Medical expenditures of men with hypertension
and/or a smoking habit: a 10-year follow-up study
of National Health Insurance in Shiga, Japan
Koshi Nakamura1,2, Tomonori Okamura3, Takehito Hayakawa4, Hideyuki Kanda4, Akira Okayama5
and Hirotsugu Ueshima2,6, for the Health Promotion Research Committee of the Shiga National
Health Insurance Organizations7
Hypertension and smoking are major causes of disability and death, especially in the Asia-Pacific region, where there is a high
prevalence of a combination of these two risk factors. We attempted to measure the medical expenditures of a Japanese male
population with hypertension and/or a smoking habit over a 10-year period of follow-up. A cohort study was conducted that
investigated the medical expenditures due to a smoking habit and/or hypertension during the decade of the 1990s using existing
data on physical status and medical expenditures. The participants included 1708 community-dwelling Japanese men, aged
40–69 years, who were classified into the following four categories: ‘neither smoking habit nor hypertension’, ‘smoking habit
alone’, ‘hypertension alone’ or ‘both smoking habit and hypertension.’ Hypertension was defined as a systolic blood pressure of
X140mmHg, a diastolic blood pressure of X90mmHg or taking antihypertensive medications. In the study cohort, 24.9% had
both a smoking habit and hypertension. During the 10-year follow-up period, participants with a smoking habit alone (18444
Japanese yen per month), those with hypertension alone (21252 yen per month) and those with both a smoking habit and
hypertension (31037 yen per month) had increased personal medical expenditures compared with those without a smoking
habit and hypertension (17418 yen per month). Similar differences were observed even after adjustment for other confounding
factors (Po0.01). Japanese men with both a smoking habit and hypertension incurred higher medical expenditures compared
with those without a smoking habit, hypertension or their combination.
Hypertension Research (2010) 33, 802–807; doi:10.1038/hr.2010.81; published online 27 May 2010
Keywords: epidemiology; medical expenditures; smoking
Elevated blood pressure is the leading cause of death, as well as a
major cause of disability in the world.1,2Approximately 13.5% of all
deaths and 6.0% of all disability-adjusted life years among those aged
X30 years are attributable to high blood pressure with systolic blood
pressure of 4115mmHg.3This is because of the strong effect of
hypertension on the development of cardiovascular disease, including
coronary heart disease and stroke.4–7Hypertension is a major con-
tributor to cardiovascular diseases in the Asia-Pacific region.3Further-
more, cigarette smoking, which leads to cardiovascular disease as well
as cancer and respiratory disease,7–12is also a major health burden in
the Asia-Pacific region because of its popularity among men;13nearly
two-thirds of the world’s smokers live in 10 countries, and most of
them are in that region.14Thus, both hypertension and a smoking
habit might be more important determinants of human health than
other risk factors in the Asia-Pacific region.15–22For example, in
Japan, hypertension and a smoking habit contribute to 20.8 and
20.5% of deaths among men, respectively, which is much greater than
the mortality because of hypercholesterolemia (4.5%) or diabetes
(5.0%).15In addition, 20–30% of Japanese men are estimated to
have both hypertension and a smoking habit simultaneously,16,23and
the risk of cardiovascular disease is higher in these individuals than in
those with just one or neither of these two risk factors.6,7,11,12,16
The effect of hypertension and smoking should be considered from
the viewpoint of medical expenditures, particularly in the Asia-Pacific
region where there is a high prevalence of individuals with both of
these two risk factors. However, the majority of previous epidemio-
logical studies have only reported the association between a single risk
Received 12 January 2010; revised 17 March 2010; accepted 22 March 2010; published online 27 May 2010
1Department of Epidemiology and Public Health, Kanazawa Medical University, Uchinada, Japan;2Department of Health Science, Shiga University of Medical Science, Otsu,
Japan;3Department of Preventive Cardiology, National Cardiovascular Center, Suita, Japan;4Department of Hygiene and Preventive Medicine, Fukushima Medical University,
Fukushima, Japan;5The First Institute of Health Service, Japan Anti-Tuberculosis Association, Tokyo, Japan and6Lifestyle-Related Disease Prevention Center, Shiga University of
Medical Science, Otsu, Japan
7Members of the committee are listed in the Appendix.
