A prospective cohort study on National Health Insurance beneficiaries in Ohsaki, Miyagi Prefecture, Japan: study design, profiles of the subjects and medical cost during the first year

Gamma-glutamyltransferase and cancer incidence: the Ohsaki cohort study

Background

Although experimental studies have shown that gamma-glutamyltransferase (GGT) has a role in tumor progression, epidemiologic evidence for a relationship between GGT and cancer incidence is limited. The present study investigated the association between GGT and cancer incidence and assessed the role of alcohol consumption in this association.

Methods

We examined a cohort of 15 031 Japanese adults aged 40 to 79 years who attended a health checkup in 1995 and were free of cancer at that time. GGT was measured using the Szasz method. The participants were then followed from 1 January 1996 until 31 December 2005, and cancer incidence was recorded by using the Miyagi Regional Cancer Registry. Hazard ratios (HRs) and 95% confidence intervals (CIs) were computed for each quartile of GGT and compared. The lowest quartile (GGT <13.0 IU/ml) was used as the reference category.

Results

We documented 1505 cancers. Among participants in the highest quartile (GGT ≥31.0 IU/ml), the multivariate HR for any cancer was 1.28 (95% CI, 1.08–1.53; P for trend, <0.001), the HR for colorectal cancer was significantly greater than unity, and the HRs for esophageal, pancreatic, and breast cancers were greater than unity but not significantly so. This positive trend was observed only in current drinkers.

Conclusions

Our findings suggest that there is a positive relationship between GGT and cancer incidence only for alcohol-related cancers in current drinkers and that the positive association of GGT with cancer incidence largely reflects alcohol consumption.

[Lifetime medical expenditures of smokers and nonsmokers]

OBJECTIVES

The aim of this study was to examine which of the two groups have higher lifetime medical expenditures; male smokers or male nonsmokers. We conducted this investigation using a Japanese single cohort database to calculate long-term medical expenditures and 95% confidence intervals.

METHODS

We first constructed life tables for male smokers and male nonsmokers from the age of 40 years after analyzing their mortality rates. Next, we calculated the average annual medical expenditures of each of the two groups, categorized into survivors and deceased. Finally, we calculated long-term medical expenditures and performed sensitivity analyses.

RESULTS

The results showed that although smokers had generally higher annual medical expenditures than nonsmokers, the former's lifetime medical expenditure was slightly lower than the latter's because of a shorter life expectancy that resulted from a higher mortality rate. Sensitivity analyses did not reverse the order of the two lifetime medical expenditures.

CONCLUSIONS

In conclusion, although smoking may not result in an increase in lifetime medical expenditures, it is associated with diseases, decreased life expectancy, lower quality of life (QOL), and generally higher annual medical expenditures. It is crucial to promote further tobacco control strategically by maximizing the use of available data.

Impact of obesity, overweight and underweight on life expectancy and lifetime medical expenditures: the Ohsaki Cohort Study

OBJECTIVES

People who are obese have higher demands for medical care than those of the normal weight people. However, in view of their shorter life expectancy, it is unclear whether obese people have higher lifetime medical expenditure. We examined the association between body mass index, life expectancy and lifetime medical expenditure.

DESIGN

Prospective cohort study using individual data from the Ohsaki Cohort Study.

SETTING

Miyagi Prefecture, northeastern Japan.

PARTICIPANTS

The 41 965 participants aged 40-79 years.

PRIMARY AND SECONDARY OUTCOME MEASURES

The life expectancy and lifetime medical expenditure aged from 40 years.

RESULTS

In spite of their shorter life expectancy, obese participants might require higher medical expenditure than normal weight participants. In men aged 40 years, multiadjusted life expectancy for those who were obese participants was 41.4 years (95% CI 38.28 to 44.70), which was 1.7 years non-significantly shorter than that for normal weight participants (p=0.3184). Multiadjusted lifetime medical expenditure for obese participants was £112 858.9 (94 954.1-131 840.9), being 14.7% non-significantly higher than that for normal weight participants (p=0.1141). In women aged 40 years, multiadjusted life expectancy for those who were obese participants was 49.2 years (46.14-52.59), which was 3.1 years non-significantly shorter than for normal weight participants (p=0.0724), and multiadjusted lifetime medical expenditure was £137 765.9 (123 672.9-152 970.2), being 21.6% significantly higher (p=0.0005).

CONCLUSIONS

According to the point estimate, lifetime medical expenditure might appear to be higher for obese participants, despite their short life expectancy. With weight control, more people would enjoy their longevity with lower demands for medical care.

Body mass index and mortality from all causes and major causes in Japanese: results of a pooled analysis of 7 large-scale cohort studies

BACKGROUND

We pooled data from 7 ongoing cohorts in Japan involving 353 422 adults (162 092 men and 191 330 women) to quantify the effect of body mass index (BMI) on total and cause-specific (cancer, heart disease, and cerebrovascular disease) mortality and identify optimal BMI ranges for middle-aged and elderly Japanese.

METHODS

During a mean follow-up of 12.5 years, 41 260 deaths occurred. The Cox proportional hazards model was used to estimate hazard ratios (HRs) for each BMI category, after controlling for age, area of residence, smoking, drinking, history of hypertension, diabetes, and physical activity in each study. A random-effects model was used to obtain summary measures.

RESULTS

A reverse-J pattern was seen for all-cause and cancer mortality (elevated risk only for high BMI in women) and a U- or J-shaped association was seen for heart disease and cerebrovascular disease mortality. For total mortality, as compared with a BMI of 23 to 25, the HR was 1.78 for 14 to 19, 1.27 for 19 to 21, 1.11 for 21 to 23, and 1.36 for 30 to 40 in men, and 1.61 for 14 to 19, 1.17 for 19 to 21, 1.08 for 27 to 30, and 1.37 for 30 to 40 in women. High BMI (≥27) accounted for 0.9% and 1.5% of total mortality in men and women, respectively.

CONCLUSIONS

The lowest risk of total mortality and mortality from major causes of disease was observed for a BMI of 21 to 27 kg/m(2) in middle-aged and elderly Japanese.

Attributable fractions of risk factors for cardiovascular diseases

Background

Cardiovascular disease (CVD) is a leading cause of death in Japan. To reduce the threat of CVD, it is important to identify its major risk factors. The population attributable fraction (PAF) is calculated from the prevalence and relative risk of risk factors and can be used to estimate the burden of these factors with respect to CVD. We analyzed the findings from several prospective studies to determine the PAFs of CVD.

Methods

PAF was calculated as pd × (multiadjusted relative risk − 1)/multiadjusted relative risk, where pd is the proportion of patients exposed to that risk factor category, according to data from the Ohsaki Cohort Study, EPOCH-JAPAN, NIPPON DATA80, Miyagi Cohort Study, CARDIA Study, and ARIC Study.

