Akiko Aihara

Home blood pressure measurement has a stronger predictive power for mortality than does screening blood pressure measurement: a population-based observation in Ohasama, Japan.

Objective To compare the predictive powers of self-measurement of blood pressure at home (home blood pressure measurement) and casual (screening) blood pressure measurement for mortality. Design A prospective cohort study. Subjects and methods We obtained home and screening blood pressure measurements for 1789 subjects aged ≥ 40 years who were followed up for a mean of 6.6 years. The prognostic significance of blood pressure for mortality was determined by the Cox proportional hazards regression model adjusted for age, sex, smoking status, past history of cardiovascular disease, and the use of antihypertensive medication. Results When the home blood pressure values and the screening blood pressure values were simultaneously incorporated into the Cox model as continuous variables, only the average of multiple (taken more than three times) home systolic blood pressure values was significantly and strongly related to the cardiovascular mortality risk. The average of the two initial home blood pressure values was also better related to the mortality risk than were the screening blood pressure values. Conclusions Home blood pressure measurement had a stronger predictive power for mortality than did screening blood pressure measurement for a general population. This appears to be the first study in which the prognostic significances of home and screening blood pressure measurements have been compared.

Relation Between Nocturnal Decline in Blood Pressure and Mortality ☆: The Ohasama Study

To investigate the relation between nocturnal decline in blood pressure and mortality, we obtained ambulatory blood pressures in 1542 residents aged 40 years or over of a rural Japanese community. Subjects were followed-up for a mean of 5.1 years and were then subdivided into four groups according to the percent decline in nocturnal blood pressure: 1) extreme dippers: percent decline in nocturnal blood pressure > or = 20% of the daytime blood pressure; 2) dippers: decline of > or = 10% but < 20%; 3) nondippers: decline of > or = 0% but < 10%; and 4) inverted dippers: no decline. The relationship between the decline in nocturnal blood pressure and mortality was examined by the Cox proportional hazards regression model adjusted for age, sex, smoking status, previous history of cardiovascular disease, and the use of antihypertensive medication. The mortality risk was highest in inverted dippers, followed by nondippers. There was no difference in mortality between extreme dippers and dippers. This relationship was observed for both treated and untreated subjects, was more pronounced for cardiovascular than for noncardiovascular mortality, and did not change after the data were adjusted for 24-h, daytime, and nighttime blood pressure levels.

Factors that affect blood pressure variability. A community-based study in Ohasama, Japan.

Factors that affect blood pressure (BP) variability, ie, standard deviation (SD) and variation coefficient (VC: SD/average ambulatory BP) of ambulatory BP, were examined in a community-based sample in northeastern Japan. Screening and ambulatory BPs were measured in 823 subjects > or = 20 years of age, and the effects of age and BP on the SD and the VC were examined. In bivariate regression analysis, the SD of ambulatory BP was positively correlated with age and the ambulatory BP. The VC was also correlated with age. Both the SD and the VC were strongly correlated with the magnitude of the nocturnal decline in BP. Ambulatory BP was positively correlated with age and negatively correlated with heart rate and the SD of heart rate. Multivariate analysis demonstrated that the nocturnal decline in BP showed the strongest association with the SD and the VC of 24-h BP. However, age and BP were still independently and positively associated with the SD and the VC of ambulatory BP. Furthermore, pulse pressure and BMI were independently and positively associated with the SD and the VC of ambulatory BP. Since the SD and the VC of 24-h ambulatory BP were determined mainly by the nocturnal decline in BP, this variable appears to be an index of the circadian variation in BP and not an index of short-term BP variability. Pulse pressure, an index of arterial stiffness, was a relatively strong predictor of the SD and the VC of BP. In addition, the SD of heart rate, an index of baroreflex function, decreased with increasing age. Findings suggest that the increase in BP variability in hypertensive and elderly subjects may be explained, in part, by a disturbance of baroreflex function associated with an increase in arterial stiffness due to aging and hypertension.

