Prevalence, awareness, treatment, control and risk factors of hypertension in Korea: the Ansan study

Prevalence, awareness, treatment, control and risk factors of
hypertension in Korea: the Ansan study
Inho Jo
a
, Younjhin Ahn
a
, Jungbok Lee
b
, Kyung Rim Shin
c
, Hong Kyu Lee
a,d
and
Chol Shin
b
Objectives To determine prevalence, awareness,
treatment, and control of hypertension, and its risk factors
in an urban Korean population.
Design and setting A cross-sectional survey in Ansan-city,
Korea.
Subjects and methods Population-based samples of
people aged 18±92 years in Ansan-city, Korea, were
selected, yielding 2278 men and 1948 women, and their
blood pressures were measured using a highly
standardized protocol. Hypertension was de®ned as a
systolic BP > 140 mmHg or diastolic BP > 90 mmHg or
reported treatment with antihypertensive medications, and
subclassi®ed according to 1999 WHO-ISH guidelines.
Isolated systolic hypertension (ISH) de®ned as a systolic
BP > 140 mmHg and diastolic BP < 90 mmHg was also
examined. Data were strati®ed by age and sex.

Results The overall prevalence of hypertension in this
study was 33.7%. Among these, 64.9% had Grade 1
hypertension, 22.5% Grade 2, and 12.5% Grade 3. Age-
speci®c prevalence of hypertension increased
progressively with age, from 14.19% in 18 to 24 year-olds
to 71.39% in those 75 years or older. Hypertension
prevalence was signi®cantly higher in men (41.5%) than in
women (24.5%) (P < 0.001). Isolated systolic hypertension
had signi®cantly lower prevalence (4.33%) within the
population, although in the elderly aged 55 years or more it
rose by 11.13%. Overall, 24.6% of hypertensive individuals
were aware that they had high blood pressure, as much as
78.6% were being treated with antihypertensive
medications, and 24.3% were under control. Hypertension
awareness as well as treatment and control rates varied by
sex, with women higher in all three rates. Multivariate
analysis revealed that age, body mass index and abdomen
circumference were signi®cantly associated with
prevalence of hypertension both in men and women.
Conclusions Hypertension is highly prevalent in Korea.
Despite the high rate of treatment, the rates of awareness
and control are relatively low, suggesting the nationwide
demand for preventing and controlling high blood pressure
in Korea in order to avert an epidemic of cardiovascular
disease. J Hypertens 19:1523±1532 & 2001 Lippincott
Williams & Wilkins.
Journal of Hypertension 2001, 19:1523±1532
Keywords: awareness, control, hypertension, Korea, prevalence, risk factor,
treatment
a

Division of Cardiovascular Research, Department of Biomedical Sciences,
National Institute of Health, Seoul, Korea,
b
Ansan Health Center, Korea University
Hospital, Ansan-city, Kyonggi-do, Korea,
c
College of Nursing Science, Ewha
Womans University, Seoul, Korea, and
d
Division of Endocrinology and
Metabolism, Department of Internal Medicine, College of Medicine, Seoul
National University, Seoul, Korea.
Sponsorship: This work was supported in part by National Institute of Health,
Korea grant no. 334±6113±211±207±00 (I.J.) and by Korea University
Institutes of Medical Science grant 2000±n6 (C.S.).
Correspondence and requests for reprints to Chol Shin, M.D. F.C.C.P., Ph.D.
Ansan Health Center, Korea University Hospital, 516 Gojan-dong,
Ansan-city, Kyonggi-do, (425±707), Korea.
Tel: 82 31 412 5602; fax: 82 31 412 5604; email:
Received 28 December 2000 Revised 16 March 2001
Accepted 11 April 2001
Introduction
The improved control of infectious and parasitic dis-
eases and the sharp decrease in infant mortality during
recent decades have dramatically changed the health
pro®le of many developing countries [1]. This is
re¯ected in an increase in life expectancy and the
emergence of cardiovascular diseases (CVD) as a lead-
ing cause of morbidity and mortality in such countries
[2]. In fact, CVD including stroke are still the leading

cause of all death in Korea [3], which accounted for
23.3% in 1999, although in 1983 it was responsible for
as high as 27.8% of nation's mortality.
Recognizing the rapid emergence of CVD as a clinical
and public concern in Korea, the nationwide Korea
Health and Nutrition Survey was initiated in 1998 to
assess the prevalence of selected life-style-related dis-
eases and their risk factors including hypertension. No
of®cial results from Korea Health and Nutrition Survey
have been, however, published to date.
High blood pressure (BP) is one of the most important
risk factors for CVD, and it has been shown that the
reduction of highly or moderately elevated BP levels
results in a decrease in stroke and myocardial infarction
rates [4,5]. One of the cornerstones of the primary
prevention of CVD since the early 1970s has focused
on screening and early antihypertensive drug treatment
Original article 1523
0263-6352 & 2001 Lippincott Williams & Wilkins
of subjects presenting high BP [6]. Although commu-
nity-based or national programs for detection and treat-
ment of hypertension have been carried out in many
countries [7±14], only a few studies of hypertension
prevalence have been done in Korea [15±17]. Further-
more, these studies were con®ned to analyses from 8 to
10-year-old surveys. In order to better assess the
current status of hypertension screening and manage-
ment, we recorded measurements of hypertension pre-
valence, awareness, treatment and control in a
randomized Korean population.