Results

Nonoptimal blood pressure explained 47% and 26% of CVD mortality in middle-aged and elderly Japanese, respectively. Cigarette smoking explained 34% of all-cause mortality in middle-aged men. The combination of hypertension and cigarette smoking explained 57% and 44% of CVD mortality in younger men and women, respectively. Furthermore, the presence of at least 1 nonoptimal risk factor explained most CVD deaths and all-cause deaths.

Conclusions

Established CVD risk factors, especially high blood pressure and cigarette smoking, explained a large proportion of CVD mortality and all-cause mortality. Prevention, early detection, and treatment of these conventional risk factors are required to reduce mortality risk.

Impact of walking on life expectancy and lifetime medical expenditure: the Ohsaki Cohort Study

OBJECTIVE

People who spend a longer time walking have lower demands for medical care. However, in view of their longer life expectancy, it is unclear whether their lifetime medical expenditure increases or decreases. The present study examined the association between time spent walking, life expectancy and lifetime medical expenditure.

METHOD

The authors followed up 27,738 participants aged 40-79 years and prospectively collected data on their medical expenditure and survival covering a 13-year-period. Participants were classified into those walking <1 and ≥1 h per day. The authors constructed life tables and estimated the life expectancy and lifetime medical expenditure from 40 years of age using estimate of multiadjusted mortality and medical expenditure using a Poisson regression model and linear regression model, respectively.

RESULTS

Participants who walked ≥1 h per day have a longer life expectancy from 40 years of age than participants who walked <1 h per day. The multiadjusted life expectancy for those who walked ≥1 h per day was 44.81 years, significantly lower by 1.38 years in men (p=0.0073) in men and 57.78 years in women, non-significantly lower by 1.16 years in women (p=0.2351). In addition to their longer life expectancy, participants who walked ≥1 h per day required a lower lifetime medical expenditure from 40 years of age than participants who walked <1 h per day. The multiadjusted lifetime medical expenditure for those who walked ≥1 h per day was £99 423.6, significantly lower by 7.6% in men (p=0.0048) and £128 161.2, non-significantly lower by 2.7% in women (p=0.2559).

DISCUSSION

Increased longevity resulting from a healthier lifestyle does not necessarily translate into an increased amount of medical expenditure throughout life. Encouraging people to walk may extend life expectancy and decrease lifetime medical expenditure, especially for men.

History of cholelithiasis and the risk of prostate cancer: the Ohsaki Cohort Study

An association between cholelithiasis and prostate cancer has been reported sporadically in previous case-control and experimental studies, suggesting that cholesterol may play a promotional role in prostate cancer development and progression. However, this relationship remains poorly understood, and population evidence based on a strict study design is needed. The authors examined the history of cholelithiasis and the development of prostate cancer in the Ohsaki cohort followed from 1995 to 2003, in which 230 new cases of prostate cancer were ascertained among 22,458 Japanese men. Baseline information, including history of cholelithiasis, was collected using a self-administered questionnaire. The Cox proportional hazards regression model was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). The results showed that patients with a history of cholelithiasis had a higher risk of prostate cancer with a multivariate adjusted HR of 1.72 (95% CI: 1.12-2.66), and especially for advanced prostate cancer, the corresponding value was 2.29 (95% CI: 1.21-4.35). The associations were robust after adjustment for different potential confounders. This population-based prospective cohort study indicates that a history of cholelithiasis is associated with an increased incidence of prostate cancer.

Participation in health check-ups and mortality using propensity score matched cohort analyses

OBJECTIVE

All Japanese aged ≥40 years are eligible for free annual health check-ups including blood pressure and cholesterol measurements. It is well known that health check-up screenees are more likely to have healthy lifestyles and better health conditions than non-screenees. Therefore, controlling these factors is required to investigate whether screenees have a lower mortality risk than non-screenees independent of their lifestyles or health conditions.

METHODS

We followed 48,775 Japanese National Health Insurance beneficiaries aged 40-79 years since 1994 for 11 years. We used Cox proportional hazard models adjusted for possible confounding factors. We also performed propensity for use of the health check-up matched cohort analyses.

RESULTS

Compared to non-screenees, multiple-adjusted hazard ratios (95% confidence intervals) for all-cause and cardiovascular disease mortality among screenees were 0.74 (0.62-0.88) and 0.65 (0.44-0.95) for men and 0.69 (0.52-0.91) and 0.61 (0.36-1.04) for women, respectively. These relations were also observed when we used propensity matched cohort analyses.

CONCLUSION

This is the first study to show that mortality rates are lower among screenees than non-screenees in Japanese health check-ups when propensity matched cohort analyses were used for adjusting confounding factors. Further prospective studies, including randomized controlled trials, are required to confirm whether screening lowers mortality.

Citrus consumption and cancer incidence: the Ohsaki cohort study

Basic research and case-control studies have suggested that citrus consumption may protect against cancer. However, the protective effect has been observed from few prospective studies. This study investigated the association of citrus consumption with cancer incidence among 42,470 Japanese adults in the Ohsaki National Health Insurance Cohort, which covered an age range of 40-79 years, and was followed up from 1995 to 2003 for all-cancer and individual cancer incidence. Citrus consumption was assessed using a self-administered questionnaire. The Cox proportional hazard model was applied to estimate relative risks (RRs) and 95% CIs. During the 323,204 person-years of follow-up, 3,398 cases were identified totally. Citrus consumption, especially daily consumption, was correlated with reduced all-cancer incidence, the RRs were 0.89 (95% CI = 0.80-0.98) for total participants, 0.86 (0.76-0.98) for males and 0.93 (0.79-1.09) for females, as well as multiple cancers at individual sites, especially pancreatic (RR = 0.62, 95% CI = 0.38-1.00) and prostate cancer (RR = 0.63, 95% CI = 0.41-0.97). Joint effect analysis showed a reduced risk of overall cancer existed only for subjects who consumed >or=1 cup green tea/day (RR = 0.83, 95% CI = 0.73-0.93) as well as for males (RR = 0.83, 95% CI = 0.71-0.97) or females (RR = 0.82, 95% CI = 0.68-0.99). These findings suggest that citrus consumption is associated with reduced all-cancer incidence, especially for subjects having simultaneously high green tea consumption. Further work on the specific citrus constituents is warranted, and clinical trials are ultimately necessary to confirm the protective effect.

Effect of age on the association between body mass index and all-cause mortality: the Ohsaki cohort study

Background

To clarify the effect of age on the association between body mass index (BMI) and all-cause mortality.