Characteristics of blood pressure measured at home in the morning and in the evening : the Ohasama study

OBJECTIVE To determine the qualitative and quantitative differences of blood pressure measured at home (home measurement) in the morning versus the evening. METHODS Of 3744 participants, aged 20 years or older in the Ohasama population, more than 14 home measurements in the morning and in the evening, respectively, were obtained in each of 1207 individuals (881 untreated, 56.1 +/- 11.4 years and 326 treated, 66.0 +/- 9.2 years). A casual/screening measurement was also obtained in these individuals. RESULTS The home measurements in the morning were significantly higher than those in the evening. The bivariate linear regression analysis demonstrated that the difference between diastolic home measurement in the morning and that in the evening increased with an increase in diastolic home measurements. The multiple step-wise linear regression analysis, however, demonstrated that male sex, the use of antihypertensive medication, and SD of home measurements in individuals (blood pressure variability), but not level of home measurements, were positively associated with the difference between home measurement in the morning and that in the evening. The SD of home measurement in the evening in individuals was significantly larger than that in the morning, and the SD in treated individuals was significantly larger than that in untreated individuals. The correlations between casual and home measurements were moderate in untreated individuals (r = 0.509-0.567) but poor in treated subjects (r= 0.223-0.384). The correlations between home systolic measurements in the morning and in the evening were very close in both treated and untreated subjects (r = 0.814-0.902). The correlations between the SD of home measurements in the morning and in the evening were moderate in both treated and untreated individuals (r = 0.585-0.657). CONCLUSIONS Qualitative and quantitative differences in home blood pressure measurement, due to the differential time of measurement, should be taken into consideration in clinical use of home blood pressure measurements.

Original CommunicationFactors That Affect Blood Pressure Variability: A Community-Based Study in Ohasama, Japan☆

Factors that affect blood pressure (BP) variability, ie, standard deviation (SD) and variation coefficient (VC: SD/average ambulatory BP) of ambulatory BP, were examined in a community-based sample in northeastern Japan. Screening and ambulatory BPs were measured in 823 subjects > or = 20 years of age, and the effects of age and BP on the SD and the VC were examined. In bivariate regression analysis, the SD of ambulatory BP was positively correlated with age and the ambulatory BP. The VC was also correlated with age. Both the SD and the VC were strongly correlated with the magnitude of the nocturnal decline in BP. Ambulatory BP was positively correlated with age and negatively correlated with heart rate and the SD of heart rate. Multivariate analysis demonstrated that the nocturnal decline in BP showed the strongest association with the SD and the VC of 24-h BP. However, age and BP were still independently and positively associated with the SD and the VC of ambulatory BP. Furthermore, pulse pressure and BMI were independently and positively associated with the SD and the VC of ambulatory BP. Since the SD and the VC of 24-h ambulatory BP were determined mainly by the nocturnal decline in BP, this variable appears to be an index of the circadian variation in BP and not an index of short-term BP variability. Pulse pressure, an index of arterial stiffness, was a relatively strong predictor of the SD and the VC of BP. In addition, the SD of heart rate, an index of baroreflex function, decreased with increasing age. Findings suggest that the increase in BP variability in hypertensive and elderly subjects may be explained, in part, by a disturbance of baroreflex function associated with an increase in arterial stiffness due to aging and hypertension.

Altered sympathetic and vagal modulations of the cardiovascular system in patients with pheochromocytoma ☆: Their relations to orthostatic hypotension

