Identification of Normal Blood Pressure in Different Age Group

Abstract

The concept of using single criterion of normal blood pressure with systolic blood pressure (SBP) < 140 mmHg and diastolic blood pressure (DBP) < 90 mmHg for all ages is still disputable. The aim of the study is to identify the cutoff value of normotension in different age and sex groups.
Totally, 127,922 (63,724 men and 64,198 women) were enrolled for the analysis. Finally, four fifths of them were randomly selected as the study group and the other one fifths as the validation group. Due the tight relationship with comorbidities from cardiovascular disease (CVD), metabolic syndrome (MetS) was used as a surrogate to replace the actual cardiovascular outcomes in the younger subjects.
For SBP, MetS predicted by our equation had a sensitivity of 55% and specificity of 67% in males and 65%, 83% in females, respectively. At the same time, they are 61%, 73% in males and 73%, 86% in females for DBP, respectively. These sensitivity, specificity, odds ratio, and area under the receiver operating characteristic curve from our equations are all better than those derived from the criteria of 140/90 or 130/85 mmHg in both genders.
By using the presence of MetS as the surrogate of CVD, the regression equations between SBP, DBP, and age were built in both genders. These new criteria are proved to have better sensitivity and specificity for MetS than either 140/90 or 130/85 mmHg. These simple equations should be used in clinical settings for early prevention of CVD.

Full text

Identification of Normal Blood Pressure
in Different Age Group
Jiunn-Diann Lin, Yen-Lin Chen, Chung-Ze Wu, Chang-Hsun Hsieh, Dee Pei,
Yao-Jen Liang, and Jin-Biou Chang
Abstract: The concept of using single criterion of normal blood
pressure with systolic blood pressure (SBP) <140 mmHg and diastolic
blood pressure (DBP) <90 mmHg for all ages is still disputable. The
aim of the study is to identify the cutoff value of normotension in
different age and sex groups.
Totally, 127,922 (63,724 men and 64,198 women) were enrolled for
the analysis. Finally, four fifths of them were randomly selected as the
study group and the other one fifths as the validation group. Due the tight
relationship with comorbidities from cardiovascular disease (CVD),
metabolic syndrome (MetS) was used as a surrogate to replace the actual
cardiovascular outcomes in the younger subjects.
For SBP, MetS predicted by our equation had a sensitivity of 55%
and specificity of 67% in males and 65%, 83% in females, respectively.
At the same time, they are 61%, 73% in males and 73%, 86% in females
for DBP, respectively. These sensitivity, specificity, odds ratio, and area
under the receiver operating characteristic curve from our equations are
all better than those derived from the criteria of 140/90 or 130/85 mmHg
in both genders.
By using the presence of MetS asthe surrogate of CVD, the regression
equations between SBP, DBP, and age were built in both genders. These
new criteria are proved to have better sensitivity and specificity for MetS
than either 140/90 or 130/85mmHg. These simple equations should be
used in clinical settings for early prevention of CVD.
(Medicine 95(14):e3188)
Abbreviations: BP = blood pressure, CVD = cardiovascular
disease, DBP = diastolic blood pressure, FPG = fasting plasma
glucose, JNC = Joint National committee on Detection Evaluation
and Treatment of High Blood Pressure, ROC = receiver operating
characteristic, MetS = metabolic syndrome, SBP = systolic blood
pressure, TG = triglyceride.
INTRODUCTION
It is well-known that high blood pressure (BP) is the funda-
mental cause for many serious cardiovascular diseases (CVD)
such as cerebral vascular disease and coronary artery disease.
1
Several reports have shown that there is a continuous, graded,
and strong relationships between BP and the risk CVD.
2,3
The definition of normal BP (systolic blood pressure
[SBP] <140 mmHg and diastolic blood pressure
[DBP] <90 mmHg) was first proposed by the 3rd report of Joint
National committee on Detection, Evaluation and Treatment of
High Blood Pressure in 1984 (JNC III).
4
However, some of the
researchers are still skeptical about this criteria. For example,
Domanski et al
5
suggested that the cardiovascular mortality could
be avoided by lowering the BP down to 120/80 mmHg in both
younger and middle-aged group based on data from a 22 years
follow-up cohort (Multiple Intervention Trial cohort). Further-
more, by using logistic splines analytic method, Port et al
6
also
suggested that hypertension should be defined according to age-
and sex-specific threshold rather than a single value. At the same
time, one of the largest meta-analysis including 61 cohorts,
958,074 subjects, and 56,000 cardiovascular deathsalso indicated
a different value of optimal BP which is 115/75 mmHg.
7
The
results of these important studies indicated that the definition of
normal BP is still under controversial.
The clustering of hypertension, dyslipidemia, and obesity
have been noted early in 2001.
