Naoyoshi Minami

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.

Prediction of mortality by ambulatory blood pressure monitoring versus screening blood pressure measurements : a pilot study in Ohasama

Objective To compare the prediction of mortality by ambulatory blood pressure monitoring and screening blood pressure measurements in a general population. Design A prospective cohort study. Patients and methods We obtained blood pressure data for 1542 subjects (565 men and 977 women) aged ≥ 40 years who were followed up for up to 8.1 years (mean 5.1 years). Subjects were subdivided into five groups according to their ambulatory and screening blood pressure levels. The prognostic significance of blood pressure for mortality was examined by the Cox proportional hazards regression model. Results The association between blood pressure level and mortality was more distinctive for the ambulatory blood pressure than it was for the screening blood pressure. The risk of cardiovascular mortality increased significantly for the highest quintiles of 24 h ambulatory blood pressure, whereas there was no significant association between the screening blood pressure and the cardiovascular mortality. When both 24 h and screening blood pressure values were included in the Cox model, only the systolic ambulatory blood pressure was related significantly to the increased risk of cardiovascular mortality. Conclusions The ambulatory blood pressure had a stronger predictive power for mortality than did the screening blood pressure. This appears to have been the first study of the prognostic significance of ambulatory blood pressure monitoring versus screening blood pressure measurements in a general population.

Proposal of Reference Values for Home Blood Pressure Measurement: Prognostic Criteria Based on a Prospective Observation of the General Population in Ohasama, Japan

The purpose of this study was to propose reference values, from a viewpoint of prognostic significance, for blood pressure (BP) measured at home with a semiautomated device (home BP measurement) to differentiate normotension and hypertension. We obtained home BP measurements for 1,913 population-based subjects aged 40 years and over in a rural Japanese community and followed up their survival for a mean duration of 5.0 years. There were 141 deaths during the follow-up period. The association between baseline BP values and the overall mortality was examined by Cox proportional hazards regression model, adjusted for age, gender, and the use of antihypertensive medication. The results indicated that the predictive power of home BP level for subsequent mortality was stronger than that of casual screening BP. There was a linear association between home systolic BP and mortality. The association between home diastolic BP and mortality was nonlinear and well approximated with the secondary degree equation of diastolic BP values. Based on this relation, we propose that the reference value for hypertension is 137/84 mm Hg, and normotension is below 137 mm Hg for home systolic BP and between 66 and 83 mm Hg for home diastolic BP. Home diastolic BP below 66 mm Hg should be considered as low diastolic blood pressure. In this population, home systolic BP of 137 mm Hg and home diastolic BP of 84 mm Hg corresponded to the 80th and 87th percentiles, respectively. Then, 29% of the subjects were classified as having hypertension, 52% as normotension, and 19% as low diastolic blood pressure. All previous studies proposing reference values for home BP measurement, derived from cross-sectional observations, were based on the statistical distribution of home BP values. The reference value must, however, be the one that best predicts the risk for morbidity and mortality from hypertension-related complications. This is the first report proposing reference values for home BP measurement based on prognostic criteria.

Altered circadian blood pressure rhythm in patients with Cushing's syndrome.

The circadian blood pressure rhythm was compared in patients with Cushings syndrome, essential hypertension, and primary aldosteronism. In patients with essential hypertension or primary aldosteronism, a clear nocturnal fall in systolic and diastolic blood pressure and heart rate was observed. This fall was seen in untreated subjects as well as in patients receiving combined treatment with a calcium antagonist, diuretic, converting enzyme inhibitor, alpha-blocker and beta-blocker, or sympatholytic drug. In these groups, there was a positive correlation between heart rate and systolic or diastolic blood pressure. On the other hand, in patients with Cushings syndrome, there was no nocturnal fall in blood pressure but in some patients a rise was observed. In all patients there was a nocturnal fall in heart rate. Thus, there was no significant correlation between heart rate and blood pressure in these patients. Exogenous glucocorticoid eliminated the normal nocturnal fall of blood pressure in patients with chronic glomerulonephritis or systemic lupus erythematosus. These results suggest that the changed circadian blood pressure pattern in patients with Cushings syndrome is not due to antihypertensive treatment or to the mineralocorticoid excess accompanying this disease, but it is attributable to excess glucocorticoid or the associated disturbance in the adrenocorticotropic hormone-glucocorticoid system (or both). This conclusion also implies that the normal circadian rhythm of blood pressure may be regulated at least in part by the adrenocorticotropic hormone-glucocorticoid system.

