Association between job stress and depression among Japanese employees threatened by job loss in a comparison between two complementary job-stress models

OBJECTIVES

This study compared the separate effects produced by two complementary stress models--the job demand-control model and the effort-reward imbalance model--on depression among employees threatened by job loss.

METHODS

A cross-sectional analysis was conducted to examine these associations among 190 male and female employees who responded to a self-administered questionnaire in a small Japanese plant with economic hardship. The employees were engaged in 2 job types--direct assembly line and indirect supportive tasks--and the latter was threatened by job loss because of downsizing. Independent variables were measured by the Japanese versions of Karasek's demand-control questionnaire and Siegrist's effort-reward imbalance questionnaire. Depression was assessed by the Center for Epidemiologic Studies Depression Scale.

RESULTS

The employees with indirect supportive tasks (target for downsizing) were more likely to have depressive symptoms than direct assembly-line workers. Job strain, a combination of high demand and low control at work, was more frequent among the latter, while the combination of high effort and low reward was more frequent among the former. After adjustment for work environment factors, low control [odds ratio (OR) 4.7], effort reward imbalance (OR 4.1), and overcommitment (the person characteristic included in the effort-reward imbalance model) (OR 2.6) were independently related to depression. There is some indication that these effects were particularly strong in the subgroup suffering from potential job loss.

CONCLUSIONS

This study confirms that the 2 job stress models identify different aspects of stressful job conditions. Moreover, effort-reward imbalance and low control at work are both associated with symptoms of depression.

Distribution of serum C-reactive protein and its association with atherosclerotic risk factors in a Japanese population : Jichi Medical School Cohort Study

The distribution of serum C-reactive protein (CRP) levels and their association with age, sex, and atherosclerotic risk factors were studied in a large Japanese population between 1992 and 1995. The subjects consisted of 2,275 males and 3,832 females aged 30 years and over. CRP was measured by nephelometry. The distribution of CRP was highly skewed toward a lower level than that of previous studies and seemed to be a combination of two separate distribution curves. The increase in CRP with age was statistically significant, and males had higher CRP levels than did females. Males who were current smokers had higher CRP levels than did nonsmokers. Age, systolic blood pressure, diastolic blood pressure, triglycerides, fibrinogen, and body mass index were all positively associated with CRP in both sexes, while total cholesterol and blood glucose were positively related in females only. High density lipoprotein cholesterol was inversely related in both sexes. Multiple logistic regression analysis showed that sex, age, systolic pressure, high density lipoprotein cholesterol, triglycerides, fibrinogen, and body mass index were significant independent variables. In conclusion, the distribution of CRP among the Japanese was quite different from that among Westerners, although CRP levels correlated with other atherosclerotic risk factors, similar to those in Westerners.

Sleep duration and mortality in Japan: the Jichi Medical School Cohort Study

BACKGROUND

Although sleep is one of the most important health-related factors, relationship between sleep duration and mortality has not been fully discussed.

METHODS

Study subjects were 11,325 participants (4,419 males and 6,906 females) in the Jichi Medical School Cohort Study, a population-based prospective study. Baseline data were obtained by questionnaire and health checkups between April 1992 and July 1995 in 12 rural areas in Japan. Main outcome measures were all-cause and cause-specific mortality derived from death certificates up to December 31, 2001. Cox's proportional hazard models were applied to analyze the association of sleep duration with mortality.

RESULTS

A total of 495 deaths (289 males and 206 females) were observed during the average of 8.2-year follow-up period. After adjusting for age, systolic blood pressure, serum total cholesterol, body mass index, smoking habits, alcohol drinking habits, education, and marital status, the hazard ratios (95% confidence intervals) of all-cause mortality for individuals sleeping shorter than 6 hours and 9 hours or longer were 2.4 (1.3-4.2) and 1.1 (0.8-1.6) in males, and 0.7 (0.2-2.3) and 1.5 (1.0-2.4) in females, respectively, relative to those with 7-7.9 hours sleep.

CONCLUSION

Our data suggest that males with short sleep and females with long sleep were at an elevated risk of death.