8
As they are highly correlated to
future occurring of the CVD and diabetes, the World Health
Organization has denoted this phenomenon as metabolic syn-
drome (MetS) in 1998.
9
Later, a modified and simpler version
published by the National Cholesterol Education Program in
2002.
10
By far, this is the most widely accepted and used
criteria. It should be stressed that the original purpose to define
MetS was trying to early detect subjects with high risk for CVD
and diabetes. Till now, compiling results derived either in the
cross-sectional or the longitudinal studies all repeatedly vali-
dated its predictability. Noticeably, in most of these pivotal
studies, actual occurrences of mortality and/or morbidities were
often used as the primary endpoints. It is not difficult to
postulate that these endpoints are common in the elderly.
However, in the younger cohort, these cardiovascular outcomes
are much less to be found. To have enough number for an
observational study to become statistically significant would
take a long time which is difficult for many of the researchers.
Unfortunately, the aforementioned definition for normotension
derived from older cohort is being applied to all age groups at
Editor: Miguel Camafort-Babkowski.
Received: October 23, 2015; revised: February 26, 2016; accepted: March
3, 2016.
From the Department of Internal Medicine, School of Medicine, College of
Medicine, Taipei Medical University, Taipei, Taiwan (J-DL, C-ZW);
Division of Endocrinology and Metabolism, Department of Internal
Medicine, Shuang Ho Hospital, Taipei Medical University, New Taipei
City, Taiwan (J-DL, C-ZW); Department of Pathology, Cardinal Tien
Hospital, School of Medicine, Fu-Jen Catholic University, New Taipei (Y-
LC); Division of Endocrinology and Metabolism, Department of Internal
Medicine, Tri-Service General Hospital, National Defense Medical School,
Taipei (C-HH); Department of Internal Medicine, Cardinal Tien Hospital,
School of Medicine, Fu-Jen Catholic University, New Taipei (DP);
Associate Dean of College of Science and Engineering, Director of
Graduate Institute of Applied Science and Engineering, Department and
Institute of Life-Science, Fu-Jen Catholic University, New Taipei (Y-JL);
and Department of Pathology, National Defense Medical Center, Division
of Clinical Pathology, Tri-Service General Hospital, Taipei, Taiwan ROC
(J-BC).
Correspondence: Jin-Biou Chang, Department of Pathology, National
Defense Medical Center, Division of Clinical Pathology, Tri-Service
General Hospital. No 325, Sec 2, Cheng-Kung Road, Nei-Hu, Taipei,
Taiwan ROC (e-mail: jinbiou@gmail.com).
The authors have no funding and conflicts of interest to disclose.
Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved.
This is an open access article distributed under the Creative Commons
Attribution-NonCommercial-NoDerivatives License 4.0, where it is
permissible to download, share and reproduce the work in any medium,
provided it is properly cited. The work cannot be changed in any way or
used commercially.
ISSN: 0025-7974
DOI: 10.1097/MD.0000000000003188
Medicine®
OBSERVATIONAL STUDY
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present, and it is easily to understand that this is just not
reasonable. Ever since the publication of the notion of MetS,
there are many longitudinal studies focusing on its predictable
CVD.
11–13
These studies unanimously showed positive results
and were published in some of the best journals. Thus,
MetS could be used as a surrogate to replace the actual
cardiovascular outcomes in the younger subjects. Although
it is less accurate, by using this method, we could re-evaluate
the more logical cutoff points of normotension in the younger
population.
Other than this, it is also important to note that both SBP
and DBP change as age increases.
14
In other words, age plays a
very important role in the regulation of BP. Therefore,
we hypothesized that the definition for normal SBP and
DBP should vary rather than using the same value in all
age-groups.
In this cross-sectional study, we enrolled 127,922 subjects.
Four fifths of the subjects were used to build an equation from
the logistic regression lines of SBP and DBP to have MetS in
different gender. The levels of BP calculated from these curves
could detect either CVD or diabetes more precisely and should
be regarded as the definition of hypertension in its correspond-
ing age and sex groups. Finally, these equations are further
verified and compared with the present standard of normal BP
in the remaining one fifths of the subjects.
MATERIALS AND METHODS
Study Population
The study subjects of the present study were enrolled form
the data bank of Meei-Jaw (MJ) Health Screening Centers
between 1999 and 2008. MJ health screening centers are
privately owned chain of outpatient department located
throughout the whole Taiwan, which offer routine health check-
ups. Therefore, the database contained subjects everywhere in
Taiwan. All study subjects were anonymous, and informed
consent was obtained from each participant. The study proposal
was reviewed by the institutional review board of MJ Health
Screening. Totally, 129,680 subjects were enrolled when under-
going routine health checkups. They were between 21 and
65 years old. Since BP was the major variables we
evaluated in this study, subjects who taking any medications
would influence BP were excluded. Finally, 127,922 (63,724
men and 64,198 women) were eligible for the analysis. Four
fifths of them were randomly selected as the study group and the
other one fifths as the validation group. Reporting of this study
conforms to the STROBE statement along with references to the
STROBE statement and the guidelines.