Materials and methods
Subjects
The study area from which the participants were
recruited is situated in a southwestern part of Seoul
named Ansan-city, Kyonggi-do in South Korea, and is
characterized by a newly industrializing town from a
farming county. The city comprises 250 000 population
aged more than 18 years. The target study sample was
4700 subjects aged more than 18 years who were
randomly selected based upon address codes from June
1999 to April 2000. All were visited and interviewed by
well-trained nursing students. A total of 427 subjects
(9.09%) refused to participate in the survey. Further-
more, we failed to collect suf®cient information regard-
ing a detailed history and examination from 47 other
subjects. Complete data for the analysis of hypertension
and possible risk factors in this study were, therefore,
available and based on the remaining 4226 subjects
(2278 men, 1948 women).
Questionnaires and blood pressure measurement
The survey team consisting of nursing students was
well trained in the details of questionnaires and meas-
urements before starting the survey. In particular, all
the surveyors were encouraged to read BP readings
within a 2 unit error on their sequential measurements
during practice. A team of two surveyors visited each
home and interviewed the volunteer subjects. Only one
person aged more than 18 years within the households
was asked to participate in an interview. While one
surveyor interviewed the study subject, the other asked

another individual within the household for con®rma-
tion of the data. Detailed information included sex,
weight (portable scales: SECA, Hamburg, Germany;
calibration monthly), height (steel ruler), abdomen
circumference, alcohol intake, smoking, household in-
come, occupation, marital status, years of education,
driving, and BP. BP was measured according to World
Health Organization-International Society of Hyper-
tension (WHO-ISH) guidelines [18] using Bauman-
ometer
1
(WA Baum Co. Inc. Copiague, New York,
USA). Three BP readings were taken on either arm
with 5 min intervals. Subjects were seated and caffeine
substances and smoking were restricted for 30 min
before the measurement. Data presented here are the
average of three measurements.
De®nitions
Hypertension was de®ned as a systolic BP >
140 mmHg or diastolic BP > 90 mmHg according to
WHO-ISH criteria [18] or a subject's currently receiv-
ing antihypertensive treatments to control hyper-
tension, regardless of the measured level. We further
classi®ed the severity of hypertension as normal (systo-
lic BP , 140 mmHg and diastolic BP , 90 mmHg),
Grade 1 (140±159 for systolic BP/90±99 mmHg for
diastolic BP), Grade 2 (160±179/100±109 mmHg), and
Grade 3 (> 180/110 mmHg). Isolated systolic hyper-
tension (ISH) was de®ned as a systolic BP >
140 mmHg and diastolic BP , 90 mmHg. Body mass

index (BMI) was calculated from the simple equation
(body weight in kg divided by height in m
2
). Smoking
was classi®ed as current, ex- (not for at least 1 year),
and non-smoker. Alcohol intake was classi®ed as drin-
ker and non-drinker from self-administered question-
naire. Awareness of hypertension was de®ned as a
subject who reported a history of previous diagnosis of
hypertension or high BP. Treatment of hypertension
was de®ned as a subject who currently uses prescribed
antihypertensive drugs. Control of hypertension was
de®ned as a subject who was receiving treatment for
hypertension and kept BP normal (systolic
BP , 140 mmHg and diastolic BP , 90 mmHg).
Data analysis
All the data of this study were summarized as mean
and standard deviation for continuous variables and as
frequency and percentage for categorical variables.
Intergroup comparison for risk factors among subjects
with or without hypertension was performed using a ÷
2
test for distribution and t-test for continuous variables.
The signi®cance of various risk factors was calculated
by logistical regression analysis where the odds ratio
and 95% con®dence intervals (CI) were calculated
using multivariate analysis. All the analyses were con-
ducted using the statistical software package SAS V6.12
[19] and a probability value of P , 0.05 was considered
to be signi®cant.

Results
General characteristics
The mean age of the study participants was 45.3 Æ 17.9
(mean Æ SD) years (range 18±92 years). The mean age
(46.5 Æ 17.2) of the men was slightly, but statistically
signi®cantly higher than that (44 Æ 18.6) of the women.
All anthropometric data tested in this study was sig-
ni®cantly higher in men than in women. A total of 21%
of the population had attended at least high school.
Generally, men had higher education levels than wo-
men. The majority had a partner (75.1% of the men
and 65.7% of the women) and occupation (77.9% of the
1524 Journal of Hypertension 2001, Vol 19 No 9
men and 74.2% of the women). Other detailed life style
characteristics for the study population are shown in
Table 1.
Blood pressure
BP distributions were approximately Gaussian, with a
rightward skew (Fig. 1). Mean systolic and diastolic BP
(mmHg) was 128.9 Æ 18.0 and 83.6 Æ 12.9 for men; and
121.1 Æ 18.1 and 77.3 Æ 12.6 for women, respectively
(Table 1). Figure 2 displays the mean systolic and
diastolic BP by age and sex. Mean systolic BP rose
progressively across entire age range. The slope of the
rise in systolic BP was bigger in women than in men.
Although systolic BP in women was signi®cantly lower
before the age of 54 (P , 0.01), it appeared that there
was no signi®cant difference between 55 and 74 years
of age (P . 0.05), and even a reversal was noted after
75 (P , 0.05). The pattern for mean diastolic BP was

similar at a younger age (before the age of 45), but the
average level of diastolic BP plateaued in men after the
age of 45 and in women after the age of 55, respec-
tively. Mean diastolic BP was almost the same in both
men and women after the age of 55 years.
Prevalence of hypertension
Table 2 presents the age±sex-speci®c and age±sex-
adjusted prevalence of hypertension. Overall, 33.7% of
all studied population were hypertensive. Hypertension
appeared to be signi®cantly more common in Korean
men (41.53%) than women (24.54%) (P , 0.001).
Hypertension prevalence increased progressively with
age. In the youngest age group (18±24 years) hyper-
tension was present in 14.19% of the population,
whereas the prevalence rate was 71.39% in the oldest
age group (75±92 years). National estimates of the
hypertension prevalence were calculated using the
available census data in 1995 [20], resulting in 35.8,
21.6 and 28.6% in age-adjusted men, women, and age±
sex-adjusted total population of Korea, respectively
(Table 2). Using subclassi®cation of BP according to
WHO-ISH guidelines, 64.9% of hypertensive popu-
lation excluding antihypertensive drug takers had
Grade 1 BP; 22.5% Grade 2, 12.5% Grade 3, as shown
in Table 3. Hypertension severity varied signi®cantly
until the age of 54, showing increases in both Grade 2
and 3 BPs compared with decrease in Grade 1 BP.
After the age of 55, however, the prevalence of each
Grade BP remained relatively constant. Grade 1 BP
reading was most prevalent (89.1%) between the age of