Methods

We followed 43 972 Japanese participants aged 40 to 79 years for 12 years. Cox proportional hazards regression analysis was used to estimate hazard ratios (HRs), using the following BMI categories: <18.5 (underweight), 18.5–20.9, 21.0–22.9, 23.0–24.9 (reference), 25.0–27.4, 27.5–29.9, and ≥30.0 kg/m² (obese). Analyses were stratified by age group: middle-aged (40–64 years) vs elderly (65–79 years).

Results

We observed a significantly increased risk of mortality in underweight elderly men: the multivariate HR was 1.26 (0.92–1.73) in middle-aged men and 1.49 (1.26–1.76) in elderly men. In addition, we observed a significantly increased risk of mortality in obese middle-aged men: the multivariate HR was 1.71 (1.17–2.50) in middle-aged men and 1.25 (0.87–1.80) in elderly men. In women, there was an increased risk of mortality irrespective of age group in the underweight: the multivariate HR was 1.46 (0.96–2.22) in middle-aged women and 1.47 (1.19–1.82) in elderly women. There was no excess risk of mortality with age in obese women: the multivariate HR was 1.47 (0.94–2.27) in middle-aged women and 1.26 (0.95–1.68) in elderly women.

Conclusions

As compared with the reference category, obesity was associated with a high mortality risk in middle-aged men, whereas underweight, rather than obesity, was associated with a high mortality risk in elderly men. In women, obesity was associated with a high mortality risk during middle age; underweight was associated with a high mortality risk irrespective of age. The mortality risk due to underweight and obesity may be related to sex and age.

The Ohsaki Cohort 2006 Study: design of study and profile of participants at baseline

BACKGROUND

Large-scale cohort studies conducted in Japan do not always include psychosocial factors as exposures. In addition, such studies sometimes fail to satisfactorily evaluate disability status as an outcome.

METHODS

This prospective cohort study comprised 49 603 (22 438 men and 27 165 women) community-dwelling adults aged 40 years or older who were included in the Residential Registry for Ohsaki City, Miyagi Prefecture, in northeastern Japan. The baseline survey, which included psychosocial factors, was conducted in December 2006. Follow-up of death, immigration, cause of death, cancer incidence, and long-term care insurance certification was started on 1 January 2007.

RESULTS

The response rate was 64.2%. In general, lifestyle-related conditions in the study population were similar to those of the general Japanese population; however, the proportion of male current smokers was higher in the cohort. The association between age and the proportion of those reporting psychological distress showed a clear U-shaped curve, with a nadir at age 60 to 69 years in both men and women, although more women were affected by such distress than men. The proportion of those who reported a lack of social support was highest among those aged 40 to 49 years. Most men and women surveyed did not participate in community activities. Among participants aged 65 years or older, 10.9% of participants were certified beneficiaries of the long-term care insurance system at baseline.

CONCLUSIONS

The Ohsaki Cohort 2006 Study is a novel population-based prospective cohort study that focuses on psychosocial factors and long-term care insurance certification.

Factors influencing participation rate in a baseline survey of a genetic cohort in Japan

BACKGROUND

Although many studies have examined factors that influence the response to postal questionnaires, few have addressed baseline recruitment for cohort studies involving genetic analyses. The aim of this study was to describe the method used for a baseline survey, the Japan Multi-institutional Collaborative Cohort Study (J-MICC Study), in Saga Prefecture, and to examine the factors that might influence the recruitment of participants in such studies.

METHODS

The Saga J-MICC Study is an ongoing population-based prospective cohort study of the genetic and environmental interactions associated with lifestyle-related disease. From 2005 through 2007, a total of 61 447 residents between the ages of 40 and 69 were invited by mail to participate in this study. The survey date and time were arranged by telephone.

RESULTS

Among that population, 31 002 (50.5%) responded and 12 078 (19.7%) agreed to participate. A completed questionnaire and blood pressure and anthropometric data were collected from all participants; blood, DNA specimens, and accelerometer measures were obtained from the great majority of them. Female sex and older age were associated with a higher participation rate. In addition, the convenience of the survey location and the sending of a reminder significantly improved the participation rate (odds ratio, 1.3).

CONCLUSIONS

Our findings suggest that making the survey location as convenient as possible and sending a reminder can both substantially improve participation rate in population-based studies.

Difference in lifetime medical expenditures between male smokers and non-smokers

OBJECTIVES

It is controversial whether smokers have higher lifetime medical expenditures than non-smokers, because smokers have high annual medical expenditures but comparatively short lives. We examined differences in lifetime medical expenditures between them.

METHODS

We constructed life tables for male smokers and non-smokers from 40 years of age. We calculated average annual medical expenditures of them categorized by survivors and deceased, which were used to examine differences in lifetime medical expenditures between them and perform sensitivity analyses.

RESULTS

Smokers had a higher mortality rate, shorter life expectancy, and generally higher annual medical expenditures than non-smokers. We also observed tendencies for smokers to have higher inpatient expenditures, but non-smokers to have higher outpatient expenditures. Although non-smokers had lower long-term cumulative medical expenditures between 64 and 81 years of age, their lifetime medical expenditures were higher by a minimal amount. Sensitivity analyses did not change this result.

CONCLUSIONS

Smoking may not cause increases in lifetime medical expenditures because smokers had lower lifetime medical expenditures than non-smokers. However, it was clear that smokers, especially survivors, often had higher annual medical expenditures than non-smokers. The importance of tobacco control is still relevant.

Green tea consumption and the risk of liver cancer in Japan: the Ohsaki Cohort study

OBJECTIVES

To investigate the association between green tea consumption and liver cancer incidence.

METHODS

We prospectively followed 41,761 Japanese adults aged 40-79 years, without a history of cancer at the baseline or any missing data for green tea consumption frequency. Cox proportional hazards models were used to calculate hazard ratios (HR) with 95% confidence intervals (CI), adjusted for age, alcohol drinking, smoking, the consumption of coffee, vegetables, dairy products, fruit, fish, and soybean.

RESULTS

Over 9 years of follow-up, among 325,947 accrued person-years, the total incidence of liver cancer was 247 cases. We found that green tea consumption was inversely associated with the incidence of liver cancer. In men, the multivariate-adjusted HRs (95% CIs) for liver cancer incidence with different green tea consumption categories were 1.00 (reference) for <1 cup/day, 0.83 (0.53-1.30) for 1-2 cups/day, 1.11 (0.73-1.68) for 3-4 cups/day, and 0.63 (0.41-0.98) for >/=5 cups/day (p for trend = 0.11). The corresponding data among women were 1.00 (reference), 0.68 (0.35-1.31), 0.79 (0.44-1.44), 0.50 (0.27-0.90) (p for trend = 0.04).

CONCLUSIONS

Green tea consumption is associated with a reduced risk of liver cancer incidence.