Correspondence: Dr K Nakamura, Department of Epidemiology and Public Health, Kanazawa Medical University, 1–1 Daigaku, Uchinada, Ishikawa 920–0293, Japan.
Hypertension Research (2010) 33, 802–807
& 2010 The Japanese Society of Hypertension All rights reserved 0916-9636/10 $32.00
factor and medical expenditures.24–27We hypothesized that hyper-
tensive individuals with a smoking habit would incur higher future
medical expenditures, especially in-patient expenditures, than those
with just one or neither of these two risk factors because of a high
incidence of cardiovascular and other serious diseases. To test this
hypothesis, we attempted to measure the medical expenditures of
individuals with hypertension and/or a smoking habit over a 10-year
period in a community-based, male Japanese population.
In Japan, many medical services are provided by the public medical insurance
system,28–30which requires the enrollment of all Japanese residents (‘health-
insurance-for-all’). During the period when data were collected (from 1990 to
2001), public medical insurance consisted of two insurance systems. The
eligibility for each insurance system was as follows: the first system, named
Social Insurance, was for employees and their dependants and covered
approximately two-thirds of the overall Japanese population; the other system,
named National Health Insurance (NHI), was for those not covered by Social
Insurance, for example, self-employed individuals such as farmers and fisher-
men, as well as retirees and their dependants, and covered the remaining one-
third of the population. Prices were strictly controlled by a fee schedule set by
the National Government and were determined on a ‘fee-for-service’ basis. The
fee schedule was the same regardless of the insurance system. Furthermore, the
same fee schedule applied to all the clinics and hospitals given approval to
provide medical services under the public medical insurance system. However,
some medical services including health check-ups for asymptomatic individuals
and inoculations were not covered by medical insurance. The fee for these
services was recorded in an insurance claim history file.
In this study, we used the insurance claim history files to obtain information
on medical expenditures. Therefore, the medical expenditures in this study
were confined to the range of the fee schedule used in the public medical
insurance system in Japan. Total medical expenditures were divided into
outpatient and in-patient medical expenditures.
Study design and participants
The present cohort comprised 4535 Japanese beneficiaries of NHI, the
insurance system for self-employed individuals. The details of the present
cohort have been reported previously.25,31–33In brief, the study participants,
aged 40–69 years, lived in seven rural towns and a village in Shiga Prefecture,
West Japan, and had a voluntary baseline survey in 1989–1991. In 1990, the
study area had 82155 residents, including 31564 individuals aged 40–69 years,
of whom 11900 were NHI beneficiaries.34Therefore, the participants in this
study represented approximately 38% of all NHI beneficiaries aged 40–69 years
living in this area. The analysis was conducted only for men, because the
prevalence of smokers is quite low among Japanese women;8–10,16,23,35our data
showed that current smokers and former smokers accounted for 3.4% (n¼87)
and 0.5% (n¼14), respectively, of 2596 female participants. Of the 1939 male
participants, 231 were excluded because they were former smokers (n¼229) or
there was no information on smoking habit at the baseline survey (n¼2). We
excluded former smokers from the analysis because we wanted an exact
measure of medical expenditures related to smoking at baseline. The remaining
1708 participants were included in the analysis. Monthly NHI claim history
files of the Shiga NHI Organizations were linked with the baseline survey data
files at the organizations. To protect the participants’ privacy, their names were
deleted from the linked data at the organizations. Therefore, the data were
analyzed without knowledge of the participants’ identity. This study was
approved by the institutional review board of Shiga University of Medical
Science for ethical issues (no. 16–15).
The baseline survey was performed during the period 1989–1991 using
standardized methods in accordance with the Manual for Health Check-ups
under the Medical Service Law for the Aged, issued by the Japan Public Health
Association in 1987.36Blood pressures were measured by well-trained public
health nurses in the right arm in the sitting position using a standard mercury
sphygmomanometer after the participants had rested for at least 5min. The use
of antihypertensive medications and smoking habit were obtained from inter-
views conducted by well-trained public health nurses and medical doctors.