Anthropometric Measurements and General
Data
The participant’s medical history, including present medi-
cations, was acquired by the study nurses using a questionnaire.
Detailed physical examinations were done for each subject. An
auto-anthropometer Nakamura KN-5000A (Nakamura, Tokyo,
Japan) was used to determine body weight and height. Waist
circumference was measured at the midpoint between the
inferior border of the last rib and the iliac crest in a horizontal
level. A computerized auto-mercury-sphygmomanometer,
Citizen CH-5000 (Citizen, Tokyo, Japan) was used to measure
BP on the right arm of each subject seated, after 5 minutes of
rest. BP was measured twice at 10-min intervals. The average
value of these 2 records was taken into the analysis.
Laboratory Evaluation
After the 10 hour overnight fast, blood specimens were
collected from each subject for further analysis. Plasma was
separated from the whole blood within 1 hour and stored at
70 8C. Fasting plasma glucose (FPG) and plasma lipid con-
centrations were measured later. A glucose oxidase method
(YSI 203 glucose analyzer; Scientific Division, Yellow Springs
Instruments, Yellow Springs, OH) was used to determine FPG
levels. The dry, multilayer analytical slide method in the Fuji
Dri-Chem 3000 analyzer (Fuji Photo Film, Minato-Ku, Tokyo,
Japan), was used to determine total cholesterol and triglyceride
(TG). An enzymatic cholesterol assay following dextran sulfate
precipitation was used to determine serum high-density lipo-
protein cholesterol and low-density lipoprotein cholesterol
levels.
Definition of Metabolic Syndrome
We used the newest criteria of MetS in 2009 with some
revision.
15
The WC more than or equal to 90 and 80 cm in
Taiwanese men and women, respectively.
16
Other 4 criteria
were the same: SBP more than or equal to 130 mmHg or DBP
more than or equal to 85 mmHg, TG more than or equal to
150 mg/dL, FPG more than or equal to 100 mg/dL, and HDL
less than or equal to 40 and 50 mg/dL in men and women or
taking related medications.
In the present study, the BP was the independent com-
ponent. Thus, subjects with any 2 of remaining 4 MetS com-
ponents were regarded as fulfilling the diagnosis of MetS. Other
than the National Cholesterol Education Program hypertension
criteria, the JNC VII definition (140/90 mmHg) was also used
for the comparison.
Statistical Analysis
Subjects in the study group were stratified by the age
interval (every 5-year old) in both men and women. From 21 to
65 years old, 9 age groups were obtained. There are 2 parts of
the analysis. The purpose of the 1st one is to build the equations
which could be used to identify the cutoff values for MetS. In
the study group, whether the participants having MetS or not (0
or 1) was regarded as the dependent variable. At the same time,
SBP or DBP was the independent variable. By using the logistic
regression and receiver operation curve, cutoff values for SBP
and DBP were determined in each age group. Subjects with
higher BP than these cutoff values would have a higher chance
to have MetS. Then, the cutoff points of each 5-year age group
were plotted against age for SBP and DBP in a scatter graph
separately (y- and x-axis, respectively). A fitted line was
determined by regression analysis and, finally, a corresponding
equation was obtained for either SBP or DBP in women and
men separately. In the 2nd part, our purpose was to validate the
proposed new criteria derived from the equations. Basically,
the ages of the participants were put into the equations which are
sex-specific and then the estimated criteria for normal BP would
be obtained accordingly. Afterwards, we compared the JNC VII
(140/90 mmHg) and MetS criteria (130/85 mmHg) against ours
for predicting having MetS.
15,17
To fulfill this purpose, in the
validation group, subjects were divided into normotensive and
hypertensive according to the 3 different definitions. This is
regarded as the independent variable. Then, whether having
MetS is taken as the dependent variable in logistic regression
model. The area under receiver operating characteristic (ROC)
curve derived from these 3 models are compared. The larger the
area, the more accuracy the model is for predicting having
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MetS. In other words, it should be a better definition
for hypertension.
All statistical analyses were performed using SPSS 18.0
software (SPSS Inc., Chicago, IL). The data are presented as the
mean standard deviation unless indicated otherwise. Indepen-
dent t-test was applied to compare the differences between the
study and the external validation groups and between subjects
with and without MetS. The TG level was not normally dis-
tributed and therefore log transformation was performed before
analysis. Logistic regression analysis was used to calculate odds
ratios (ORs) for an increased risk of having MetS.