18±24 years. No signi®cant difference was found in the
severity of sex-speci®c hypertension. Table 4 shows the
age- and sex-speci®c prevalence of ISH. The overall
prevalence of ISH in the studied population was 4.33%,
and it signi®cantly (P , 0.001) increased with age.
Furthermore, the prevalence of ISH rose signi®cantly
from 1.36% in all population aged 18±54 years to
Table 1 General characteristics of study population
Men (n  2278) Women (n  1948) All (n  4226)
Mean Æ SD
Age (years)
ÃÃÃ
,
y
46.5 Æ 17.2 44.0 Æ 18.6 45.3 Æ 17.9
SBP (mmHg)
ÃÃÃ
128.9 Æ 18.0 121.1 Æ 18.1 125.3 Æ 18.4
DBP (mmHg)
ÃÃÃ
83.6 Æ 12.9 77.3 Æ 12.6 80.7 Æ 13.1
Height (cm)
ÃÃÃ
169.3 Æ 6.1 157.3 Æ 6.4 163.8 Æ 8.6
Weight (kg)
ÃÃÃ
66.2 Æ 9.3 55.0 Æ 8.2 61.0 Æ 10.4
Abdomen circumference (cm)
ÃÃÃ
86.9 Æ 10.6 82.2 Æ 13.4 84.7 Æ 12.2

BMI (kg/m
2
)
ÃÃÃ
23.1 Æ 2.8 22.3 Æ 3.3 22.7 Æ 3.1
Number of subjects (%)
Years of education (%)
Ã
< 12 years 1650 (72.4) 1673 (85.9) 3323 (78.6)
. 12 years 628 (27.6) 275 (14.1) 903 (21.4)
Marital status (%)
Ã
Single 567 (24.9) 669 (34.3) 1236 (29.3)
Couple 1711 (75.1) 1279 (65.7) 2990 (70.7)
Occupation (%)
Ã
Yes 1775 (77.9) 1446 (74.2) 3221 (76.2)
No 503 (22.1) 502 (25.8) 1005 (23.8)
Household income (US$/month) (%)
Ã
, 800 824 (36.2) 600 (30.8) 1424 (34.0)
800±1600 908 (39.9) 797 (40.9) 1705 (40.7)
1600±2500 331 (14.5) 360 (18.4) 691 (16.5)
> 2500 203 (8.9) 164 (8.4) 367 (8.8)
Alcohol intake (%)
Ã
Yes 1490 (65.5) 648 (33.4) 2138 (50.8)
No 783 (34.5) 1290 (66.6) 2073 (49.2)
Smoking status (%)
Ã

Current smoker 1308 (57.5) 116 (2.7) 1424 (33.7)
Ex-smoker 361 (15.8) 16 (0.4) 377 (8.9)
Nonsmoker 609 (26.7) 1816 (43.0) 2425 (57.4)
SBP, systolic blood pressure; DBP, diastolic blood pressure; BMI, body mass index.
y
Means of variables
were signi®cantly different between men and women,
ÃÃÃ
P , 0.001. Distributions of subjects were
signi®cantly different among variable categories and between gender,
Ã
P , 0.05.
Hypertension in Korea Jo et al. 1525
11.13% in those aged 55±92 years. In the elderly (after
the age of 55), the prevalence of ISH in men and
women was 10.56 and 11.92%, respectively, showing
that ISH appeared to be more common in women than
in men in this age group, however, no gender differ-
ence in the prevalence of ISH was found (P  0.512).
Hypertension awareness, treatment, and control
Table 5 showed that approximately a quarter (24.6%)
of the studied population who could be classi®ed as
hypertensive, were aware of their high BP. Rates of
awareness were higher in women (33.5%) than men
(20.1%) (P , 0.001). The estimated percentage of
hypertensive individuals receiving pharmacological
treatment in Korea was 78.6%. A higher proportion of
women (85.0%) were being treated than men (73.2%)
(P , 0.01). The estimated percentage of hypertensive
individuals whose BPs were under control (systolic

BP , 140 mmHg and diastolic BP , 90 mmHg) was
24.3%. Better control rates were noted in women
(27.9%) than men (20.9%), but no signi®cant difference
was found (P  0.354).
Risk factors associated with hypertension
The demographic, anthropometric and lifestyle charac-
teristics of subjects with or without hypertension were
presented in Table 6. The prevalence of hypertension
in both genders was associated with greater age
(P , 0.001). Hypertension was also signi®cantly asso-
ciated with higher body mass index (BMI), greater
abdomen circumference, years of education, marital
status, occupation, driving, smoking, and lower house-
hold income in both genders. Alcohol intake was
associated with hypertension in women (P , 0.01), but
not in men. When age-adjusted, BMI and abdomen
circumference in men had a strong dose±response
relationship over their entire ranges as shown in Table
7. In women, however, these relationships were only
true at BMI > 26 kg/m
2
and abdomen circumference .
95 cm. Hypertension was signi®cantly less prevalent in
those who earned the highest incomes in both genders
(P , 0.01). Interestingly, alcohol intake was associated
Fig. 1
Bar graphs showing distribution of (a) systolic and (b) diastolic blood
pressures in the Ansan adult population.
0
200