Hypertension was defined as a systolic blood pressure of X140mmHg,
a diastolic blood pressure of X90mmHg or taking antihypertensive medica-
tions. On the basis of this information, all eligible male participants were
classified into the following four categories: ‘neither smoking habit nor
hypertension’, ‘smoking habit alone’, ‘hypertension alone’ or ‘both smoking
habit and hypertension’. A drinking habit and a history of diabetes were also
evaluated by the interviews. Body height and weight were measured and
body mass index was calculated as body weight (kg) divided by the square
of body height (m2). Serum total cholesterol levels were measured by an
We calculated medical expenditures per person in each of the four categories
after a 10-year follow-up period. Information on medical expenditures for each
participant and information on participants who withdrew from the NHI or
those who died were obtained from the monthly NHI claim history files,
beginning in April of the year after their initial health check-up and continuing
until March 2001. Medical expenditures were expressed in Japanese yen, US
dollars and euros (100 Japanese yen¼1.08 US dollars or 0.76 euros, at the
foreign exchange rate on 1 September 2009). Data on medical expenditures for
each participant differed depending upon the period of subscription to the
NHI. The medical expenditures for each participant were therefore divided by
the period of subscription and expressed as expenditures per month of follow-
up. If a beneficiary withdrew from the NHI or died, follow-up was terminated
at that point. Follow-up was restarted for beneficiaries who withdrew and then
re-enrolled in the NHI. Reasons for withdrawal from the NHI included moving
to regions outside of Shiga Prefecture or transfer to the other insurance system.
Because the distribution of real medical expenditures was positively skewed, the
data were logarithmically transformed to normalize the distribution and the
results were expressed as geometric means. For participants with expenditures
of 0 yen per month, the logarithmic transformations were performed by
replacing 0 yen with 1 yen. There were four participants with total medical
expenditures of 0 yen and five participants with outpatient medical expendi-
tures of 0 yen. For comparison of total and outpatient medical expenditures per
person in each category, we performed an analysis of covariance with the
Bonferroni correction to adjust the P-value for multiple post hoc comparisons.
The analysis of covariance incorporated the following variables as covariates:
age (40–44, 45–49, 50–54, 55–59, 60–64 or 65–69 years old, using five dummy
variables with 40–44 as a reference), body mass index, drinking habit (non-,
current occasional or current daily drinker, using two dummy variables with
non-drinkers as a reference), serum total cholesterol and a history of diabetes.
Because 896 participants (52.5%) had in-patient medical expenditures of 0 yen,
logarithmic transformations were not performed, and the Kruskal–Wallis test
was used to compare in-patient medical expenditures among the four cate-
gories. A similar analysis was repeated after excluding participants who were
taking antihypertensive medications at baseline.
In addition, to clarify whether medical expenditures associated with smok-
ing and/or hypertension increase over time because of the occurrence of
cardiovascular and other serious diseases, we calculated medical expenditures
per person in each of the four categories for the overall follow-up period of 10
years and also stratified expenditures by the follow-up period (the first 5 years
and the latter 5 years), using subgroups inwhich every participant was followed
for 45 years.
Finally, we examined excess medical expenditures attributable to hyperten-
sion and/or a smoking habit in the study population using the arithmetic
means of total medical costs in each category. The excess medical expenditures
attributable to hypertension and/or a smoking habit were calculated as follows:
(total medical expenditures in the ‘smoking habit alone’, ‘hypertension alone’,
and ‘both smoking habit and hypertension’ category–total medical expendi-
tures in the ‘neither smoking habit nor hypertension’ category) ? number of
participants in the ‘smoking habit alone’, ‘hypertension alone’ and ‘both
smoking habit and hypertension’ category.
Hypertension, smoking and medical expenditures
K Nakamura et al
The statistical analysis was performed using SPSS 14.0J for Windows (SPSS
Japan, Tokyo, Japan). The P-values were two sided and P-values of o0.05 were
considered statistically significant.
Current smokers accounted for 68.1% of the 1708 male study
participants, whereas hypertensive individuals accounted for 36.9%
of the cohort. Table 1 summarizes the baseline risk characteristics of
the male participants, grouped according to their smoking habit and
hypertension status. Of the study population, 24.9% had both a
smoking habit and hypertension, whereas 43.2% had smoking habit
alone and 11.9% had hypertension alone. The ‘both smoking habit
and hypertension’ group had the highest mean age. Only approxi-
mately 1% of the participants in each category had a history of
cardiovascular disease, and no remarkable differences were observed
among the four categories.