Green tea consumption and hematologic malignancies in Japan: the Ohsaki study

Several biologic studies have reported that green tea constituents have antitumor effects on hematologic malignancies. However, the effects in humans are uncertain. The authors used data from the Ohsaki National Health Insurance Cohort Study in Japan to evaluate the association between green tea consumption and the risk of hematologic malignancies. Study participants were 41,761 Japanese adults aged 40-79 years without a history of cancer at baseline who answered a food frequency questionnaire survey in 1994. During 9 years of follow-up beginning in 1995, the authors documented 157 hematologic malignancies, including 119 cases of lymphoid neoplasms and 36 cases of myeloid neoplasms. Hazard ratios were calculated by using the Cox proportional hazards regression model. Risk of hematologic malignancies was inversely associated with green tea consumption. The multivariate-adjusted hazard ratio of hematologic malignancies for 5 cups/day or more compared with less than 1 cup/day of green tea was 0.58 (95% confidence interval: 0.37, 0.89). The corresponding risk estimate was 0.52 (95% confidence interval: 0.31, 0.87) for lymphoid neoplasms and 0.76 (95% confidence interval: 0.32, 1.78) for myeloid neoplasms. This inverse association was consistent across sex and body mass index strata. In conclusion, green tea consumption was associated with a lower risk of hematologic malignancies.

Green tea and death from pneumonia in Japan: the Ohsaki cohort study

BACKGROUND

Experimental and animal studies have shown the activities of catechins, the main constituents of green tea, against infectious agents. No data are available on the association between green tea consumption and the risk of pneumonia in humans.

OBJECTIVE

We examined the association between green tea consumption and death from pneumonia in humans.

DESIGN

We conducted a population-based cohort study, with follow-up from 1995 to 2006. The participants were National Health Insurance beneficiaries in Japan (19,079 men and 21,493 women aged 40-79 y). We excluded participants for whom data on green tea consumption frequency were missing or who had reported a history of cancer, myocardial infarction, stroke, and extreme daily energy intake at baseline. We used Cox proportional hazards regression analysis to calculate hazard ratios (HRs) and their 95% CIs for death from pneumonia according to green tea consumption.

RESULTS

Over 12 y of follow-up, we documented 406 deaths from pneumonia. In women, the multivariate HRs of death from pneumonia that were associated with different frequencies of green tea consumption were 1.00 (reference) for <1 cup/d, 0.59 (95% CI: 0.36, 0.98) for 1-2 cups/d, 0.55 (95% CI: 0.33, 0.91) for 3-4 cups/d, and 0.53 (95% CI: 0.33, 0.83) for > or =5 cups/d, respectively (P for trend: 0.008). In men, no significant association was observed.

CONCLUSION

Green tea consumption was associated with a lower risk of death from pneumonia in Japanese women.

Fish consumption and the risk of colorectal cancer: the Ohsaki Cohort Study

BACKGROUND

Evidence from laboratory and animal studies suggests that high fish consumption may reduce the risk of colorectal cancer, but the results of studies in humans have been inconsistent. The objective of this study was to prospectively examine the association between fish consumption and the risk of colorectal cancer incidence in Japan, where fish is widely consumed.

METHODS

We analysed data from 39 498 men and women registered in the Ohsaki National Health Insurance Cohort Study who were 40-79 years old and free of cancer at the baseline. Fish consumption was assessed at the baseline using a self-administered food frequency questionnaire.

RESULTS

During 9 years of follow-up, we identified 566 incident cases of colorectal cancer (379 men and 187 women). The hazard ratios and 95% confidence intervals (CIs) for colorectal cancer incidence in the highest quartile of fish consumption compared with the lowest quartile were 1.07 (95% CIs; 0.78-1.46, P-trend=0.43) for men, and 0.96 (95% CIs; 0.61-1.53, P-trend=0.69) for women.

CONCLUSION

The results of this prospective cohort study revealed no association between fish consumption and the risk of colorectal cancer.

Pain and risk of completed suicide in Japanese men: a population-based cohort study in Japan (Ohsaki Cohort Study)

Unrelieved pain is a major factor that influences suicide risk among terminally ill patients, but little is known about the relationship between pain and the risk of completed suicide in the general population. We prospectively examined the association between self-reports of pain and subsequent risk of completed suicide in 26,481 men aged 40 to 79 years from the Ohsaki National Health Insurance Cohort study, a population-based, prospective cohort study initiated in 1994. On the basis of a five-item questionnaire on pain, individuals were classified as having no pain, very mild pain, mild pain, or moderate or severe pain. Completed suicide cases were documented from 1995 to 2001. During 131,027 person-years, 64 completed suicides were documented. After adjustment for covariates, the risk for completed suicide was significantly higher in the subjects with more pain. Multivariate hazard ratios (95% confidence intervals) relative to the subjects who had no pain were 1.36 (0.67-2.75), 2.11 (1.02-4.33), and 2.93 (1.34-6.42) in the subjects who had very mild pain, mild pain, and moderate or severe pain, respectively (P for trend=0.004). Stratified analysis showed that the positive association between pain and suicide risk was robust in the subjects with good health, low stress, adequate sleep, good physical activity, and no history of chronic diseases. Our results suggest that pain is associated with an increased risk of completed suicide among Japanese men. The association was consistently observed among apparently healthy subjects.

Attributable risk fraction of prehypertension on cardiovascular disease mortality in the Japanese population: the Ohsaki Study

BACKGROUND

Although relative risk of prehypertension (pre-HT) on cardiovascular disease (CVD) mortality is modest, prevalence of pre-HT is large, that is, population attributable fraction (PAF) of pre-HT on CVD mortality might be large. However, no studies have reported the fraction.

METHODS

We followed 12,928 Japanese National Health Insurance (NHI) beneficiaries aged 40-79 years without a history of CVD. On the basis of their blood pressure (BP), the participants were categorized as normal BP, pre-HT, and hypertension (HT) (Seventh Report of the Joint National Committee criteria). Multivariate-adjusted Cox proportional hazards model was used to estimate the hazard ratio (HR) of the BP status vs. CVD mortality.

RESULTS

During 12-years of follow-up, 321 participants died of CVD. As positive relation between BP category and CVD mortality was steeper in middle-aged (40-64 years) than that in elderly (65-79 years), we separately calculated PAF on CVD mortality among middle-aged and elderly. HR (95% confidence interval) for cardiovascular mortality for pre-HT and HT, respectively, was 1.31 (0.59-2.94) and 2.98 (1.39-6.41) in middle-aged, and 1.03 (0.62-1.70) and 1.65 (1.02-2.64) in elderly. Non-normal BP, i.e., pre-HT and HT, accounted for 47 and 26% of the CVD deaths among the middle-aged and elderly participants, respectively. Although the PAF of pre-HT was larger in the middle-aged participants (7%) than that in the elderly ones (0%), neither fraction was considered large.