Correlation between lipoprotein(a) and aortic valve sclerosis assessed by echocardiography (the JMS Cardiac Echo and Cohort Study)

An elevated serum level of lipoprotein(a) (Lp[a]) may be an independent risk factor for atherosclerotic disease, but the relation of Lp(a) to aortic valve (AV) sclerosis has not been determined. We measured serum concentrations of Lp(a) and investigated their relation to the presence of echocardiographic AV sclerosis in residents of a rural village in Japan. We measured serum Lp(a) levels in 347 men and 437 women aged 35 to 90 years (mean +/- SD: 62 +/- 11 years) who participated in mass screening examinations in Wara village, Gifu, Japan. AV sclerosis was assessed by long- and short-axis 2-dimensional echocardiographic views and continuous-wave Doppler echocardiography. AV sclerosis was graded as follows: 0 = normal AV; 1 = increased echo density; 2 = thickening or calcific deposits > or = 3 mm; and 3 = same as 2 with mildly restricted motion (pressure gradient < 16 mm Hg). Lp(a) levels ranged from < 1 mg/dl to 153 mg/dl. The 25th, 50th, and 75th percentile values were 7, 16, and 28 mg/dl, respectively. Lp(a) levels were significantly higher in women than in men (p < 0.01), and did not increase significantly with age. The prevalence of AV sclerosis (grades 2 and 3) increased significantly with age (p < 0.001). AV sclerosis was present in 65 (36.1%) of 180 subjects with Lp(a) levels > or = 30 mg/dl and in 77 (12.7%) of 604 subjects with Lp(a) levels < 30 mg/dl (p < 0.001). There were no significant differences in the prevalence of AV sclerosis in terms of sex, blood pressure, or levels of total cholesterol, high-density lipoprotein cholesterol, triglycerides, or blood sugar. We conclude that increased serum levels of Lp(a), as well as aging, are closely related to AV sclerosis.

Incidence of Kawasaki disease in Japan: the nationwide surveys of 1999-2002

BACKGROUND

The purpose of the present study was to describe the results of nationwide epidemiologic surveys of Kawasaki disease for the 4 year period 1999-2002.

METHODS

The design is a retrospective incidence survey. The patients reported in these two surveys are all new patients who were reported during the two study periods (1999-2000 and 2001-2002), although the data were collected retrospectively. A questionnaire was sent to all pediatric departments of hospitals with 100 beds or more throughout Japan, requesting data on patients with Kawasaki disease, such as sex, age, date of first hospital visit, recurrence, and cardiac lesions.

RESULTS

The total number of patients reported in the 4 year period 1999-2002 was 32 266 (18 604 male, 13 662 female), with an average annual incidence of 137.7 per 100 000 children younger than 5 years old. The male/female ratio was 1.30. The incidence peaked at 9-11 months of age, and the proportion of patients under 1 year of age was 26%. The monthly distribution had a high peak in January and a gradual increase in summer. Geographically, the high-incidence areas were limited to certain prefectures and moved from year to year. The cardiac lesions at acute stage and cardiac sequelae occurred more in children under 1 year and older than 4 years. Among the principal symptoms, fever persisting >or=5 days occurred most commonly, followed by conjunctival congestion, changes in lips and oral cavity, polymorphous exanthema, and changes of extremities. Cervical lymphadenopathy occurred less.

CONCLUSION

More than 32 000 patients with Kawasaki disease during the 4 year period 1999-2002 were reported to the nationwide incidence surveys. The number of patients is steadily increasing despite the decrease of children. The seasonal variation, geographical distribution, and age-specific distribution support the infection theory for the etiology of Kawasaki disease.

Association between job strain and prevalence of hypertension: a cross sectional analysis in a Japanese working population with a wide range of occupations: the Jichi Medical School cohort study

OBJECTIVES

To explore the association between the prevalence of hypertension in a Japanese working population and job strain (a combination of low control over work and high psychological demands), and to estimate this association in different sociodemographic strata.

METHODS

From a multicentre community based cohort study of Japanese people, sex specific cross sectional analyses were performed on 3187 men and 3400 women under 65 years of age, all of whom were actively engaged in various occupations throughout Japan. The baseline period was 1992-95 [corrected]. The association between job characteristics--measured with a Japanese version of the Karasek demand-control questionnaire--and the prevalence of hypertension defined by blood pressure and from clinical diagnoses were examined. Adjustments were made for possible confounders. The analyses were repeated for stratified categories of occupational class, educational attainment, and age group.