400
600
800
1000
1200
Number of subjects
Ͻ60
60Ϫ
70Ϫ
80Ϫ
90Ϫ
100Ϫ
110Ϫ
120Ϫ
130Ϫ
140Ϫ
150Ϫ
160Ϫ
170Ϫ
180Ϫ
190Ϫ
200Ϫ
SBP (mmHg)
(a)
0
200
400
600
800
1000

1200
1400
1600
Number of subjects
Ͻ40
40Ϫ
50Ϫ
60Ϫ
70Ϫ
80Ϫ
90Ϫ
100Ϫ
110Ϫ
120Ϫ
130Ϫ
140Ϫ
DBP (mmHg)
(b)
SBP-M SBP-F DBP-M DBP-F
50
70
90
110
130
150
BP (mmHg)
18–24 25–34 35–44 45–54 55–64 65–74 75–92
Age group (years)
c
c

bc
c
b
c
a
b
a
a
a
a
a
a
d
d
d
d
d
d
c
c
b
b
a
a
a
a
*
***
***
***

***
***
*** ***
***
Fig. 2
Line graph shows systolic blood pressure (SBP) and diastolic blood
pressure (DBP) by age and sex (M, male; F, female) among the Ansan
adult population. Different letters means signi®cantly different group at
P  0.0001 by analysis of variance (ANOVA) test.
Ã
P , 0.01;
ÃÃÃ
P , 0.001) in SBP and DBP between men and women of same
age group.
Table 2 Prevalence of hypertension by age and sex group (%)
Age group Men Women All
18±24 25.0 6.2 14.2
25±34 30.1 6.7 18.3
35±44 34.8 9.6 22.2
45±54 42.6 28.2 36.9
55±64 51.5 57.1 51.8
65±74 62.0 59.0 59.4
75±92 66.2 76.6 71.4
Crude prevalence
ÃÃÃ
,
y
41.5 24.5 33.7
National estimate 35.8 21.6 28.6
§

Hypertension, diastolic blood pressure > 90 mmHg or systolic blood
pressure > 140 mmHg.
y
Crude prevalence was signi®cantly different between
men and women,
ÃÃÃ
P , 0.001.
§
Age-sex-adjusted hypertension prevalence by
the total population of Korea in 1995.
1526 Journal of Hypertension 2001, Vol 19 No 9
with hypertension only in men, not in women, after age
adjustment (Table 7). In comparison, as shown in
Table 6, a signi®cant relationship with alcohol was
observed only in women, not in men, without age
adjustment. No signi®cant relationships with all other
lifestyles were observed in both genders after age
adjustment (Table 7). Multivariate logistic regression
analysis showed that regardless of age and sex, in men,
age, BMI, abdomen circumference and alcohol intake
were independent risk factors and showed strong
association with hypertension (Table 8). In women,
however, alcohol intake lost its signi®cance. Only weak,
but still signi®cant association was observed with BMI
in women (P  0.07). No independent associations with
hypertension were found with years of education,
occupation, household income and smoking in both
genders.
Discussion
Our results showed that the overall prevalence of

hypertension, estimated to be 33.7%, exceeds those of
many countries [8,21±24]. This is especially noteworthy
because this study included a comparatively younger
( > 18 years old) age group than other studies. In many
Table 3 The severity of hypertension by age and sex according to World Health Organization-International Society of Hypertension (WHO-
ISH) criteria (%)
Age categories 18±24 25±34 35±44 45±54 55±65 65±74 75±92 Total
Hypertension 65 161 250 176 218 312 242 1424
Severity
Grade 1 (mild) 57 (89.1) 121 (76.1) 168 (70.0) 89 (58.9) 95 (59.4) 127 (58.3) 89 (56.7) 46 (64.9)
Grade 2 (moderate) 6 (9.4) 26 (16.4) 45 (18.8) 39 (25.8) 41 (25.6) 58 (26.6) 44 (28.0) 259 (22.5)
Grade 3 (severe) 1 (1.6) 12 (7.5) 27 (11.3) 23 (15.2) 24 (15.0) 33 (15.1) 24 (15.3) 144 (12.5)
Men 48 132 191 111 122 139 64 807
Grade 1 (mild) 41 (85.4) 100 (75.8) 130 (68.1) 63 (56.8) 74 (60.7) 78 (56.1) 38 (59.4) 524 (64.9)
Grade 2 (moderate) 6 (12.5) 22 (16.4) 36 (18.8) 27 (24.3) 31 (25.4) 40 (28.8) 15 (23.4) 177 (21.9)
Grade 3 (severe) 1 (2.1) 10 (7.6) 25 (13.1) 21 (18.9) 17 (13.9) 21 (15.1) 11 (17.2) 106 (13.1)
Women 16 27 49 40 38 79 93 342
Grade 1 (mild) 16 (100) 21 (77.8) 38 (77.6) 26 (65.0) 21 (55.3) 49 (62.0) 51 (54.8) 222 (64.9)
Grade 2 (moderate) 0 4 (14.8) 9 (18.4) 12 (30.0) 10 (26.3) 18 (22.8) 29 (31.2) 82 (24.0)
Grade 3 (severe) 0 2 (7.4) 2 (4.0) 2 (5.0) 7 (18.4) 12 (15.2) 13 (14.0) 38 (11.1)
Subtotal
y
64 159 240 151 160 218 157 1149
Use antihypertensive drugs 1 2 10 25 58 94 85 275
Grade 1 blood pressure (BP) indicates 140±159 mmHg systolic blood pressure (SBP) or 90±99 mmHg diastolic blood pressure (DBP); Grade 2, 160±179 mmHg
SBP or 100±109 mmHg DBP; Grade 3, > 180 mmHg SBP or > 110 mmHg DBP. P , 0.001 for all differences.
y
Excludes those reporting treatment with
antihypertensive drugs.
Table 4. Prevalence of isolated systolic hypertension by age and sex group (%)