To examine sympathetic and vagal cardiovascular regulatory mechanisms in the pathogenesis of orthostatic hypotension in pheochromocytoma, we continuously monitored blood pressure (Finapres) and RR interval (electrocardiogram) in supine and standing positions in 12 patients with pheochromocytoma, 43 patients with essential hypertension, and 30 normotensive subjects. Mayer wave power spectrum of systolic blood pressure variability (approximately 0.1 Hz) and respiratory power spectrum of the RR interval variability (approximately 0.25 Hz) were taken as measures of sympathetic vascular and cardiac vagal modulations, respectively. Systolic blood pressure decreased more upon standing in pheochromocytoma patients (-21 +/- 7 mm Hg) than in normotensive subjects (-5 +/- 2 mm Hg) or essential hypertensive patients (-3 +/- 2 mm Hg) (P < .005 for both), whereas heart rate tended to increase most in the pheochromocytoma group. Postural reduction in systolic blood pressure was highly correlated with postural increase in heart rate (reciprocal change in RR interval) in the pheochromocytoma group (r = 0.716, P < .01) suggesting that baroreflex is well functioning in those patients. The Mayer wave power spectrum in recumbency was extremely depressed in pheochromocytoma patients (1.1 +/- 0.2 mm Hg2) compared with normotensives (4.5 +/- 0.8 mm Hg2) or essential hypertensives (5.6 +/- 0.6 mm Hg2) (P < .001 for both). This parameter increased significantly with standing in all groups but remained lower in patients with pheochromocytoma (5.1 +/- 1.0 mm Hg2) than in normotensives (7.1 +/- 0.9 mm Hg2, P = NS), whereas essential hypertensive patients demonstrated far greater value (19.2 +/- 3.8, P < .01 for both). The respiratory power spectrum of the RR interval in recumbency of pheochromocytoma patients (189 +/- 54 msec2) was less than in normotensive subjects (714 +/- 100 msec2, P < .001) but did not differ from that in patients with essential hypertension (214 +/- 41 msec2). The respiratory power spectrum of the RR interval upon standing was markedly suppressed in pheochromocytoma patients (36.9 +/- 16.7 msec2) compared with normotensive subjects (129.5 +/- 23.6 msec2) or essential hypertensive patients (126.6 +/- 28.6 msec2) (P < .001 for both). Postural decrement in the respiratory power spectrum of the RR interval correlated positively with postural increase in heart rate (r = 0.577, P < .05) in patients with pheochromocytoma. After successful surgery (n = 9), the Mayer wave power spectrum of the systolic blood pressure and the blood pressure response to orthostasis were normalized. These data suggest that altered sympathetic vascular regulation is central to the pathogenesis of orthostatic hypotension in pheochromocytoma, whereas cardiac vagal regulation acts to compensate.

The influence of one-year treatment by angiotensin converting enzyme inhibitor on baroreflex sensitivity and flow-mediated vasodilation of the brachial artery in essential hypertension--comparison with calcium channel blockers.

Background. Both baroreflex sensitivity and flow‐mediated vasodilator function have been recognized to have prognostic significance in cardiovascular diseases. Long‐term antihypertensive treatment effects on these parameters, however, remain unclear. Subjects and Methods. We examined the effects of long‐term treatment by angiotensin converting enzyme inhibitors (ACEI) or calcium channel blockers (CCB) on baroreflex and flow‐mediated vasodilator function in patients with essential hypertension (EH). We recruited 36 patients aged 56 ± 11 years, with systolic blood pressure ≧160 mmHg and/or diastolic blood pressure ≧95 mmHg. Patients were assigned either to treatment by long‐acting ACEI (n = 12) or CCB (n = 24). All patients were followed for 12 months. Optimal BP was achieved by two optional increases in treatment: dose‐doubling of the primary drug during the first three months and the addition of diuretics or β‐blockers thereafter. Target blood pressure was 140/90 mmHg or a fall ≧20/10 mmHg. Baroreflex sensitivity was examined by spectral analysis of blood pressure and RR interval variabilities before treatment and after 3 and 12 months of treatment. The flow‐mediated vasodilator function was determined before and 12 months after treatment by measuring the change in brachial artery diameter during increases in flow induced by reactive hyperemia. Results. Baseline blood pressures were similar between the ACEI and CCB groups (172 ± 5/103 ± 2 vs. 172 ± 4/101 ± 3 mmHg). Blood pressures after 3 and 12 months of treatment also did not differ between the ACEI and CCB groups (149 ± 4/91 ± 2 vs. 145 ± 2/ 85 ± 2 mmHg, and 133 ± 5/84 ± 2 vs. 133 ± 2/81 ± 2 mmHg, respectively). Baseline baroreflex sensitivity was similar between the groups (6.7 ± 0.8 vs. 5.9 ± 0.6 msec/mmHg). This parameter remained unchanged at three months but increased after 12 months of treatment in both the ACEI (9.5 ± 1.6 msec/mmHg, p = 0.05) and CCB (9.1 ± 1.2 msec/mmHg, p = 0.006) groups. Percent increases in brachial arterial diameter and flow during reactive hyperemia increased in the group treated with ACEI (12.4 ± 3.5 vs. 25.8 ± 6.3% and 618 ± 72 vs. 953 ± 166, p < 0.05 for both) but both parameters remained unchanged in the group treated with CCB. Conclusion. These data suggest that long‐term blood pressure control with modern antihypertensive drugs improves baroreflex function. Treatment with ACEI may be more favorable for flow‐mediated vasodilator function than treatment with CCB.

