the improvement of small arterial elasticity and the effective control of blood pressure (<140/90mmHg) are very important in very old hypertensive patients for lowering the incidence of target organ injury, improving their life quality and survival rate in the future.
In this study, the prevalence of hypertriglyceridemia in double phase hypertension group is higher than ISH group significantly. But the prevalence of diabetes mellitus in ISH is significantly higher than that in double phase hypertension group. So far, the correlation between the hypertriglyceridemia and double phase hypertension is not clear. Our results may be occasional and need further proving. The causality between ISH and diabetes mellitus is still unknown. In our study, the prevalence of hypertension is high, but the rate of taking antihypertensive drug and the control rate are also high. Maybe this is why the patients live over 80 years. So, active therapy on hypertension in very old person can prolong their lives.
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