Age group Men Women All
18±24 2.00 0.78 1.31
25±34 2.01 2.05 0.46 0.63 1.25 1.36
35±44 1.23 0.18 0.71
45±54 3.72 2.21 3.14
55±64 5.18 7.14 5.70
65±74 14.75 10.56
y
9.09 11.92
y
12.4 11.13
75±92 13.25 18.1 15.9
Crude prevalence
§
4.92 3.64 4.33
Isolated systolic hypertension (ISH), diastolic blood pressure (DBP) , 90 mmHg and SBP > 140 mmHg.
y
No gender difference in the
prevalence of ISH was found in population aged more than 55 years (P  0.512).
§
Crude prevalence was different between men and
women, but not signi®cant (P , 0.051).
Table 5 Hypertension prevalence, awareness, treatment and control in men and women
Men Women All P
Prevalence 946/2278 (41.5%) 478/1948 (24.5%) 1424/4226 (33.7%) , 0.001
Awareness 190/946 (20.1%) 160/478 (33.5%) 350/1424 (24.6%) , 0.001
Treatment 139/190 (73.2%) 136/160 (85.0%) 275/350 (78.6%) , 0.01
Control 29/139 (20.9%) 38/136 (27.9%) 67/275 (24.3%) NS
Awareness, the number of hypertensive persons who were diagnosed before; Treatment, the number of
hypertensive persons who uses anti-hypertension drugs; Control, the number of persons who keep blood

pressure normal (diastolic blood pressure , 90 mmHg and systolic blood pressure , 140 mmHg) among
treatments. NS, not signi®cant (P  0.354).
Hypertension in Korea Jo et al. 1527
other countries, however, the prevalence of hyper-
tension was also reported to be higher than that in the
present data [25±27]. These differences may re¯ect the
effects of dynamic interactions between genetic, socio-
cultural, demographic and economic factors. From this
point of view, each country's own data should be of
great importance to later develop a hypertension sur-
veillance system at the global level. The prevalence of
hypertension shown in this study was comparable to
those from National Health and Nutrition Examination
Survey (NHANES) I [7], western India [9], and south-
eastern Spain [28]. In Korea, however, earlier surveys
reported signi®cantly lower prevalence [15±17], sug-
gesting an upward trend in the prevalence of hyper-
tension for 1990±1992 in Korea. A similar trend was
observed in the prevalence of hypertension in China
during 1980±1991 [23]. In comparison, a signi®cant
downward trend in mean systolic BP and in the
prevalence of hypertension was detected in US [7]
during 1960±1991 and Finland [26] during 1982±1997.
The differences in trends among these are of great
importance, but yet to be fully understood. One
possible explanation is that highly developed countries
have already provided good surveillance systems to
control and prevent high BP, while Korea is only
currently initiating one.
An interesting ®nding of the present study is that the

prevalence of hypertension in men is signi®cantly
(P , 0.001) higher than in women, as shown in Table
Table 6 Prevalence of risk factors of hypertension in men and women
Ã
Men Women
Hypertensive Normotensive Hypertensive Normotensive
Risk factors (n  946) (n  1332) (n  478) (n  1470)
Age (years) 51.7 Æ 17.4 42.8 Æ 16.1 62.2 Æ 17.6 38.1 Æ 14.6
Age group
18±24 4 (24.5%) 151 16 (6.2%) 242
25±34 134 (29.9%) 314 27 (6.2%) 407
35±44 197 (34.6%) 372 53 (9.5%) 502
45±54 126 (42.6%) 170 50 (27.6%) 131
55±64 157 (50.8%) 152 61 (54.5%) 51
65±74 185 (60.7%) 120 127 (57.7%) 93
75±92 98 (64.9%) 53 144 (76.6%) 44
BMI (kg/m
2
) 23.8 Æ 2.86 22.6 Æ 2.72 23.5 Æ 3.72 21.9 Æ 3.05
BMI group
, 20 81 (27.1%) 218 82 (16.1%) 428
20±22 179 (32.7%) 369 95 (19.0%) 404
22±24 246 (40.9%) 355 112 (25.1%) 334
24±26 241 (47.4%) 268 74 (30.0%) 173
26±28 130 (61.3%) 82 56 (42.4%) 76
> 28 69 (63.3%) 40 59 (51.8%) 55
Abdomen circumference (cm) 90.6 Æ 8.78 84.9 Æ 8.40 91.1 Æ 11.9 80.1 Æ 10.2
Years of education
y
< 12 years 715 (43.3%) 935 452 (27.0%) 1221