RESULTS

In men, the level of job strain (the ratio of psychological job demands to job control) correlated with the prevalence of hypertension. In a multiple logistic regression model, job strain was significantly related to hypertension (odds ratio 1.18; 95% confidence interval 1.05 to 1.32), after adjustment for age, employment (white collar v blue collar), marital status, family history of hypertension, cigarette smoking, alcohol intake, physical activity, and body mass index. The stratified analyses showed significant excess risks in the subordinate groups compared with managers, blue collar workers, less educated workers, and the older age groups. This association was not significant in women. Multiple linear regression analyses, with systolic and diastolic blood pressures as dependent variables, did not show any significant association.

CONCLUSIONS

The findings provided limited proof that job strain is related to hypertension in Japanese working men. Older men in a lower social class may be more vulnerable to the hypertensive effects of job strain.

Frequency of citrus fruit intake is associated with the incidence of cardiovascular disease: the Jichi Medical School cohort study

Background

It has been reported that fruit intake protects against cardiovascular disease (CVD). However, most of the relevant studies were conducted in Western countries, and only a few investigated Japanese populations. The present cohort study assessed the effect of citrus fruit intake on the incidence of CVD and its subtypes in a Japanese population.

Methods

A baseline examination consisting of physical and blood examinations and a self-administered questionnaire was conducted during the period from April 1992 through July 1995. Dietary habits were assessed using a food frequency questionnaire that was divided into 5 categories. Citrus fruit was examined separately due to its frequent consumption by the general Japanese population. Using the Cox proportional hazards model, data from 10 623 participants (4147 men, 6476 women) who had no history of CVD or carcinoma were analyzed to assess the association between frequency of citrus fruit intake and CVD incidence.

Results

Frequent intake of citrus fruit was associated with a lower incidence of CVD: the hazard ratio for almost daily intake versus infrequent intake of citrus fruit was 0.57 (95% confidence interval: 0.33–1.01, P for trend = 0.04) in men and 0.51 (0.29–0.88, P for trend = 0.02) in women. Frequent intake of citrus fruit was also associated with lower incidences of both all stroke and cerebral infarction, but not hemorrhagic stroke or myocardial infarction.

Conclusions

Frequent intake of citrus fruit may reduce the incidence of CVD, especially cerebral infarction, in men and women.

The Jichi Medical School (JMS) Cohort Study: design, baseline data and standardized mortality ratios

We have been conducting a cohort study titled the Jichi Medical School Cohort Study (The JMS Cohort Study) since 1992, which is aiming to clarify the risk factors of cardiovascular and cerebrovascular diseases in the Japanese. The baseline data were gathered from April 1992 through July 1995 in 12 rural districts using a legal mass screening system. The total samples were 12,490 males and females, and the overall response rate for the total population was 63%. The mean ages were 55.2 years for males and 55.3 years for females, respectively. Smoking rates were 50.5% and 5.5%, and drinking rates were 75.1% and 25.0% for males and females, respectively. We also examined the Standardized mortality ratios (SMRs) of the cohort subjects for 7.6 year follow-up period. The SMRs were 0.68 [95% confidence interval (CI): 0.59-0.78] for males and 0.73 (95% CI: 0.62-0.85) for females for the cohort subjects, whereas the SMRs were 1.00 (95% CI 0.97-1.04) for males and 1.06 (95% CI: 1.02-1.10) for females for all residents. In this article, we outlined the cohort study and showed general characteristics of the baseline data, and the SMRs of the subjects. We have been following the eligible subjects, and are preparing to show some prospective data regarding cardiovascular and cerebrovascular risks in the near future.

Sleep duration and incidence of cardiovascular events in a Japanese population: the Jichi Medical School cohort study

BACKGROUND

Although sleep is one of the most important health-related factors, the relationship between sleep duration and the incidence of cardiovascular events has not been fully described.

METHODS

The present study comprised the 11,367 study subjects (4413 men and 6954 women) of the Jichi Medical School Cohort Study, a population-based prospective study. Baseline data were obtained by questionnaire and health examinations between April 1992 and July 1995 in 12 rural areas in Japan, and the main outcome measures were the incidence of cardiovascular diseases (stroke and myocardial infarction [MI]). Cox proportional hazards models were used to analyze the association between sleep duration and the incidence of cardiovascular events.

RESULTS

A total of 481carciovascular events (255 men and 226 women) were observed during an average follow-up period of 10.7 years. After adjusting for age, systolic blood pressure, serum total cholesterol, body mass index, smoking habits, and alcohol drinking habits, the hazard ratios (95% confidence intervals) for the incidence of cardiovascular diseases for individuals sleeping less than 6 hours and 9 hours or longer were 2.14 (1.11-4.13) and 1.33 (0.93-1.92) in men, and 1.46 (0.70-3.04) and 1.28 (0.88-1.87) in women, respectively, relative to those who reported sleeping 7 to 7.9 hours per day.