CONCLUSION

The PAF on CVD mortality in pre-HT was not large compared with that in HT.

Sleep duration and the risk of breast cancer: the Ohsaki Cohort Study

In a prospective study of 23 995 Japanese women, short sleep duration was associated with higher risk of breast cancer (143 cases), compared with women who slept 7 h per day, the multivariate hazard ratio of those who slept ⩽6 h per day was 1.62 (95% confidence interval: 1.05–2.50; P for trend=0.03).

Green tea consumption and lung cancer risk: the Ohsaki study

We examined the risk of lung cancer in relation to green tea consumption in a population-based cohort study in Japan among 41 440 men and women, aged 40–79 years, who completed a questionnaire in 1994 regarding green tea consumption and other health-related lifestyle factors. During the follow-up period of 7 years (from 1995 to 2001), 302 cases of lung cancer were identified, and the Cox proportional hazards regression model was used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs). The multivariable-adjusted HRs of lung cancer incidence for green tea consumption of 1 or 2, 3 or 4, and 5 or more cups/day as compared to less than 1 cup/day were 1.14 (95% CI: 0.80–1.62), 1.18 (95% CI: 0.83–1.66), and 1.17 (95% CI: 0.85–1.61), respectively (P for trend=0.48). This cohort study has found no evidence that green tea consumption is associated with lung cancer.

The relation between green tea consumption and cardiovascular disease as evidenced by epidemiological studies

Although substantial evidence from in vitro and animal studies indicates that green tea preparations inhibit cardiovascular disease processes, the possible protective role of green tea consumption against this disease in humans remains unclear. We conducted a population-based prospective cohort study (the Ohsaki Study) to examine the association between green tea consumption and mortality from cardiovascular disease (CVD), cancer, and all causes with 40,530 persons in Miyagi prefecture, in northern Japan. Previously published work has shown that green tea consumption was inversely associated with mortality from CVD and all causes. The inverse association of mortality from CVD was more pronounced in women (P = 0.08 for interaction with sex). In women, the multivariate hazard ratios (95% confidence intervals) of CVD mortality across increasing green tea consumption categories were 1.00, 0.84 (0.63-1.12), 0.69 (0.52-0.93), 0.69 (0.53-0.90) (P for trend = 0.004). Within CVD mortality, the stronger inverse association was observed for stroke mortality. Because our observational study has found the inverse association, I report here the results of a review of epidemiological evidence from randomized controlled trials (RCT) of the association between green tea or green tea extracts and CVD risk profiles. More than half of the RCT have demonstrated the beneficial effects of green tea on CVD risk profiles. These results from RCT suggest a plausible mechanism for the beneficial effects of green tea and provide substantial support for our observations.

Sense of life worth living (ikigai) and mortality in Japan: Ohsaki Study

OBJECTIVE

To investigate the association between the sense of "life worth living (ikigai)" and the cause-specific mortality risk. The psychological factors play important roles in morbidity and mortality risks. However, the association between the negative psychological factors and the risk of mortality is inconclusive.

METHODS

The Ohsaki Study, a prospective cohort study, was initiated on 43,391 Japanese adults. To assess if the subjects found a sense of ikigai, they were asked the question, "Do you have ikigai in your life?" We used Cox regression analysis to calculate the hazard ratio of the all-cause and cause-specific mortality according to the sense of ikigai categories.

RESULTS

Over 7 years' follow-up, 3048 of the subjects died. The risk of all-cause mortality was significantly higher among the subjects who did not find a sense of ikigai as compared with that in the subjects who found a sense of ikigai; the multivariate adjusted hazard ratio (95% confidence interval) was 1.5 (1.3-1.7). As for the cause-specific mortality, subjects who did not find a sense of ikigai were significantly associated with an increased risk of cardiovascular disease (1.6; 1.3-2.0) and external cause mortality (1.9; 1.1-3.3), but not of the cancer mortality (1.3; 1.0-1.6).

CONCLUSIONS

In this prospective cohort study, subjects who did not find a sense of ikigai were associated with an increased risk of all-cause mortality. The increase in mortality risk was attributable to cardiovascular disease and external causes, but not cancer.

Body mass index and cardiovascular disease mortality in Japan: the Ohsaki Study

OBJECTIVE

Although there is a clear positive association between obesity and the incidence and severity of cardiovascular disease, the association between underweight and cardiovascular disease is unclear. The objective of this study was to examine the relation between body mass index (BMI) and cardiovascular disease in Japan, where the proportion of the population that is underweight is relatively high.

METHOD

A total of 43,916 Japanese adults (21,003 men and 22,913 women) aged 40 to 79 years who had no history of cancer, ischemic heart disease (IHD), or stroke participated in the baseline survey in 1994. Hazard ratios (HR) and their 95% confidence intervals (CIs) for death due to total cardiovascular disease, all strokes, ischemic stroke, hemorrhagic stroke, and IHD were calculated according to BMI by using Cox's proportional hazards regression models. The 22.5-24.9 kg/m(2) BMI category was used as the reference category in all analyses.

RESULTS

There were U-shaped associations between BMI and total cardiovascular disease, all stroke, hemorrhagic stroke, and IHD mortality, and a J-shaped association between BMI and ischemic stroke mortality. Participants with a BMI <18.5 kg/m(2) had a significantly increased risk of total cardiovascular disease, all stroke, hemorrhagic stroke, and IHD mortality, and the multivariate HR (95% CI) was 1.62 (1.19-2.19), 1.50 (1.02-2.21), 2.11 (1.07-4.17), 1.83 (1.11-3.01), respectively.

CONCLUSION

Underweight was substantially associated with hemorrhagic stroke and IHD mortality in Japan, while obesity was associated with increased risk of total cardiovascular disease mortality and mortality from individual cardiovascular diseases.

Sleep duration and the risk of prostate cancer: the Ohsaki Cohort Study

In a prospective study of prostate cancer incidence (127 cases), among 22 320 Japanese men, sleep duration was associated with lower risk; the multivariate hazard ratio of men who slept ⩾9 h per day compared with those who slept less was 0.48 (95% confidence interval: 0.29–0.79, P for trend=0.02).