. 12 years 231 (36.8%) 397 26 (9.45%) 249
Marital status
Single 753 (44.0%) 958 240 (18.8%) 1039
Couple 193 (34.0%) 374 238 (35.6%) 431
Occupation
With 675 (38.0%) 1100 187 (12.9%) 1259
Without 271 (53.9%) 232 291 (58.0%) 211
Driving
Yes 508 (37.1%) 862 43 (10.9%) 351
No 438 (48.2%) 470 435 (28.0%) 1119
Alcohol intakeé6
Yes 630 (42.3%) 860 111 (17.1%) 537
No 316 (40.1%) 472 367 (28.2%) 933
Smoking status
Current smoker 518 (39.6%) 790 44 (37.9%) 72
Ex-smoker 177 (49.0%) 184 5 (31.3%) 11
Nonsmoker 251 (41.2%) 358 429 (23.6%) 1387
Household income (US$/
month)
, 850 398 (47.6%) 438 252 (40.2%) 375
850±1700 347 (38.2%) 561 165 (20.7%) 632
1700±2550 127 (38.4%) 204 50 (13.9%) 310
> 2550 [1] 74 (36.5%) 129 11 (6.7%) 153
Ã
Distributions of hypertensives and normotensives in both genders were signi®cantly different (P , 0.001) by all variables except
years of education and alcohol intake.
y
Men, P , 0.05; women, P , 0.01.
§
Men, not signi®cant; women, P , 0.01.

1528 Journal of Hypertension 2001, Vol 19 No 9
2, which contributed to high overall prevalence. It is
interesting, but not totally new, since Jee et al. [16] have
already reported that the prevalence of hypertension
was 28.9% in Korean men and 15.9% in Korean women.
Furthermore, an interesting result when working on a
Bulgarian population study, showed a signi®cantly high-
er prevalence of age-adjusted hypertension in men
(59.1%) than that in women (36.2%) (P , 0.001) [14].
The reasons for these large gender differences resulting
from the present study have not been determined with
certainty to date. One possible explanation is that the
men had a higher BMI and greater abdomen circumfer-
ence as shown in Table 1, which can contribute to
higher prevalence of hypertension. Despite the signi®-
cant gender difference of overall hypertension preva-
lence, the general pattern of an increasing average
systolic BP has been recognized as in previous studies
(Fig. 2) [8,14]. Also, the pattern of the age-related
increase in diastolic BP followed by a plateau from
middle-age has been the norm in most surveys, [14].
The prevalence of hypertension classi®ed by severity
was dramatically changed by age (Table 3). For exam-
ple, between 65 and 74 years of age, 56.1% of men had
Grade 1; 28.8% Grade 2; 15.1% Grade 3, whereas
62.0% of women had Grade 1; 22.8% Grade 2; 15.2%
Table 7 Odds ratio of various risk factors for hypertension in men and women
Men Women
Risk factors Odds ratio (CI)
Age-adjusted

odds ratio (CI) Odds ratio (CI)
Age-adjusted odds
ratio (CI)
Age (years)
18±24 1 1
25±34 1.32 (0.90±1.92) 1.00 (0.53±1.90)
35±44 1.63 (1.13±2.35)
ÃÃÃ
,
} 1.60 (0.89±2.85)
45±54 2.28 (1.54±3.39)
ÃÃÃ
5.78 (3.16±10.5)
ÃÃÃ
55±64 3.18 (2.15±4.71)
ÃÃÃ
18.1 (9.66±33.9)
ÃÃÃ
65±74 4.75 (3.20±7.06)
ÃÃÃ
20.6 (11.7±36.6)
ÃÃÃ
75±84 5.70 (3.58±9.06)
ÃÃÃ
± 49.5 (26.9±90.9)
ÃÃÃ
±
BMI (kg/m)
, 20 1111
20±22 1.31 (0.96±1.78) 1.61 (1.16±2.23)

ÃÃ
1.23 (0.89±1.70) 1.12 (0.75±1.66)
22±24 1.87 (1.38±2.52)
ÃÃÃ
2.15 (1.57±2.95)
ÃÃÃ
1.75 (1.27±2.41)
ÃÃÃ
1.38 (0.94±2.03)
24±26 2.42 (1.78±3.30)
ÃÃÃ
2.75 (1.99±3.80)
ÃÃÃ
2.23 (1.56±3.20)
ÃÃÃ
1.26 (0.82±1.94)
26±28 4.27 (2.93±6.22)
ÃÃÃ
4.98 (3.37±7.37)
ÃÃÃ
3.85 (2.53±5.84)
ÃÃÃ
1.87 (1.13±3.09)
ÃÃ
> 28 4.64 (2.92±7.40)
ÃÃÃ
5.32 (3.28±8.61)
ÃÃÃ
5.60 (3.62±8.67)
ÃÃÃ

2.35 (1.40±3.92)
ÃÃÃ
Abdomen circumference (cm)
< 75 1111
75±80 1.86 (1.22±2.84)
ÃÃÃ
1.62 (1.05±2.49)
Ã
2.13 (1.40±3.26)
ÃÃÃ
1.37 (0.86±2.17)
80±85 2.24 (1.51±3.32)
ÃÃÃ
1.80 (1.20±2.68)
ÃÃ
3.18 (2.13±4.74)
ÃÃÃ
1.52 (0.97±2.37)
85±90 2.84 (1.93±4.19)
ÃÃÃ
2.14 (1.44±3.19)
ÃÃÃ
3.99 (2.68±5.94)
ÃÃÃ
1.12 (0.70±1.78)
90±95 5.84 (3.94±8.67)
ÃÃÃ
4.04 (2.69±6.08)
ÃÃÃ
6.27 (4.12±9.55)

ÃÃÃ
1.51 (0.92±2.47)
95±100 7.39 (4.83±11.3)
ÃÃÃ
5.01 (3.23±7.77)
ÃÃÃ
14.8 (9.50±23.1)
ÃÃÃ
2.72 (1.61±4.59)
ÃÃÃ
. 100 10.6 (6.62±17.0)
ÃÃÃ
6.90 (4.24±11.2)
ÃÃÃ
21.3 (13.7±33.2)
ÃÃÃ
3.12 (1.85±5.28)
ÃÃÃ
Years of education
< 12 years 1111
. 12 years 0.76 (0.63±0.92)
ÃÃ
1.02 (0.83±1.24) 0.28 (0.19±0.43)
ÃÃÃ
0.82 (0.52±1.30)
Marital status
Single 1111
Couple 0.66 (0.54±0.80)
ÃÃÃ
0.98 (0.79±1.22) 2.39 (1.94±2.95)