CONCLUSIONS

Our data indicate that men who sleep less than 6 hours a day have a higher risk of cardiovascular events than those sleeping 7 to 7.9 hours.

Dietary patterns and levels of blood pressure and serum lipids in a Japanese population

BACKGROUND

Associations between dietary patterns and cardiovascular disease risk factors remain unclear. The objective of this study was to evaluate the association between dietary patterns derived from factor analysis and the levels of blood pressure and serum lipids in a Japanese population.

METHODS

We conducted a cross-sectional analysis among 6886 (in the analysis on blood pressure) and 7641 (in the analysis on serum lipids) Japanese subjects aged 40-69 years. Dietary patterns were identified from a food frequency questionnaire by factor analysis. Associations between dietary patterns and blood pressure and serum lipids were examined after taking potential confounders into account.

RESULTS

Three dietary patterns were identified: vegetable, meat, and Western. In men, the meat pattern was associated with higher total, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) cholesterol. The Western pattern was associated with higher total and LDL cholesterol. In women, the vegetable pattern was associated with lower systolic and diastolic blood pressure and pulse pressure, and higher HDL cholesterol. The meat pattern was associated with higher total and HDL cholesterol. The Western pattern was associated with higher total, HDL, and LDL cholesterol, and the least intake pattern of Western diet was associated with higher systolic and diastolic blood pressures.

CONCLUSIONS

Dietary patterns of a Japanese population were related to cardiovascular disease risk factors, especially in women.

Increasing incidence of Kawasaki disease in Japan: nationwide survey

BACKGROUND

The last nationwide survey of Kawasaki disease in Japan was conducted in 2003; the epidemiologic features of the disease in Japan since then are unknown.

METHODS

All the hospitals with a pediatric department and a bed capacity of > or =100, or hospitals having a bed capacity of <100 but specializing in pediatrics in Japan were asked to report (by mail) all patients with Kawasaki disease who visited the hospital due to the disease in 2003 and 2004.

RESULTS

Of the 2335 hospitals asked to participate, 1058 reported 19,138 patients with Kawasaki disease during the 2 year period 2003-2004. The annual incidence in 2004 reached 174.0 per 100,000 children under 5 years of age. The yearly number of patients and annual incidence increased significantly after the last nationwide epidemic of the disease in 1986. The number of patients was largest in January and lowest in October. The age-specific incidence was highest for those aged 9-11 months, and 88.9% of the patients were under 5 years of age. Of the reported patients, 2595 (13.6%) had cardiac lesions in the acute phase of the disease and 844 (4.4%) had cardiac sequelae 1 month after the onset of the disease.

CONCLUSION

The number of patients and the incidence of Kawasaki disease in Japan has increased year by year in the last two decades.

Low cholesterol is associated with mortality from stroke, heart disease, and cancer: the Jichi Medical School Cohort Study

Background

We investigated the relationship between low cholesterol and mortality and examined whether that relationship differs with respect to cause of death.

Methods

A community-based prospective cohort study was conducted in 12 rural areas in Japan. The study subjects were 12 334 healthy adults aged 40 to 69 years who underwent a mass screening examination. Serum total cholesterol was measured by an enzymatic method. The outcome was total mortality, by sex and cause of death. Information regarding cause of death was obtained from death certificates, and the average follow-up period was 11.9 years.

Results

As compared with a moderate cholesterol level (4.14–5.17 mmol/L), the age-adjusted hazard ratio (HR) of low cholesterol (<4.14 mmol/L) for mortality was 1.49 (95% confidence interval [CI]: 1.23–1.79) in men and 1.50 (1.10–2.04) in women. High cholesterol (≥6.21 mmol/L) was not a risk factor. This association was unchanged in analyses that excluded deaths due to liver disease, which yielded age-adjusted HRs of 1.38 (95% CI, 1.13–1.67) in men and 1.49 (1.09–2.04) in women. The multivariate-adjusted HRs and 95% CIs of the lowest cholesterol group for hemorrhagic stroke, heart failure (excluding myocardial infarction), and cancer mortality significantly higher than those of the moderate cholesterol group, for each cause of death.

Conclusions

Low cholesterol was related to high mortality even after excluding deaths due to liver disease from the analysis. High cholesterol was not a risk factor for mortality.

