Shigeru Hisamichi

Prognostic significance of the nocturnal decline in blood pressure in individuals with and without high 24-h blood pressure: the Ohasama study.

Objective To examine the relationship between the normal nocturnal decline in blood pressure and the risk of cardiovascular mortality in individuals with and without high 24-h blood pressure values. Methods We obtained 24-h ambulatory blood pressure readings from 1542 residents of Ohasama, Japan, who were aged 40 years or more and were representative of the Japanese general population. We then followed up their survival for a mean of 9.2 years. The relationship was analysed using a Cox proportional hazards model adjusted for possible confounding factors. Results There was a linear relationship between the nocturnal decline in blood pressure and cardiovascular mortality. On average, each 5% decrease in the decline in nocturnal systolic/diastolic blood pressure was associated with an approximately 20% greater risk of cardiovascular mortality. There were no significant interactions for the risk between 24-h systolic/diastolic blood pressure values and continuous values for the nocturnal decline in blood pressure (P for interaction > 0.6). Even when 24-h blood pressure values were within the normal range (< 135/80 mmHg, average 118/69 mmHg), diminished nocturnal decreases in systolic/diastolic blood pressure were associated with an increased risk of cardiovascular mortality. Conclusions This is the first study to demonstrate that a diminished nocturnal decline in blood pressure is a risk factor for cardiovascular mortality, independent of the overall blood pressure load during a 24-h period, in the general population.

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.

Green tea and the risk of gastric cancer in Japan

BACKGROUND Although laboratory experiments and case-control studies have suggested that the consumption of green tea provides protection against gastric cancer, few prospective studies have been performed. METHODS In January 1984, a total of 26,311 residents in three municipalities of Miyagi Prefecture, in northern Japan (11,902 men and 14,409 women 40 years of age or older), completed a self-administered questionnaire that included questions about the frequency of consumption of green tea. During 199,748 person-years of follow-up, through December 1992, we identified 419 cases of gastric cancer (in 296 men and 123 women). We used Cox regression to estimate the relative risk of gastric cancer according to the consumption of green tea. RESULTS Green-tea consumption was not associated with the risk of gastric cancer. After adjustment for sex, age, presence or absence of a history of peptic ulcer smoking status, alcohol consumption, other dietary elements, and type of health insurance, the relative risks associated with drinking one or two, three or four, and five or more cups of green tea per day, as compared with less than one cup per day, were 1.1 (95 percent confidence interval, 0.8 to 1.6), 1.0 (95 percent confidence interval, 0.7 to 1.4), and 1.2 (95 percent confidence interval, 0.9 to 1.6), respectively (P for trend=0.13). The results were similar after the 117 cases of gastric cancer that were diagnosed in the first three years of follow-up had been excluded, with respective relative risks of 1.2 (95 percent confidence interval, 0.8 to 1.8) 1.0 (95 percent confidence interval, 0.7 to 1.5), and 1.4 (95 percent confidence interval, 1.0 to 1.9) (P for trend=0.07). CONCLUSIONS In a population-based, prospective cohort study in Japan, we found no association between green-tea consumption and the risk of gastric cancer.

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.

The increase of female breast cancer incidence in Japan: Emergence of birth cohort effect

During recent decades, breast cancer incidence has been increasing in Japan. According to the latest reports from several cancer registries in Japan, the breast has become the leading cancer site in female cancer incidence. To analyze the trend of breast cancer incidence in detail, we summarized female breast cancer incidence in Miyagi Prefecture, Japan during 1959–1997, and evaluated the period and cohort effect on breast cancer incidence using the age‐period‐cohort model. Age‐specific and age‐standardized rates have increased over successive calendar periods. Around 1980, an accelerated increase in these incidence rates took place. A full model including age, period and cohort was best fitted to the trend of incidence. In the model, the effects of period and cohort were statistically significant. The nonlinear effect for cohort indicates an increasing trend, beginning with the cohort in 1888–1897, and the nonlinear effect for period showed a clear increase in risk with calendar period. Furthermore, the full model including a linear component showed a steadily upward trend in the cohort effect. Based on our own epidemiologic studies previously conducted in Miyagi Prefecture, and other published reports, the cohort effect is likely to be related to the change in prevalence of women with risk factors such as low parity and insufficient breastfeeding. We believe that the emergence of the cohort effect is an important finding, although the period effect may also persist. The significant cohort effect may give a caution for continuous increase of breast cancer incidence in Japan.