ÃÃÃ
1.24 (0.93±1.64)
Occupation
With 1111
Without 1.94 (1.56±2.33)
ÃÃÃ
1.00 (0.79±1.28) 9.28 (7.34±11.7)
ÃÃÃ
1.56 (1.08±2.25)
ÃÃ
Driving
Yes 1111
No 1.58 (1.33±1.88)
ÃÃÃ
1.01 (0.83± 1.23) 3.17 (2.27±4.44)
ÃÃÃ
1.31 (0.90±1.90)
Household income ($US/month)
, 850 1111
850±1700 0.39 (0.31±0.49)
ÃÃÃ
0.85 (0.63±1.14) 0.39 (0.31±0.49)
ÃÃÃ
0.84 (0.63±1.14)
1700±2550 0.24 (1.71±0.34)
ÃÃÃ
0.92 (0.62±1.38) 0.24 (0.17±0.34)
ÃÃÃ
0.91 (0.61±1.36)
> 2550 0.11 (0.06±0.20)

ÃÃÃ
0.42 (0.21±0.82)
ÃÃ
0.11 (0.06±0.20)
ÃÃÃ
0.41 (0.21±0.81)
ÃÃ
Alcohol intake
No 1111
Yes 1.09 (0.92±1.30) 1.34 (1.11±1.61)
ÃÃ
0.52 (0.41±0.67)
ÃÃÃ
1.23 (0.92±1.66)
Smoking status
Nonsmoker 1111
Current smoker 0.94 (0.77±1.14) 0.96 (0.78±1.18) 1.98 (1.34±2.92)
ÃÃÃ
0.98 (0.59±1.62)
Ex-smoker 1.37 (0.06±1.78)
Ã
1.05 (0.80±1.39) 1.47 (0.51±4.25) 0.44 (0.12±1.52)
CI, con®dence interval; BMI, body mass index.
§,Ã
P , 0.05,
ÃÃ
P , 0.01,
ÃÃÃ
P , 0.001.
Hypertension in Korea Jo et al. 1529

Grade 3. To what extent well-established risk factors
for hypertension, such as BMI, years of education,
occupation, alcohol intake and smoking, account for the
observed age-speci®c variation in hypertension severity
is an important issue worthy of further investigation.
As shown in Table 4, ISH was not common (1.36%) in
the population aged , 54 years, while its prevalence
greatly increased (11.13%) in the elderly (. 55 years).
This result supported again that ISH is the most
common form of hypertension in the elderly [29,30].
The prevalence of ISH in the elderly Korean could not
be directly compared with other previous ®ndings,
since each study employed different de®nitions (diasto-
lic and systolic cut-off points) and age distribution of
the population studied. Several other factors besides
de®nitions and age group studied were gender, social
class, the number of blood pressure readings performed,
geographical location, and treatment status [30,31].
Because of these limitations, the prevalence of ISH
varied from study to study; ranged from 1% in Israel to
24% in Norway when the criterion of ISH de®ned as a
systolic BP > 160 mmHg and diastolic BP , 90 or
95 mmHg was used [31]. When the lowest limit of
systolic BP was adjusted as 140 mmHg, the prevalence
of ISH in the elderly Korean was comparable to that
from the 1992±1993 Mexican study [32]. Furthermore,
it was also found to be signi®cantly lower than those in
the studies by Multiple Risk Factor Intervention Trial
Research Group [33], Psaty et al. [34], and Kocemba et
al. [35]. Despite signi®cantly lower prevalence from

this study, however, it is likely that ISH will become a
truly major medical and social problem since popula-
tions in Korea are becoming older. Insigni®cant or less
gender difference in the prevalence of ISH in the
elderly Korean may re¯ect the fact that ISH is primarily
a characteristic of older ages at a time when the male
and female systolic pressure difference is minimal or
reversed [36].
Although 33.7% of the total population were hyper-
tensive, only one-quarter (24.6%) of hypertensive in-
dividuals were aware of their condition (Table 5). This
low rate of awareness is somewhat unexpected, since
Korean National Health Insurance Policy has provided
most Koreans with medical examinations including BP
measurement, every other year. This suggested, in part,
delinquent measurement of hypertension during exam-
ination. As much as 65% awareness was reported from
the population-based study in Barbados [37]. A recent
study in Austria advised improved strategies to achieve
better community control of hypertension since they
found that the intensive blood pressure education
campaign had only a temporary effect on improving
blood pressure awareness [38].
Despite the low rate of awareness in Korea, the diag-
nosis of hypertension led to medical treatment in about
three-quarters (78.6%) of patients. This is not surpris-
ing, since hypertensive patients were within easy access
of inexpensive antihypertensive medication in Korea.
Contrary to treatment, the control of hypertension by
antihypertensive drug therapy was rather low, with only