Ambulatory blood pressure of adults in Ohasama, Japan.

We performed a cross-sectional study in a small town in northern Japan to evaluate the distribution, reference values, and daily variation in ambulatory blood pressure. A total of 705 subjects (229 men aged 61.3 +/- 13.4 years [mean +/- SD] and 476 women aged 57.5 +/- 13.3 years; 41.1% of the regional adult population, n = 1716), including those treated with antihypertensive drugs (n = 231, 66.5 +/- 9.5 years) as well as untreated subjects (n = 474, 55.0 +/- 13.5 years), participated in the study. Both ambulatory and screening blood pressures were measured in 659 subjects. Ambulatory blood pressure was measured with an automatic device (Colin ABPM-630). The 24-hour ambulatory blood pressure in the total population was 121.7 +/- 13.0/71.1 +/- 7.6 mm Hg (95th percentile value [95%] = 146/85 mm Hg). The corresponding value in the untreated subjects was 119.4 +/- 12.5/70.1 +/- 7.4 mm Hg (95% = 144/83 mm Hg). The 24-hour average ambulatory blood pressure was 118.0 +/- 11.1/69.4 +/- 6.8 mm Hg (95% = 139/81 mm Hg) in subjects identified as normotensive by their screening blood pressure (n = 448, 57.2 +/- 13.1 years) and 133.6 +/- 14.2/78.9 +/- 8.8 mm Hg in those identified as hypertensive by their screening blood pressure (n = 73, 63.1 +/- 10.6 years). Based on the mean+SD of the 24-hour ambulatory blood pressure in the normotensive subjects by their screening blood pressure (129/76 mm Hg), the 24-hour ambulatory blood pressures in 25 (34.2%) of these 73 hypertensive subjects by screening blood pressure were below this level. Nine (2%) of 448 normotensive subjects by screening blood pressure were above the mean+2 SDs (140/83 mm Hg) of the 24-hour ambulatory blood pressure in the normotensive group by screening blood pressure. Ambulatory and screening blood pressures increased with age. The age-dependent increase in ambulatory blood pressure was less apparent in men. The 24-hour average pulse rate decreased with age. The daily variation in ambulatory blood pressure (standard deviation) increased with age, whereas that of pulse rate decreased with age. Increases in blood pressure variation were observed in nighttime and daytime blood pressure values. The differences between day versus night ambulatory blood pressures decreased with age in men but not in women.(ABSTRACT TRUNCATED AT 400 WORDS)

Characteristics of a community-based distribution of home blood pressure in Ohasama in northern Japan.

Objective: To evaluate the distribution, reference values and day-to-day variation of blood pressure of untreated subjects measured at home Design: Cross-sectional study of a cohort Setting: General community in northern Japan Subjects: Blood pressure was measured in 871 subjects (mean±SD age 46.0±19.5 years, range 7-98, constituting 38.7% of the local population of Uchikawama region, Ohasama) who were not receiving antihypertensive medication Methods: Subjects measured their own blood pressure at home at least three times (mean±SD 19.718.4) each morning using a semi-automatic oscillometric blood pressure measuring device. Screening blood pressure was measured once. Main outcome measures: Distribution of home blood pressure in the study population as a whole and with respect to age and sex, and the distribution of day-to-day variation of home blood pressure were determined Results: Mean home blood pressure was 117.3±13.4/69.3±9.7mmHg (95% confidence interval 116.4-118.2/68.7-70.0). The 95th centile value was 143/85 mmHg, mean + SD 131/79 mmHg and mean + 2SD 144/89 mmHg. Mean screening blood pressure was 126.2 ±18.9/72.1 ±11.7 mmHg (95th centile 159/92 mmHg). Age- and sex-specific 95th centile values as well as mean±SD were obtained. Mean + SD, mean + 2SD and the 95th centile values obtained as reference upper limits of home blood pressure from subjects identified as normotensive by screening blood pressure (n=707) were 125/77, 137/86 and 134/83 mmHg, respectively. Home blood pressure increased gradually with increasing age in both men and women, although blood pressure was significantly higher in men until 50 years of age. Day-to-day variation of home systolic blood pressure also increased with age Conclusions: Since the distribution of home blood pressure values was affected by age and sex, age- and sex-matched reference values for home blood pressure should be established. Home blood pressure values in elderly subjects should be evaluated carefully, since these exhibit greater day-to-day variation

