Kenichi Nagai

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.

Prognostic significance of blood pressure and heart rate variabilities: the Ohasama study

To investigate the association between cardiovascular mortality and short-term variabilities in blood pressure and heart rate, we performed a long-term prospective study of ambulatory blood pressure monitoring in Ohasama, Japan, starting in 1987. We obtained ambulatory blood pressure and heart rate in 1542 subjects ≥40 years of age. Blood pressure and heart rate variabilities were estimated as a standard deviation measured every 30 minutes by ambulatory monitoring. There were 67 cardiovascular deaths during the follow-up period (mean=8.5 years). The Cox proportional hazards model, adjusted for possible confounding factors, demonstrated a significant increase in cardiovascular mortality, with an increase in daytime systolic ambulatory blood pressure variability. A similar trend was observed in daytime diastolic and nighttime ambulatory blood pressures. Cardiovascular mortality rate increased linearly, with a decrease in daytime heart rate variability. Subjects in whom the daytime systolic ambulatory blood pressure variability was larger than third quintile and the daytime heart rate variability was lower than the mean−SD were at extremely high risk of cardiovascular mortality. The blood pressure and heart rate variabilities obtained every 30 minutes by ambulatory blood pressure monitoring were independent predictors for cardiovascular mortality in the general population.

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.

Prediction of stroke by ambulatory blood pressure monitoring versus screening blood pressure measurements in a general population : the Ohasama study

Objective To investigate the association between 24 h, daytime and night-time ambulatory blood pressures and first symptomatic stroke, to compare their predictive powers for stroke with that of casual (screening) blood pressure, and to compare the predictive power for stroke between daytime and night-time blood pressures, in a general population in Ohasama, Japan. Design A prospective cohort study. Subjects and methods We obtained ambulatory blood pressure on 1464 subjects aged ≥ 40 years without history of symptomatic stroke, then followed-up their stroke-free survival. There were 74 first symptomatic stroke during the follow-up period (mean = 6.4 years). The prognostic significance of blood pressure for stroke risk was examined by a Cox proportional hazards regression model adjusted for possible confounding factors. Results The non-parametric and parametric analysis indicated that 24-h, daytime and night-time ambulatory blood pressures were linearly related with stroke risk. The likelihood ratio analysis demonstrated that these ambulatory blood pressures were significantly better related to stroke risk than did screening blood pressure, and that daytime blood pressure better predicted stroke risk than did night-time blood pressure. Conclusions The present study which prospectively investigated the relation between ambulatory blood pressure and first symptomatic stroke risk in a general population demonstrated that (i) ambulatory blood pressure values were linearly related to stroke risk; (ii) ambulatory blood pressures had the stronger predictive power for stroke risk than did screening blood pressure; and (iii) daytime blood pressure better related to stroke risk than did night-time blood pressure.

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.

Reference Values for 24-Hour Ambulatory Blood Pressure Monitoring Based on a Prognostic Criterion The Ohasama Study

Although reference values for ambulatory blood pressure (ABP) monitoring have been investigated in several population studies, these values were derived from cross-sectional observations and were based merely on the statistical distribution of blood pressure values. Therefore, we conducted a prospective cohort study to identify reference values for 24-hour ABP in relation to prognosis. We obtained measurements of 24-hour ABP for 1542 subjects (565 men) aged 40 years and over in a general population of a rural Japanese community and then followed-up their survival status. There were 117 deaths during the follow-up period (mean, 6.2 years). The association between baseline 24-hour ABP values and mortality, examined by the Cox proportional hazards regression model adjusted for possible confounding factors, showed a better fit with a second-degree equation than with a first-degree equation. On the basis of the results of this analysis, we identified the following reference values as the optimal blood pressure ranges that predict the best prognosis: 120 to 133 mm Hg for systolic blood pressure and 65 to 78 mm Hg for diastolic blood pressure. 24-Hour ABP values >134/79 mm Hg and <119/64 mm Hg were related to increased risks for cardiovascular and noncardiovascular mortality, respectively. This is the first report to propose reference values for 24-hour ABP based on a prognostic criterion.

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

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.