Increased gain in baroreceptor-heart rate reflex in patients with primary aldosteronism.

Objective Reduced baroreflex sensitivity has been reported in several kinds of human hypertension. However, the nature of the baroreceptor-heart rate reflex in hypertension due to excess mineralocorticoid has never been fully explored. Patients and methods Thirty patients with primary aldosteronism, 60 patients with essential hypertension (World Health organization stages I or II) and 45 normotensive subjects were enrolled. The groups did not differ in mean age. Blood pressure was similar between patients with primary aldosteronism and those with essential hypertension. Blood pressure (Finapres) and the RR interval (ECG) were monitored continuously at rest. The closed loop gain between systolic blood pressure and RR interval variabilities was used to measure the sensitivity of the baroreceptor-heart rate reflex. Results Baroreflex sensitivity in the group with primary aldosteronism was significantly greater than in the essential hypertensive group, but did not differ significantly between the group with aldosteronism and the normotensive group. Three to four weeks after removal of an adrenal adenoma (n = 25), both systolic and diastolic blood pressure were decreased significantly in the aldosteronism group but were still higher than in the normotensive group. The baroreflex sensitivity was reduced by about 40% after adrenalectomy compared to pre-operative values. The decrease in the baroreflex gain following adrenalectomy was correlated negatively with the decrease in systolic blood pressure (r = −4.00, P = 0.05). Conclusion These results demonstrate that hypertension due to excess mineralocorticoids is characterized by an increase in the gain of the baroreceptor-heart rate reflex. The reduction in baroreflex gain following adrenalectomy may delay the normalization of blood pressure.

Decreased Blood Pressure Variability at Rest in Patients With Primary Aldosteronism

Increased blood pressure (BP) variability in essential hypertension (EH) is attributed in part to a reduction in baroreflex sensitivity. We previously showed that baroreflex sensitivity is not reduced in hypertension associated with primary aldosteronism (PA) compared with normotensive (NT) subjects. This study examined whether the preservation of baroreflex function in patients with PA would prevent an increase in BP variability. The beat-to-beat BP (measured with Finapres) and RR interval (from electrocardiograms) were monitored for 10 min in the supine and standing positions in 34 patients with PA, 60 patients with EH, and 45 NT subjects. Recordings were also performed during mild ergometer exercise in 7 PA patients, 8 EH patients, and 9 NT subjects. Blood pressure variability was assessed by both standard deviation (SD) and coefficient of variation (CV). Baroreflex sensitivity (BRS) was assessed by the closed-loop gain between systolic BP and RR interval variability. The SD and the CV of systolic BP (SBP) and the CV of diastolic (DBP) BP were significantly smaller in patients with PA than in patients with EH in both supine and standing positions. The SD of SBP and DBP were similar in patients with PA and NT subjects, although the CV were significantly smaller in patients with PA. The BRS was inversely correlated with both the SD and CV for SBP in the supine (r = -0.397 and -0.440, P < .05, respectively) and standing (r = -0.457 and -0.412, P < .05, respectively) positions in patients with PA. Exercise reduced the BRS in all groups (70%, 26%, and 64% for PA, EH, and NT, respectively, P < .01). Blood pressure variability did not change significantly during exercise, compared with rest, in the PA and NT groups but was decreased (P < .05) in the patients with EH. In conclusion, primary aldosteronism is characterized by decreased supine and standing BP variability, which is due in part to the preservation of baroreflex function. Our data further showed that BP variability is minimized by nonbaroreflex mechanisms during mild exercise.