Total person-years were 15508 and the mean follow-up time was
9.1 years. As shown in Table 2, during the 10-year follow-up period,
total medical expenditures per person in the ‘both smoking habit and
hypertension’ category (31037 Japanese yen per month) tended to be
higher than in the ‘neither smoking habit nor hypertension’ category
(17418 yen per month), in the ‘smoking habit alone’ category (18444
yen per month) and in the ‘hypertension alone’ category (21252 yen
per month). For the multivariate-adjusted geometric means of total
medical expenditures, the differences among the four categories were
statistically significant (Po0.01). Similar statistically significant differ-
ences were also observed in outpatient medical expenditures
(Po0.01). In addition, in-patient medical expenditures showed sta-
tistically significant differences among the four categories (Po0.01).
Subgroup analysis, in which participants taking antihypertensive
medications at baseline were excluded (n¼80), showed a broadly
similar pattern; total medical expenditures per person were 19084 yen
per month for the ‘hypertension alone’ category (n¼172) (outpatient,
11108 yen; and in-patient, 7976 yen) and 31263 yen per month for
the ‘both smoking habit and hypertension’ category (n¼378) (out-
patient, 13658 yen; and in-patient, 17604 yen; data not shown in the
table). However, the difference in medical expenditures, especially for
outpatients, between the ‘hypertension alone’ category and the
‘neither smoking habit nor hypertension’ category was attenuated.
Table 3 shows medical expenditures per person grouped by smoking
habit and hypertension status for the overall follow-up period of 10
years and also stratified by the follow-up period, which was derived
from subgroups in which all participants had 45 years of follow-up
(n¼1491). The differences in medical expenditures, especially in-
patient expenditures, among the four categories were much greater
in the latter 5 years of follow-up than in the first 5 years.
Compared with the ‘neither smoking habit nor hypertension’
category, the excess medical expenditures attributable to a smoking
habit alone were estimated to be 757188 yen per month, and were
calculated as follows: (18444 yen–17418 yen) ? 738 participants with
a smoking habit alone. Accordingly, the excess medical expenditures
attributable to a smoking habit alone represented 2.0% of the total
medical expenditures for the 1708 participants (37090403 yen),
and were calculated as follows: 757188 yen/37090403 yen. Using
similar methods, the excess medical expenditures attributable to
hypertension alone and both a smoking habit and hypertension
were estimated to be 782136 yen and 5801694 yen, respectively,
which represented 2.1 and 15.6% of the total medical expenditures for
the study cohort.
We carried out a 10-year follow-up study between 1990 and 2001 and
showed that Japanese men with a smoking habit alone, hypertension
alone or both a smoking habit and hypertension had increased
personal medical expenditures compared with those without a smok-
ing habit and hypertension. The coexistence of these two risk factors
further increased medical expenditures in comparison with the
existence of just one of these two risk factors. The increments in the
expenditures associated with both or just one of these two risk factors
were prominent in the latter period of follow-up. The sum of excess
medical expenditures attributable to hypertension and/or a smoking
habit represented approximately 20% of the total medical expendi-
tures of the study cohort. An important strength of our study was that
the participants consisted of community-based individuals who were
beneficiaries of one of the public medical insurance systems on the
basis of ‘health-insurance-for-all’ in Japan. Therefore, our data can
probably be generalized to the Japanese male population. An addi-
tional strength of our study was that the 10-year follow-up period was
long enough to provide an accurate evaluation of medical expendi-
tures associated with serious conditions caused by smoking and
hypertension. This allowed the calculation of medical expenditures
stratified by the follow-up period.
Table 1 Baseline risk characteristics in 1989–1991 of 1708 male National Health Insurance beneficiaries in Shiga, Japan, grouped by
smoking habit and hypertension status
Smoking habit and hypertension category
NeitherSmoking aloneHypertension aloneBothP-value
Number of participants (distribution (%))
Body mass index (kgm–2)a
Occasional drinker (%)
Daily drinker (%)
Serum total cholesterol (mmoll–1)a
History of diabetes (%)b
Medication for hypertension (%)b
History of cardiovascular disease (%)b
aValues show the mean±s.d.; groups were compared by one-way analysis of variance.
bThe w2-test; medication for hypertension was compared only between the ‘hypertension-alone’ group and the ‘both’ group.