Alcohol consumption and suicide mortality among Japanese men: the Ohsaki Study

The risk of suicide is well known to be increased among heavy alcohol drinkers. However, whether the risk is increased or decreased among light drinkers is still under debate. We investigated this association in a population-based sample of men in Japan. The Ohsaki Study was a population-based, prospective cohort study among Japanese adults aged from 40 to 79 years. Between October and December, 1994, 22,804 men in Miyagi Prefecture, Japan, completed a questionnaire on various health-related lifestyles, including alcohol drinking. During the subsequent 7 years follow-up, 73 participants committed suicide. We used the Cox proportional hazards regression model to estimate the hazard ratio (HR) for suicide mortality according to the quantity of alcohol consumed daily, with adjustment for potential confounders. There was a statistically significant positive and linear association between the amount of alcohol consumed and the risk of suicide: the multivariate HRs in reference to nondrinkers (95% confidence interval) were 1.2 (0.5-2.7), 1.5 (0.7-3.4), and 2.4 (1.2-4.6) in current drinkers who consumed </=22.7g, 22.8g-45.5g, and >/=45.6g of alcohol per day, respectively (P-trend=.016). Even after the early death cases were excluded, a significant linear association was observed between alcohol consumption and the risk of suicide, with the risk of suicide also being nonsignificantly higher among the light drinkers than among nondrinkers (multivariate HR=1.7). This prospective cohort study indicated a positive linear association between alcohol consumption and the risk of suicide, and the suicide risk among the light drinkers was not decreased as compared with that in nondrinkers.

The joint impact of cardiovascular risk factors upon medical costs

OBJECTIVE

The joint impact of obesity, hypertension, and hyperglycemia upon medical costs is not well known. Our objective was to evaluate the joint impact of these cardiovascular risk factors upon medical costs in the rural Japanese population.

METHODS

The data were derived from a 6-year prospective observation of National Health Insurance beneficiaries in rural Japan. Data on blood chemistry tests, blood pressure, weight, and height were obtained from an annual health check-up provided by the local municipalities in 1995. We prospectively collected data on medical costs over a 6-year period for 12,340 subjects (5306 men and 7034 women) without prior histories of cardiovascular disease or cancer.

RESULTS

Mean medical costs for individuals being overweight/obese, hypertensive, and hyperglycemic were 91.0% higher than those for individuals without any of these three cardiovascular risk factors. In this cohort, 17.2% of total medical costs were attributable to these three risk factors.

CONCLUSION

Overweight/obesity, hypertension, and hyperglycemia could have a large impact on health care resources in rural Japan.

Dietary patterns and cardiovascular disease mortality in Japan: a prospective cohort study

BACKGROUND

Although ecological observations suggest that the Japanese diet may reduce the risk of cardiovascular disease (CVD), the impact of a Japanese dietary pattern upon mortality due to CVD is unclear.

METHODS

We prospectively assessed the association between dietary patterns among the Japanese and CVD mortality. Dietary information was collected from 40 547 Japanese men and women aged 40-79 years without a history of diabetes, stroke, myocardial infarction or cancer at the baseline in 1994.

RESULTS

During 7 years of follow-up, 801 participants died of CVD. Factor analysis (principal component) based on a validated food frequency questionnaire identified three dietary patterns: (i) a Japanese dietary pattern highly correlated with soybean products, fish, seaweeds, vegetables, fruits and green tea, (ii) an 'animal food' dietary pattern and (iii) a high-dairy, high-fruit-and-vegetable, low-alcohol (DFA) dietary pattern. The Japanese dietary pattern was related to high sodium intake and high prevalence of hypertension. After adjustment for potential confounders, the Japanese dietary pattern score was associated with a lower risk of CVD mortality (hazard ratio of the highest quartile vs the lowest, 0.73; 95% confidence interval: 0.59-0.90; P for trend = 0.003). The 'animal food' dietary pattern was associated with an increased risk of CVD, but the DFA dietary pattern was not.

CONCLUSION

The Japanese dietary pattern was associated with a decreased risk of CVD mortality, despite its relation to sodium intake and hypertension.

Impact of hypertension on medical economics: A 10-year follow-up study of national health insurance in Shiga, Japan

Hypertension and related cardiovascular diseases may lead to an increase in medical costs for patients. We attempted to clarify the relationship between hypertension and long-term medical costs by a cohort study utilizing existing data as well as baseline blood pressures and medical costs over a 10-year period. The participants included 4191 Japanese National Health Insurance beneficiaries aged 40-69 years, living in one area, who were not taking anti-hypertensive medication and did not have a history of major cardiovascular disease. They were classified into four categories according to their blood pressure. We evaluated the mean medical costs per month, cumulative hospitalization, and all-cause mortality for each blood pressure category. Hypertension-related medical costs attributable to hypertensive individuals, as compared to normotensive individuals, were estimated. There was a positively graded correlation between blood pressure and personal total medical costs, especially for men. The odds ratio for cumulative hospitalization and hazard ratio for all-cause mortality in severe hypertensive men were also higher than those in normotensive men. However, the hypertension-related medical costs for mild to moderate hypertensives were higher than those for severe hypertensives. The hypertension-related medical costs for all hypertensives accounted for 23.7% of the total medical costs for the Japanese population. In conclusion, high blood pressure was a useful predictor for excess medical costs; moreover, concomitant hypertension, regardless of the grade, increased the medical costs of Japanese National Health Insurance beneficiaries.

Modifiable factors for the length of life with disability before death: mortality retrospective study in Japan

BACKGROUND

Past studies have measured and described the length of life with disability before death, but there has been no study of the relationship between modifiable lifestyle factors and duration of disability.

OBJECTIVE

To examine whether there are modifiable factors influencing the length of life with disability before death.

METHODS

The study was designed as a retrospective observation of the deceased who had earlier been enrolled in a prospective cohort study. During the follow-up period (1996-1999), we documented 781 deaths among those who were 70-79 years of age at the baseline survey in 1994 (n=10,216). In 2000, we interviewed family members of the deceased about the duration of the subjects' disability before death (n=655).

RESULTS

The median duration of disability before death was approximately 6 months. Both higher Body Mass Index (BMI) and shorter time spent walking were significantly associated with an increased risk of long-term disability (more than 6 months). The odds ratios of long-term disability were 1.3 in those with BMI 20-25 and 2.1 in those with BMI>25, compared with BMI<20. The odds ratios of long-term disability were 1.3 in those walking for 0.5-0.9 h/day and 1.7 in those walking for <0.5 h/day, compared with those walking for >1.0 h/day. These relationships were unchanged after stratification for causes of death.

CONCLUSION

Weight control and walking in later life may shorten the length of life with disability before death.

Impact of alcohol consumption upon medical care utilization and costs in men: 4-year observation of National Health Insurance beneficiaries in Japan

AIMS

The purpose of the present study was to examine the association between alcohol consumption and in-patient and out-patient care utilization and its costs, respectively.