Association between job characteristics and health behaviors in Japanese rural workers

Associations between job characteristics defined by the Karasek's job demand-control model and health behaviors were investigated in a cross-sectional analysis of 6,759 Japanese rural workers. High psychological demands were associated with heavy smoking, exaggerated prevalence of alcohol drinking, and high work-related physical activity. Low job control was associated with lower consumption of vegetables, a smaller quantity number of cigarettes smoked, and a low level of work-related physical activity. Job strain, a combined measure obtained from the ratio of demands to control, was associated with lower vegetable consumption, low prevalence of smoking, and high prevalence of current alcohol drinking. Stratified analyses by occupations and gender provided some but not all of the explanations for the unexpected findings. The results indicate a possible association between psychosocial job characteristics and health behaviors. A few unexpected findings prevent complete support to one of the hypothetical pathways that the job characteristics lead to cardiovascular disease through behaviors.

Low control at work and the risk of suicide in Japanese men: a prospective cohort study

BACKGROUND

Although adverse psychosocial job characteristics are suspected predictors of suicide death, prospective studies based on established stress instruments are limited.

METHODS

In a multicenter community-based Japanese cohort study, we prospectively investigated the association between psychosocial job characteristics and the risk of death from suicide among male workers. Baseline examination was conducted from 1992 to 1995 to determine the socioeconomic, behavioural and biological variables in addition to the psychosocial job characteristics of 3,125 male workers aged 65 and under and free from major illness. Low job control and high job demands were measured as adverse psychosocial job characteristics according to a job demand-control model questionnaire. Suicide deaths were identified using the Cause-of-Death Register.

RESULTS

During the 9-year follow-up, 14 suicides were identified. The suicide death rate was 48.1 per 100,000 person years. Multivariate analysis revealed a more than fourfold increase in the risk of suicide among men with low control at work (relative risk: 4.10; 95% confidence interval: 1.31-12.83) compared with counterpart men after adjustment for age, marital status, educational attainment, occupation, smoking status, alcohol consumption, total cholesterol level, and study area. Job demands were not associated with risk of death from suicide.

CONCLUSIONS

By using a job demand-control model questionnaire, low control at work was revealed as a predictor of suicide death among Japanese male workers. The finding implies that job redesign aimed at increased worker control could be a worthwhile strategy in preventing, or at least reducing, the risk of suicide death.

Prospective study on occupational stress and risk of stroke

BACKGROUND

No prospective studies have examined the association between occupational stress according to the job demand-control model and the risk of stroke in Asian populations.

METHODS

We conducted a multicenter community-based prospective study of 6553 Japanese male and female workers. Occupational stress was evaluated using a Japanese version of the job demand-control model questionnaire. We used the Cox proportional hazards model to evaluate the association between occupational stress and stroke.

RESULTS

During a mean follow-up of 11 years, we identified 147 incident strokes. Multivariable analysis revealed a more than 2-fold increase in the risk of total stroke among men with job strain (combination of high job demand and low job control) (hazard ratio, 2.73; 95% confidence interval, 1.17-6.38) compared with counterpart men with low strain (combination of low job demand and high job control) after adjustment for age, educational attainment, occupation, smoking status, alcohol consumption, physical activity, and study area. Additional adjustments for biologic risk factors attenuated the hazard ratio, but there continued to be statistical significance (hazard ratio, 2.53; 95% confidence interval, 1.08-5.94). In women, no statistically significant differences were found for any stroke incidence among the job characteristic categories.

CONCLUSION

Occupational stress related to job strain was associated with incident strokes among Japanese men.

Incidence of total stroke, stroke subtypes, and myocardial infarction in the Japanese population: the JMS Cohort Study

Background

Previous reports indicated that the incidence rate of stroke was higher in Japan than in Western countries, but the converse was true in the case of myocardial infarction (MI). However, few population-based studies on the incidence rates of stroke and MI have been conducted in Japan.

Methods

The Jichi Medical School (JMS) Cohort Study is a multicenter population-based cohort study that was conducted in 12 districts in Japan. Baseline data were collected between April 1992 and July 1995. We examined samples from 4,869 men and 7,519 women, whose mean ages were 55.2 and 55.3 years, respectively. The incidence of stroke, stroke subtypes, and MI were monitored.