one-quarter (24.3%) of treated patients achieving an
adequate BP control. One possible explanation might
be a lack of aggressiveness in treating the patients [39].
Another accepted reason for not achieving goal BP is
poor patient compliance with the antihypertensive
medication. According to many studies, only 50±60% of
patients adhere well to the prescribed medication
[40,41]. It has been suggested that interventions fo-
cused on better patient compliance should be persona-
lized and multifactorial, but no detailed studies are so
far available [42]. The other possible reason may be the
side-effects of the antihypertensive drugs currently
available. The low ef®cacy of antihypertensive treat-
ment in the community raises an important question of
its cost-effectiveness. Indeed, an ineffective treatment
will greatly increase the costs induced by the diseases
related to hypertension (stroke and coronary heart
diseases). The impact on health expenditure of the
failure to adequately control BP by drug treatment
should thus be considerable.
A signi®cantly higher rate of awareness, treatment and
control was prominent in women as shown in Table 5.
Since men usually could afford to have systematic
clinical examinations, it was assumed that the levels of
hypertension awareness, treatment and control rates
were relatively higher in men than in women. Interest-
ingly, however, the results from the present study
showed that women achieved better awareness, treat-
ment and control than men. The reason for this result
is yet to be fully understood. Another interesting ®nd-

ing in the present study is the signi®cant deviation
from classical `rule of halves', which is currently con-
troversial, to be applied [43].
Table 8 Multivariate logistic regression analysis for association of
various risk factors with prevalence of hypertension in Ansan-city,
Korea
Men Women
Odds ratio (CI) Odds ratio (CI)
Age 1.26 (1.17±1.37)
ÃÃÃ
,§
1.81 (1.62±2.03)
ÃÃÃ
BMI 1.18 (1.08±1.30)
ÃÃ
1.09 (0.98±1.21)
Abdomen
circumference 1.27 (1.17±1.37)
ÃÃÃ
1.13 (1.03±1.23)
Ã
Years of education 0.97 (0.78±1.21) 0.97 (0.61±1.55)
Marital status 1.16 (0.90±1.48) 1.15 (0.84±1.58)
Occupation 1.08 (0.84±1.48) 1.34 (0.89±2.01)
Household income 1.02 (0.91±1.13) 0.88 (0.74±1.03)
Driving 1.20 (0.96±1.50) 1.16 (0.79±1.70)
Alcohol intake 1.32 (1.08±1.61)
ÃÃ
1.23 (0.91±1.66)
Smoking status 0.94 (0.85±1.05) 0.98 (0.76±1.26)

CI, con®dence interval; BMI, body mass index.
§,Ã
P , 0.05,
ÃÃ
P , 0.01,
ÃÃÃ
P , 0.001.
1530 Journal of Hypertension 2001, Vol 19 No 9
Studies from developing and developed countries have
shown that obesity [9,44±46], smoking [9,46], alcohol
intake [18,46], and years of education [47±49] are
associated with the prevalence of hypertension. The
present data are in accord with an association of
smoking, obesity and less years of education with
hypertension in both genders, but an association of
alcohol intake only in women (Table 6). However, age-
adjustment nulli®ed the signi®cant associations of years
of education, marital status, driving, and smoking with
hypertension (Table 7). It is dif®cult to understand
why our data showed no signi®cant association between
smoking and age-adjusted hypertension in both gen-
ders. Since smoking, a well-known risk factor for hyper-
tension [9,46], is relatively popular in Korea, more
detailed studies should be awaited for con®rmation of
this data. Both non-working women and alcohol con-
suming males had signi®cant positive associations with
age-adjusted hypertension in this study (P , 0.01). The
signi®cant, but negative association of highest house-
hold income (> US$2550/month) with age-adjusted
prevalence of hypertension in both genders re¯ects that

individuals from high socio-economic status are likely
to prevent or control hypertension. This ®nding is
consistent with observations made in developed coun-
tries [50,51]. The association of diabetes mellitus with
hypertension is well known [46], and should be consid-
ered as a risk factor in the study. However, only 14
individuals from the study population (n  4226) re-
ported their history in self-administered questionnaires,
and therefore may be considerably underdetected.
Therefore we did not analyse this variable in the
current study. Obese persons are prone to develop
hypertension and the present data showing the strong
dose±response relationship between BMI and hyper-
tension con®rm this association. Average BMI index
(23.8 kg/m
2
for men; 23.5 kg/m
2
for women) observed
in hypertensives in the present study is usually consid-
ered within desirable limits in developed countries
[52], therefore, lifestyle guidelines for the hypertension
prevention in Korea should be different from those
developed countries. The limit of BMI index (22.6 kg/
m
2
for men; 21.9 kg/m
2
for women) observed in normo-
tensives in this study may be given due consideration

to de®ne safe limits for the risk factor for the preven-
tion of hypertension in Korean. Although many risk
factors are to be considered, our data clearly indicated
that BMI and abdomen circumference are independent
and preventable predictors of hypertension in Koreans,
although slightly less signi®cant in women (Table 8).
Therefore, it is widely recognized that the future
programmes for the primary prevention of hypertension
should concentrate on obesity in Korea.
In summary, the results from the present Ansan study
show a higher prevalence of hypertension than has
been reported in previous Korean studies. Our ®ndings
also suggest strong associations between hypertension
and BMI and abdomen circumference. There was no
signi®cant relationship between hypertension and
smoking and this remains to be further studied. The
extremely high prevalence of hypertension coupled
with the disturbingly low prevalence rates of awareness
and control has important implications for health care
providers, public health of®cials, and health policy-
makers in Korea. This study identi®es an urgent need
for nationwide efforts to prevent and control hyper-
tension, in order to avert an epidemic of BP-related
atherosclerotic cardiovascular diseases.
Acknowledgements
We thank Drs Namhan Cho and Sangmee Ahn Jo for
their critical readings, Ms Sun Mi Lee for project
coordination, and Ms Jooyoung Lee for secretarial
assistance. The opinions expressed in this article are
those of the authors and do not necessarily imply

endorsement by his or her employer or the funding
agency.
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