DESIGN AND PARTICIPANTS

The present data were derived from a 4-year prospective observation of National Health Insurance beneficiaries in rural Japan. A total of 17 497 men aged 40-79 years were analysed, after excluding subjects who at the baseline reported having had at least one of four chronic diseases: stroke, myocardial infarction, liver disease and cancer. Alcohol intake was classified into five groups, not including ex-drinkers: life-long abstainers and ethanol intakes of 1-149 g/week, 150-299 g/week, 300-449 g/week, and > or = 450 g/week.

FINDINGS

The hospital days and in-patient care cost showed a U-shaped relationship with alcohol consumption. In-patient cost was highest for those consuming more than 450 g/week [ pound 74.96, 95% confidence interval (CI): 54.39, 95.52] and for life-long abstainers ( pound 69.16, 95% CI: 62.08, 77.83), and lowest for those consuming 150-299 g/week ( pound 51.69, 95% CI: 45.33, 58.04). In-patient use by age specific analysis also showed a U-shape at all ages, and was lowest for those consuming 1-149 g/week in youngest age group. In contrast, the number of physician visits and out-patient cost showed an inverse linear relationships with alcohol consumption.

CONCLUSIONS

This study suggests that in-patient use shows a U-shaped curve and out-patient use shows an inverse linear relationship to alcohol consumption.

Joint impact of health risks on health care charges: 7-year follow-up of National Health Insurance beneficiaries in Japan (the Ohsaki Study)

BACKGROUND

The objective of this study was to examine the joint impact of modifiable health-risk factors such as smoking, obesity, and physical inactivity on direct health care charges.

METHOD

We conducted a population-based prospective cohort study, with follow-up from 1995 to 2001. The participants were Japanese National Health Insurance (NHI) beneficiaries (26,110 men and women aged 40-79 years).

RESULTS

'No risk' group defined as never-smoking, body mass index (BMI) 20.0-24.9 kg/m(2), and walking for >/=1 h/day had mean health care charges of 171.6 dollars after adjustment for potential confounders. Compared with this group, the presence of smoking (SM; ever-smoking) alone, obesity alone (OB; BMI >/=25.0 kg/m(2)), or physical inactivity (PI; walking for <1 h/day) alone were associated with a 8.3%, 7.1%, or 8.0% increase in health care charges, respectively. The combinations of the risks of SM and OB, SM and PI, OB and PI, and SM and OB and PI were associated with a 11.7%, 31.4%, 16.4%, and 42.6% increase in charges, respectively.

CONCLUSION

Interventions to improve modifiable health-risk factors may be a cost-effective approach for reducing health care charges as well as improving people's health.

Reliability and Validity of the Multidimensional Health Locus of Control Scale in Japan: Relationship with Demographic Factors and Health-Related Behavior

We assessed the reliability and validity of the Multidimensional Health Locus of Control Scale (MHLC scale) in a rural Japanese community. The study subjects were 2388 men and 2454 women aged 40-79 years, who completed a questionnaire regarding socio-demographics, health-related behavior, such as smoking and drinking, and the MHLC. The Cronbach alpha of the MHLC scale, which is an indicator of the internal consistency of the scale, was within the range 0.62-0.76. Elderly subjects, women, and subjects with fewer years of education showed more "external" belief, which is generally consistent with previous reports from overseas. Subjects with adverse health behavior, such as smoking and excess drinking, also had more "external" belief. These results indicate that the MHLC scale has sufficient reliability and validity among the Japanese population. Use of the MHLC scale should help to provide a better understanding of health belief among Japanese, and development of health education programs to prevent lifestyle-related disease.

Impact of walking upon medical care expenditure in Japan: the Ohsaki Cohort Study

BACKGROUND

Physical activity is expected to reduce medical costs by lowering the risk for a variety of chronic diseases. However, little is known about the actual magnitude of medical cost saved by physical activity. We attempted to quantify the association between time spent walking and medical care costs, based on a 4-year prospective observation of National Health Insurance (NHI) beneficiaries in rural Japan.

METHODS

In 27 431 Japanese men and women, aged 40-79 years, who had no functional limitation or conditions interfering with physical activity at the baseline survey in 1994, we ascertained all hospitalizations, outpatient visits, and the costs through computerized linkage with NHI claims history files between January 1995 and December 1998.

RESULTS

Medical costs significantly reduced with longer time spent walking. Per capita medical cost was pound 111.80 per month (95% CI: 109.3, 114.2) in those who walked for < or =30 minutes/day, pound 108.10 (95% CI: 105.7, 110.5) in those who walked for 30 minutes-1 hour, and pound 97.30 (95% CI: 95.5, 99.0) in those who walked for > or =1 hour, after multivariate adjustment of potential confounders.

CONCLUSIONS

This prospective study in Japan indicated that time spent walking was significantly associated with lower medical costs.

Validation of a food-frequency questionnaire for cohort studies in rural Japan

OBJECTIVES

To examine the validity and reproducibility of a self-administered food-frequency questionnaire (FFQ) used for two cohort studies in Japan.

DESIGN

Cross-sectional study.

SETTING

Two rural towns in the Miyagi Prefecture, in north-eastern Japan.

SUBJECTS

Fifty-five men and 58 women.

RESULTS

A 40-item FFQ was administered twice, 1 year apart. In the mean time, four 3-day diet records (DRs) were collected in four seasons within the year. We calculated daily consumption of total energy and 15 nutrients, 40 food items and nine food groups from the FFQs and the DRs. We computed Spearman correlation coefficients between the FFQs and the DRs. With adjustment for age, total energy and deattenuation for measurement error with the DRs, the correlation coefficients for nutrient intakes ranged from 0.25 to 0.58 in men and from 0.30 to 0.69 in women, with median of 0.43 and 0.43, respectively. Median (range) of the correlation coefficients was 0.35 (-0.30 to 0.72) in men and 0.34 (-0.06 to 0.75) in women for food items and 0.60 (-0.10 to 0.76) and 0.51 (0.28-0.70) for food groups, respectively. Median (range) of the correlation coefficients for the two FFQs administered 1 year apart was 0.49 (0.31-0.71) in men and 0.50 (0.40-0.64) in women for nutrients, 0.43 (0.14-0.76) and 0.45 (0.06-0.74) respectively for food items, and 0.50 (0.30-0.70) and 0.57 (0.39-0.66) respectively for food groups. Relatively higher agreement percentages for intakes of nutrients and food groups with high validity were obtained together with lower complete disagreement percentages.

CONCLUSIONS

The FFQ has a high reproducibility and a reasonably good validity, and is useful in assessing the usual intakes of nutrients, foods and food groups among a rural Japanese population.