Results

The mean follow-up duration was 10.7 years. A total of 229 strokes and 64 MIs occurred in men, and 221 strokes and 28 MIs occurred in women. The age-adjusted incidence rates (per 100,000 person-years) of stroke were 332 and 221 and those of MI were 84 and 31 in men and women, respectively. In the case of both sexes, the incidence rates of stroke and MI were the highest in the group of subjects aged > 70 years.

Conclusion

We reported current data on the incidence rates of stroke and MI in Japan. The incidence rate of stroke remains high, considerably higher than that of MI, in both men and women. The incidence rates of both stroke and MI were higher in men than in women.

Cornell product left ventricular hypertrophy in electrocardiogram and the risk of stroke in a general population

Left ventricular hypertrophy (LVH), assessed by ECG, is associated with an increased risk for cardiovascular events among hypertensive subjects. We evaluated the risks of LVH in a Japanese general population including normotensive and prehypertensive subjects. We measured ECG and blood pressure in 10 755 subjects at baseline. The Cornell product (CP) and Sokolow-Lyon (SL) voltage were calculated as markers of LVH (CP >or=2440 mm x ms and SL voltage >or=38 mm). Follow-up was performed for 10 years, and the incidence of stroke and myocardial infarction was evaluated. The prevalence of CP-LVH was 2.7% for normotensives, 5.2% for prehypertensives, and 11.0% for hypertensives, and the prevalence of SL-LVH was 5.0%, 8.2%, and 15.2%, respectively. In all of the subjects, CP-LVH and SL-LVH were both predictors of stroke (CP-LVH: hazard risk: 1.62, 95% CI: 1.19 to 2.20, P=0.002; SL-LVH: hazard risk: 1.29, 95% CI: 0.98 to 1.71, P=0.07) after adjustment for confounding factors but were not predictors of myocardial infarction. The adjusted hazard ratio of CP-LVH predicting stroke was especially high in the normotensives (hazard risk: 7.53; 95% CI: 3.39 to 16.77). In the normotensives, diabetes mellitus and hyperlipidemia were significant determinants of CP-LVH but not of SL-LVH. In all of the hypertensive subgroups (normotensives, prehypertensives, and hypertensives), the c-statistic for the equation predicting stroke increased when CP-LVH was added to the model but not when SL-LVH was added. In conclusion, both CP-LVH and SL-LVH are risk factors for stroke in the Japanese general population. CP-LVH is related to glucose abnormality, and its predictive value for stroke is seen even in normotensives and prehypertensives.

Prevalence and determinants of prehypertension in a Japanese general population: the Jichi Medical School Cohort Study

It has been reported that subjects with prehypertension (pre-HT) (systolic blood pressure [SBP] 120-139 mmHg and/or diastolic blood pressure [DBP] 80-89 mmHg) have an increased risk of cardiovascular disease (CVD). We evaluated the prevalence and determinants of pre-HT in a Japanese general population. We enrolled 4,706 males and 7,342 females aged 18 to 90 years whose BPs were measured at baseline. The subjects' BPs were classified as follows: normotension (NT: SPB/DBP < 120/80 mmHg), pre-HT (120/80-139/89 mmHg), and hypertension (HT: > or = 140/90 mmHg or treated hypertension). The prevalence of pre-HT was 34.8% (males), and 31.8% (females). Body mass index (BMI) of more than 23.0 kg/m2 was the strongest determinant of pre-HT (Males--BMI: 23.0-24.9 kg/m2, odds ratio [OR] = 1.47, 95% confidence interval [CI] = 1.21-1.79; BMI: 25.0-26.9 kg/m2, OR = 2.20, 95% CI =1.68-2.87; BMI: 27.0-29.9 kg/m2, OR = 2.75, 95% CI = 1.80-4.19; BMI: > or = 30.0 kg/m2, OR = 3.39, 95% CI = 1.21-9.46. Females--BMI: 23.0-24.9 kg/m2, OR = 1.67, 95% CI = 1.42-1.95; BMI: 25.0-26.9 kg/m2, OR = 1.79, 95% CI = 1.46-2.19; BMI: 27.0-29.9 kg/m2, OR = 3.65, 95% CI = 2.73-4.89; BMI: > or = 30.0 kg/m2, OR = 4.23, 95% CI = 2.33-7.70). The other determinants of pre-HT were hyperlipidemia (Males: OR = 1.25; Females: OR = 1.43), and aging (by 10 years; Males: OR = 1.12; Females: OR = 1.48). Determinants of pre-HT in females were impaired glucose tolerance (OR = 1.41, 95% CI = 1.03-1.94), diabetes (OR = 2.01, 95% CI = 1.16-3.47) and a family history of HT in both parents (OR = 1.90, 95% CI = 1.38-2.62), whereas in males the only other predictor was alcohol drinking (OR = 1.45, 95% CI = 1.23-1.70). In conclusion, even subjects with a mild increase of BMI (23.0-24.9 kg/m2) had an increased risk of pre-HT in a Japanese population, and the level of BMI associated with pre-HT was lower than that in Western countries. Additionally, there were gender differences in the determinants of pre-HT.