Hypertension, smoking and medical expenditures
K Nakamura et al
Our data showed that hypertension alone or a smoking habit alone
increased total medical expenditures by 3834 yen and 1026 yen,
respectively, which represented a 22 and 6% increment compared
with the expenditures of individuals without either risk factor. Medical
expenditures in the participants with hypertension alone tended to
be higher than in those with a smoking habit alone. This may be
reasonable, because the treatment of hypertension usually requires
antihypertensive medications, and this directly increases medical
expenditures, especially for outpatients. The results from our sub-
group analysis after excluding participants with antihypertensive
medications at baseline support this explanation. At the time of our
study, any medical services for smoking cessation, including nicotine
replacement therapy, were not provided by the public medical
insurance system in Japan. However, the analysis stratified by the
follow-up period showed a further increment in expenditures,
especially in-patient expenditures, of participants with smoking
alone in the latter 5 years of follow-up. These results suggest that
smoking increases medical expenditures later because of the occur-
rence of serious diseases. A similar explanation may be applicable to
increased medical expenditures of participants with hypertension
alone in the later period, which may be because of the use of
antihypertensive medications as well as the occurrence of cardiovas-
cular disease. However, we could not identify the particular disease or
event that directly increased medical expenditures among participants
with either hypertension or smoking.
The coexistence of a smoking habit and hypertension was identified
in approximately 25% of the study cohort and increased total medical
expenditures by 13619 yen. This represented a 78% increment
Table 2 Medical expenditures per person grouped by smoking habit and hypertension status, after a 10-year follow-up from 1990 to 2001,
based on National Health Insurance in Shiga, Japan
Medical expenditures per person per month
Smoking habit and hypertension categoryArithmetic mean Adjusted geometric meanArithmetic mean Adjusted geometric meanArithmetic mean
Neither (n¼340)17418 yen
6782 yen8508 yen
4994 yen8910 yen
Smoking alone (n¼738)7066 yen 4713 yen
Hypertension alone (n¼204) 9072 yen 6674 yenwz
At the foreign exchange rate on 1 September 2009, 100 Japanese yen¼1.08 US dollars or 0.76 euros.
aAnalysis of covariance adjusted for age, body mass index, drinking habit, serum total cholesterol and a history of diabetes.
wPo0.05 vs. neither, for multiple post hoc comparisons with Bonferroni correction.
zPo0.05 vs. smoking alone, for multiple post hoc comparisons with Bonferroni correction.
Table 3 Medical expenditures per person grouped by smoking habit and hypertension status, after a 10-year follow-up from 1990 to 2001,
based on National Health Insurance in Shiga, Japan
Medical expenditures per person per month (arithmetic mean)
Smoking habit and hypertension category 10 years
First 5 years /
latter 5 years10 years
First 5 years /
latter 5 years10 years
First 5 years /
latter 5 years
Neither (n¼301)12311 yen10162 yen
7945 yen 6742 yen
4366 yen3420 yen
Smoking alone (n¼649)14810 yen8345 yen6482 yen
Hypertension alone (n¼172)20929 yen 14345 yen6584 yen
Both (n¼369)26693 yen 13920 yen12773 yen
The data were derived from subgroups in which every participant was followed for 45 years, and are presented for the overall follow-up period of 10 years and also stratified by the follow-up period.
At the foreign exchange rate on 1 September 2009, 100 Japanese yen ¼1.08 US dollars or 0.76 euros.
Hypertension, smoking and medical expenditures
K Nakamura et al
compared with the expenditures of individuals with neither risk factor.
NIPPON DATA8016and the Hisayama study11reported that Japanese
who had both hypertension and a smoking habit were at increased risk
of cardiovascular disease compared with those who had either risk
factor alone or neither risk factor. These previous reports provide one
possible explanation for our findings of increased medical expendi-
tures of hypertensives with a smoking habit compared with the other
three categories. Alternatively, the effect of smoking on cancer and
respiratory disease8,9might have contributed to the increased medical
expenditures among hypertensives with a smoking habit. Our data on
the time-related changes of medical expenditures during the follow-up
period support these possible explanations, as there was a 232%
increment in future expenditures of individuals with both risk factors
compared with individuals with neither risk factor.