Practical aspects of designing and conducting pharmacoeconomic studies in Japan

The advent of simultaneous global clinical trials and drug registration strategies has increased the demand for global pharmacoeconomic strategies. Outcomes researchers in pharmaceutical companies are faced with the challenge of assessing at a strategic level what pharmacoeconomic data are most useful in Japan and when, and then deciding at a tactical level what type of study designs are feasible. This paper is written mainly for the benefit of researchers working outside of Japan in the pharmaceutical/medical device industry or academia who are interested in conducting research in Japan. We reviewed the existing pharmacoeconomic literature in Japan, and found that the number of studies per year has been steadily increasing. The majority of studies have been cost-effectiveness and cost-consequence analyses. Typical data sources available in Japan are somewhat limited compared with other Western countries. However, charge data can be easily accessed through the national uniform reimbursement fee system and these data are particularly relevant for pharmaceutical pricing negotiations with the Ministry of Health, Labor and Welfare (MHLW). The present use of pharmacoeconomic data by pharmaceutical companies is mainly for pricing negotiations but recent reforms make certain types of data useful for marketing strategies too. The demand for pharmacoeconomic data may increase because of upcoming MHLW pharmaceutical pricing and/or recent health insurance system reforms. Economic evaluation of medical technologies in Japan, though lagging behind North America, Australia and Europe, has the potential to rapidly gather momentum as increasing cost-escalation worries contribute to a growing interest in pharmacoeconomic data.

Medical care expenditure associated with body mass index in Japan: the Ohsaki Study

OBJECTIVE

To examine the impact of body mass index (BMI) upon medical care use and its costs in Japan.

DESIGN

A population-based prospective cohort study from 1995 to 1998.

SUBJECTS

A cohort of 41 967 Japanese adults aged 40-79 y. Subjects who died during the first year of follow-up, or who at baseline reported having had cancer, myocardial infarction, stroke or kidney disease were excluded.

MEASUREMENTS

Medical care use and its costs, actual charges, by linkage with the National Health Insurance claim history files after adjustment of smoking, drinking and physical functioning status.

RESULTS

There was a U-shaped association between BMI and total medical costs. The nadir of the curve was found at a BMI of 21.0-22.9 kg/m(2). Relative to the nadir, total costs were 9.8% greater among those with BMIs of 25.0-29.9 (rate ratio, 1.10; 95% confidence interval (CI), 1.03-1.17), and 22.3% greater among those with BMIs of 30.0 or higher (rate ratio, 1.22; 95% CI, 1.08-1.37). Estimated excess direct costs attributable to overweight (BMI of 25.0-29.9 kg/m(2)) and obesity (BMI of 30.0 kg/m(2) or higher) represent 3.2% of total health expenditure in the present study, which is within the range reported in Western countries (0.7-6.8%).

CONCLUSION

Our prospective data demonstrate that the impact of overweight and obesity upon medical care costs in Japan is as large as in Western countries, despite the much lower mean BMI in Japanese populations.

Food frequency questionnaire and a screening test

We assessed the accuracy of a 141-item food frequency questionnaire as a screening test to detect high or low consumption of nutrients associated with cancer. Fifty-five men and 58 women participating in two population-based cohort studies in Miyagi, Japan, provided four three-day diet records over a one-year period and subsequently completed the questionnaire twice with a one-year interval. Pearson correlation coefficients between 17 nutrients measured by the diet records and the first questionnaire ranged from 0.24 to 0.85 (median 0.43), and those between the two questionnaires ranged from 0.47 to 0.91 (median 0.68). The sensitivity and specificity of the questionnaire for detecting high-alcohol, high-fat, low-calcium, and low-ascorbic acid consumers were 86.7% and 96.7%, 50.0% and 85.7%, 48.8% and 76.4%, and 61.9% and 70.0%, respectively. Receiver operating characteristic curves indicated comparable performance of the questionnaire and a three-day diet record, regarded as another screening test. The questionnaire performed poorly for other nutrients. The results indicate that our questionnaire is reasonably reproducible, comparable with the diet records, and useful as a screening test to detect high or low consumers of several nutrients associated with cancer for subsequent enrollment in dietary intervention trials or dietary counseling.

Impact of smoking habit on medical care use and its costs: a prospective observation of National Health Insurance beneficiaries in Japan

BACKGROUND

To quantify excess medical use associated with smoking, a large prospective cohort study is needed. The authors examined the impact of smoking on medical care use in a large population-based cohort with an accurate data collecting system in Japan.

METHOD

The data were derived from a 30-month prospective cohort study of 43,408 National Health Insurance beneficiaries aged 40--79 years living in a rural Japanese community. The smoking habit of beneficiaries was assessed in a baseline survey at the end of 1994. Medical care use and its costs were monitored by linkage with the National Health Insurance claim history files since January 1995.

RESULTS

Male smokers incurred 11% more medical costs (after adjustment for age, physical functioning status, alcohol consumption, body mass index and average time spent walking) than 'never smokers' but for female smokers and never smokers the costs were almost the same. This difference was mainly attributable to increased use of inpatient medical care among smokers, especially in males, where per month cost of inpatient care was 33% higher in smokers. Age-group specific analysis in men showed that excess mortality and excess medical cost ratio for smokers peaked in those aged 60--69 years.

CONCLUSIONS

Smokers consume excess medical care. Among the population aged 45 years and over, about 4% of total medical costs were attributable to smoking. To pursue both better health and lower medical costs for the nation, a comprehensive programme to reduce tobacco use is needed.

Medical cost for disability: a longitudinal observation of national health insurance beneficiaries in Japan

OBJECTIVES

To measure the impact of disability on the use of medical care and its costs.

DESIGN

A 1-year prospective cohort study of National Health Insurance beneficiaries in a rural Japanese community. Their physical function was examined by the Medical Outcomes Study questionnaire at the end of 1994; medical care and its costs were then monitored for 1 year.

SETTING AND PARTICIPANTS

Participants were the 49,364 subjects, aged 40 to 79 years, who were beneficiaries of National Health Insurance and lived in the catchment area of Ohsaki Public Health Center, Miyagi, Japan. The subjects were mainly farmers, self-employed persons, housewives, or pensioners.

MEASUREMENTS

Medical care utilization (number of outpatient visits and days of inpatient care) and the costs for each subject were obtained from National Health Insurance Claim History files. These measurements were collected from January to December 1995, and the relationship between physical functioning levels and medical costs was analyzed.

RESULTS

The medical costs per capita increased with poorer physical function. Medical costs among those with limitations in performing self-care increased by 4 times in men and 3 times in women compared with those with no functional limitation. In this cohort, the 4.3% of the subjects who were dependent in self-care used 15% of the total inpatient days and 10% of the total medical costs.

CONCLUSION

Treatment of patients with disability requires a huge amount of medical resources. There is an urgent need for cost-effective intervention programs for disability prevention, which could be offset against the cost for treating the disabled.