Clinical evaluation of semiautomatic and automatic devices for home blood pressure measurement: comparison between cuff-oscillometric and microphone methods.

The accuracy and reliability of blood pressure (BP) values were evaluated by comparing values obtained with eight automatic or semiautomatic devices designed for home BP measurement (four microphone devices based on the Korotkoff-sound technique and four cuff-oscillometric devices) with those obtained by the auscultatory method, using a standard mercury sphygmomanometer. Systolic blood pressure (SBP) values obtained using the microphone devices coincided well with those obtained by the auscultatory method. However, these devices produced a certain proportion of errors in the measurement of diastolic blood pressure (DBP), sometimes resulting in recordings at least 25mmHg higher than those obtained by the standard method. The most frequent causes of this phenomenon were an auscultatory (silent) gap and a weak Korotkoff sound after phase IV. A microphone device using a condenser microphone built into the manometer displayed comparatively good acoustic characteristics for determining DBP. All cuff-oscillometric devices demonstrated minimal mean differences and a constant s.d. of mean difference for DBP, with no great differences from the auscultatory method. However, mean differences and s.d.s in SBP measurements using cuff-oscillometric devices were relatively greater than those obtained using some of the microphone devices. Furthermore, the direction of the mean differences in measurements from those obtained with the auscultatory method differed. The error in relation to the auscultatory method tended to be reproducible in the same subjects with both the microphone and the cuff-oscillometric devices. These results indicate that practitioners should select the most appropriate method and/or device by taking into account the factors which may cause measurement error in relation to the auscultatory method in each subject, and should then evaluate, at least once, the difference in BP values obtained using the auscultatory method and using the device. In future, home blood pressure measurement devices for determination of SBP should employ a microphone method, while a method which combines a microphone with a cuff-oscillometric device, thereby compensating for the disadvantage of the Korotkoff-sound signal with the pulse wave signal, should be recommended for measurement of DBP.

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.

Reproducibility of Home Blood Pressure Measurements Over a 1-Year Period

We compared the reproducibility over time of blood pressure measured at the health examinations (screening blood pressure) and blood pressure measured at home (home blood pressure). Both screening and home blood pressure were measured in subjects of a rural community. Subjects measured their own blood pressure at home once in the morning using a semiautomatic oscillometric blood pressure measuring device at least three times (on at least 3 days) in each of two 4-week periods separated by one year. Similarly, two screening blood pressure measurements were obtained from the subjects at each of two health examinations also taken 1 year apart. A total of 136 untreated subjects without cardiovascular complications (40 men and 96 women, 56 +/- 11.7 years, mean +/- SD) were analyzed in the study. The correlations between the first and second blood pressure measurements of the subjects were significantly higher for the home blood pressure measurements (systolic: r = 0.844 and diastolic: r = 0.830) than for the screening blood pressure measurements (systolic: r = 0.692 and diastolic: r = 0.570). The mean differences between the first and second home blood pressure (0.8 +/- 7.7 mm Hg for systolic BP and 0.9 +/- 5.5 mm Hg for diastolic BP) were significantly smaller than those for the screening blood pressure (-3.9 +/- 13.8 for systolic BP and -3.1 +/- 10.2 for diastolic BP) (P < .001 for both comparisons), suggesting that the reproducibility of home blood pressure over time is superior to that of screening blood pressure. Such reliable blood pressure measurements obtained at home have a clinical significance for the diagnosis and treatment of hypertension and as a tool for evaluating the efficacy of antihypertensive drugs. Home blood pressure measurements also may be more useful than screening blood pressure measurements in predicting future cardiovascular events.

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.