The mean level of blood pressure is higher in Japan than in Western
countries,17,35,37–41despite a substantial decline in blood pressure
during the past four decades.42In addition, the prevalence of smoking
among Japanese men remains much higher compared with men in the
West,8–10,17,35,37,41,43although there has been a trend for a decline in
smoking.42As a result, approximately 70–80% of Japanese men have
hypertension and/or a smoking habit,16,23which would directly
contribute to as much as 20% of the entire medical expenditures in
this population. Individuals with the coexistence of both these two
risk factors comprise approximately 20–30% of the Japanese male
population.16,23It should be noted that the combination of hyper-
tension and smoking would contribute to approximately 15% of total
medical expenditures, not only because of the substantially high value
of medical expenditures but also because of the high prevalence of
individuals with the coexistence of both risk factors. As the relative
importance of hypertension and smoking on human health is likely to
be similar among Japan and other Asia-Pacific countries such as China
and Korea,17–22a broadly similar pattern of increased medical expen-
diture may be observed in these countries as well.
This study has several limitations. First, although the participants
were selected from a community-based population whose health
status was relatively typical of the overall Japanese population,28the
participants were limited to NHI beneficiaries belonging to self-
employed occupational groups in one area of Shiga prefecture. The
socio-economic status and lifestyle of these beneficiaries may have had
an effect on their health. In addition, the study participants may have
been concerned about their heath status, because they voluntarily
underwent the survey. Moreover, no information on a history of
serious disease other than cardiovascular diseases was available at
baseline. However, the study participants consisted of healthy com-
munity-dwelling individuals who participated in the baseline survey
without the need of assistance. We therefore believe that most of the
participants were free of serious disease at baseline, as a history of
cardiovascular disease was identified at baseline in only 0.7% of the
participants. Second, the public medical insurance system in Japan
differs from that in other countries. Therefore, absolute values of
medical expenditures estimated in this study should not be directly
comparable to other populations, and our results cannot necessarily
be extrapolated to other populations. Third, blood pressure was
measured only once in each participant, and classification of partici-
pants based on this single measurement may have overestimated the
prevalence of hypertension. This misclassification may consequently
have led to the underestimation of differences in medical expenditures
between the hypertensive and non-hypertensive groups. In addition,
we had no serial data on smoking habit and hypertension after the
baseline survey. Despite the lack of serial data, we believe that our
results, based on a single baseline survey and 10-year follow-up,
support our conclusion that hypertensive individuals with a smoking
habit incur higher medical expenditures in the future. Fourth, our
analysis did not account for the severity of hypertension or the
amount of tobacco smoking because the number of eligible partici-
pants was not large enough to stratify hypertension and smoking
status. Finally, the details of the medical diagnoses, medical treatment
status (for example, prescriptions), clinical condition and cause of
mortality were not available in this study. Thus, further studies are
needed to clarify the effect of these variables. However, our subgroup
analysis provided important evidence that antihypertensive medica-
tions significantly increase medical expenditures, especially outpatient
In conclusion, hypertensive individuals with a smoking habit incur
higher medical expenditures in the Japanese male population. Atten-
tion should be paid to such individuals, especially in countries where
both hypertension and a smoking habit are prevalent. To reduce the
economic burden on the health-care system because of hypertension
and smoking, efforts should be made to prevent and treat hyper-
tension and to encourage individuals not to smoke, especially before
the occurrence of serious diseases that increase medical expenditures.
CONFLICT OF INTEREST
The authors declare no conflict of interest.
This study was performed as part of the researchwork of the Health Promotion
Research Committee of the Shiga NHI Organizations. We are grateful to the
Shiga NHI Organizations. This study was funded by research grants from the
Ministry of Health, Labour and Welfare (Comprehensive Research on Cardi-
ovascular and Life-Style Related Disease: H17-kenko-007, H18-seishuu-012,
H20-seishuu-013; H22-seishuu-012; Research on Cardiovascular Disease: 20K-6).
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The Health Promotion Research Committee of the Shiga National
Health Insurance Organizations
Chairman: Hirotsugu Ueshima.
Participating researchers: Shigeo Yamashita, Tomonori Okamura,
Yoshinori Tominaga, Kazuaki Katsuyama, Fumihiko Kakuno and
Associate researchers: Koshi Nakamura and Hideyuki Kanda.
Secretary members: Yukio Tobita, Kanehiro Okamura, Kiminobu
Hatta, Takao Okada and Michiko Hatanaka.
Hypertension, smoking and medical expenditures
K Nakamura et al