Metabolic Syndrome and C-Reactive Protein in the General Population JMS Cohort Study

BACKGROUND

In recent years some studies have shown that metabolic syndrome (MS) is associated with inflammation, indicated by high-sensitivity C-reactive protein (hsCRP), but there have been few population-based studies, especially in Japan.

METHODS AND RESULTS

The study subjects were 2,191 men and women examined between 1992 and 1995 with the necessary data to ascertain MS as part of the Jichi Medical School Cohort Study. CRP was measured by nephelometry. There were 109 subjects defined as having MS (5.0%), and the proportion of MS cases was higher in men (9.4%) than in women (1.8%). Geometric mean and median CRP in the MS group was higher than that in the non-MS (geometric mean; p<0.001, median: 0.312 mg/L in MS and 0.122 mg/L). Proportion of MS increased with CRP, after the subjects were divided by tertile of CRP (odds ratio, 95% confidence interval 1st tertile as a reference; 2nd tertile: 2.9, 1.5-5.9, 3rd tertile: 5.7, 3.1-11.1).

CONCLUSION

Inflammation, measured by the concentration of hsCRP, was elevated in cases of MS in the general Japanese population. Longitudinal data should be examined in the future.

Lipoprotein(a) levels in the Japanese population: influence of age and sex, and relation to atherosclerotic risk factors. The Jichi Medical School Cohort Study

The authors studied the distribution of lipoprotein(a) (Lp(a)) levels with stratification for age and sex, as well as the relation between Lp(a) and atherosclerotic risk factors in a large Japanese population between 1992 and 1993. The subjects were 1,235 males and 1,762 females over 30 years old. Lp(a) was measured by an enzyme-linked immunosorbent assay. Lp(a) levels were higher in females than in males. The increase in Lp(a) with age was statistically significant, and the proportion of subjects with Lp(a) levels > 30 mg/dl also increased with age. In the obese subjects (body mass index (BMI) (kg/m2) > 26), Lp(a) levels were lower than in the non-obese subjects (BMI < or = 26) (p < 0.01 in males; p < 0.05 in females). Male alcohol drinkers had lower Lp(a) levels than nondrinkers (p < 0.05). Age, low density lipoprotein subtracting Lp(a) cholesterol [Lp(a) x 0.3], and fibrinogen level were all positively correlated with Lp(a) in both sexes. Alcohol consumption (g/day) and triglycerides were inversely correlated with Lp(a) in males, while total cholesterol subtracting Lp(a) cholesterol [Lp(a) x 0.3], high density lipoprotein, and factor VII were positively correlated in females. Multiple logistic regression analysis showed that triglycerides in males and BMI and fibrinogen in females were significant independent variables. The authors conclude that Lp(a) level is affected by various factors, such as alcohol drinking, BMI, sex, and age, and is not only correlated with lipid levels but also with hemostatic factors such as fibrinogen and factor VII.

Age at menopause and mortality in Japan: the Jichi Medical School Cohort Study

BACKGROUND

Although several studies have reported increased mortality risk with early menopause, there were no studies examining the relationship between age at menopause and mortality in Japan. The goal of this analysis is to investigate the relationship between age at menopause and all-cause mortality among the Japanese.

METHODS

Study subjects were 4,683 postmenopausal females in the Jichi Medical School Cohort Study, a population-based prospective study. Baseline data were obtained by questionnaire and health checkups between April 1992 and July 1995 in 12 rural areas in Japan. Main outcome measures were all-cause mortality derived from death certificates up to December 31, 2002. Cox's proportional hazard models were used to analyze the association of age at menopause with mortality.

RESULTS

A total of 215 deaths were observed during the average of 9.2 year follow-up period. After adjusting for age, systolic blood pressure, serum total cholesterol level, serum high density lipoprotein cholesterol level, history of diabetes mellitus, body mass index, smoking habits, alcohol drinking habits, marital status, study area, and types of menopause, the hazard ratios (95% confidence intervals) of all-cause mortality were 2.10 (1.07-4.11), 0.68 (0.36-1.26), 0.94 (0.68-1.30), and 1.17 (0.63-2.20) for females with a menopause at ages younger than 40 years, 40-44, 50-54, and 55 or older, respectively, relative to those with menopause at age 45-49 years.

CONCLUSIONS

Our data suggest that menopause aged younger than 40 years increases the risk of death from all causes among the Japanese.

Impact of occupational stress on stroke across occupational classes and genders

The aims of the present study were to analyze the association between incident stroke, occupational class and stress and to examine whether the association is found in both men and women in a prospective study of Japanese male and female workers. A total of 3190 male and 3363 female Japanese community-dwelling workers aged 65 or under with no history of cardiovascular disease were followed. Occupational stress was evaluated using a demand-control questionnaire. The impact on stroke was examined in stratified analyses of occupational classes. We identified 147 incident strokes (91 in men and 56 in women) during the 11-year follow-up period. Men with high strain jobs (combination of high job demand and low job control) were nearly three times more likely to suffer from a stroke than men with low strain jobs (combination of low job demand and high job control). Among male workers in low occupational classes (blue-collar and non-managerial work), job strain was associated with a higher risk of stroke. In contrast, there was no association between job strain and incident stroke among male workers in high occupational classes (white-collar and managerial work). No statistically significant differences were found for stroke incidence among the job characteristic categories in all the female participants. However, significant, over five-fold excess risks were found among white-collar and managerial female workers exposed to high job strain, compared with their counterparts with low strain jobs. Our study of Japanese workers provided supportive evidence for vulnerability to occupational stress among lower occupational class workers in males but not in females.

A common mutation in methylenetetrahydrofolate reductase gene among the Japanese population

Hyperhomocysteinemia has been reported as an independent risk factor for atherosclerotic cerebrovascular and coronary heart diseases. 5, 10-Methylenetetrahydrofolate reductase (MTHFR) is one of the enzymes responsible for hyperhomocysteinemia. The C to T transition of the MTHFR gene at nucleotide position 677 results in decreasing the enzymatic activity and increasing the plasma homocysteine level. We studied the distribution of the MTHFR gene mutation among the Japanese population. The subjects were 129 Japanese males (aged 40-59 years). The allele frequency of the mutation was 0.38. The frequencies of the three genotypes were as follows: +/+, 11%; +/-, 54%; -/-, 35% (+ and-indicate the presence and absence of the mutation, respectively). We also studied the frequency of the MTHFR gene mutation in the middle-aged Japanese males with hypertension to investigate the possibility that this mutation is related to essential hypertension. The normotensive and hypertensive subjects were identical in the distribution of the mutated allele and the frequencies of the three genotypes. Furthermore, the prevalence of hypertension in each genotype group was same, although the mean diastolic pressure of the group with homozygous mutation was significantly higher than that of other groups (p < 0.05). Therefore, we concluded that there was no significant relationship between the MTHFR gene mutation and hypertensive subjects studied in this study.

Five-year intra-individual variability in C-reactive protein levels in a Japanese population-based study: the Jichi Medical School Cohort Study at Yamato, 1993-1998

C-reactive protein (CRP) is an acute-phase reactant that is related to future cardiovascular events. However, little is known about the long-term intra-individual stability of CRP in community residents. The 5-year intra-individual correlation of CRP levels was examined in the Jichi Medical School Cohort Study in Japan. CRP measurements were obtained in 1993 and in 1998 from 388 presumptively healthy individuals aged 30-69 years at baseline. The Pearson's correlation coefficient of CRP between baseline and follow-up measurements was 0.43 (95% confidence interval (CI): 0.34-0.51). Additional analyses by sex and smoking status at baseline revealed similar coefficients. The correlation coefficient of CRP was lower than that of other classical risk factors, such as body-mass index (BMI), blood pressure, and total and high-density lipoprotein (HDL) cholesterol. A subgroup of individuals with higher levels of CRP at both baseline and follow-up measurements had higher BMI, hemoglobin Alc, and plasma fibrinogen, and lower levels of HDL-cholesterol than others, even after adjusting for age, sex, and smoking status in a multiple logistic model. In conclusion, the stability of CRP levels was statistically significant in a long-term population-based study. A subgroup with higher levels of CRP who had an aggregation of cardiovascular risk factors was identified by the 2 measurements.