RESULTS
The demographic data of the study and validation group for
males and females is displayed in Table 1. By the grouping
criteria, it could be expected that there were no significant
difference in demographic and major MetS components
between the 2 groups. However, between subjects with and
without MetS, it could be noted that all the components
were significantly different which is not surprizing. As it is
explained in the method, the cutoff values for proper SBP and
DBP were determined by using the logistic regression and ROC
curve for each 5-year age group. These results are showed in
Table 2. These cutoff points for SBP and DBP in both males and
females were plotted against the age and are showed in Figure 1.
It could be noted that for both genders the SBP concave down a
little bit between 30 and 40 years old. On the other hand, the
curves are quite different for DBP. The line for male is a
sigmoidal curve. Compared to it, the relationship between
age and DBP is a straight line in females. From these lines,
equations were built and then were used in the validation groups
for predicting MetS. The positive predict value, negative predict
value, sensitivity, and specificity of different BP cutoff points
are shown in Table 3. For SBP, MetS predicted by our equation
had a sensitivity of 55% and specificity of 67% in males and
TABLE 1. Demographic Data of the Study and Validation Group
MetS () MetS (þ)P
Study group
Male
n 34840 14617
Age, years 46.3 11.4 47.3 9.4 <0.001
Body mass index, kg/m
2
23.6 3.2 23.8 3.0 <0.001
Systolic blood pressure, mmHg 119.9 15.9 122.8 14.1 <0.001
Diastolic blood pressure, mmHg 75.3 10.8 74.3 10.2 <0.001
Fasting plasma glucose, mg/dL 98.4 21.0 94.5 15.6 <0.001
HDL-C, mg/dL 42.4 12.5 43.6 9.3 <0.001
Triglyceride, mg/dL 127.8 73.1 128.0 85.0 <0.001
Female
n 41265 11598
Age, years 45.7 11.7 46.3 9.6 <0.001
Body mass index, kg/m
2
22.3 3.4 22.7 3.2 <0.001
Systolic blood pressure, mmHg 115.6 18.3 113.0 14.8 <0.001
Diastolic blood pressure, mmHg 72.1 10.8 67.3 9.8 <0.001
Fasting plasma glucose, mg/dL 95.3 18.7 90.6 13.3 <0.001
HDL-C, mg/dL 50.6 13.3 53.2 11.9 <0.001
Triglyceride, mg/dL 96.3 54.2 94.5 57.1 <0.001
Validation group
Male
n 8042 6225
Age, years 49.0 9.7 50.0 8.8 <0.001
Body mass index, kg/m
2
23.5 2.5 26.5 2.8 <0.001
Systolic blood pressure, mmHg 120.5 13.5 125.7 14.2 <0.001
Diastolic blood pressure, mmHg 72.6 9.8 76.4 10.3 <0.001
Fasting plasma glucose, mg/dL 90.7 10.5 99.0 19.3 <0.001
HDL-C, mg/dL 47.0 9.0 38.7 6.7 <0.001
Triglyceride, mg/dL 102.3 46.5 184.4 100.7 <0.001
Female
n 8669 2666
Age, years 47.3 9.5 51.9 8.6 <0.001
Body mass index, kg/m
2
21.7 2.4 25.8 3.4 <0.001
Systolic blood pressure, mmHg 110.6 13.6 120.7 15.4 <0.001
Diastolic blood pressure, mmHg 65.9 9.3 71.6 10.0 <0.001
Fasting plasma glucose, mg/dL 87.6 7.7 99.3 21.1 <0.001
HDL-C, mg/dL 55.7 11.4 44.0 7.6 <0.001
Triglyceride, mg/dL 77.6 33.2 149.7 79.1 <0.001
HDL-C ¼high density lipoprotein cholesterol.
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65%, 83% in females, respectively. At the same time, they are
61%, 73% in males and 73%, 86% in females for DBP,
respectively. These sensitivity and specificity are better than
those derived from the criteria of 140/90 or 130/85 mmHg.
Table 4 shows the ORs derived from the logistic regression of
the various criteria of BP predicting MetS. As expected, the ORs
estimated by our equations were better than conventional
normotension criteria in both genders.
Finally, Figure 2 shows the ROC curves of the 3 different
normotension criteria. The areas under ROC from our equations
were unanimously the highest one in either SBP or DBP in both
genders. All of them reached statistical significance.
DISCUSSION
The present criteria of normal BP was first proposed by
JNC III. It was determined according to several large-scale,
prospective, and observational studies by using stroke and
coronary heart disease as the primary end points. However,
the concept of using 1 criterion for all ages is still disputable.
For instance, it is hard to be agreed that a 20-year-old subject
would under the same CVD risks compared to a 65-year-old
subject if they all had a BP of 130/80 mmHg. One may argue
about the justifiability to use MetS as an endpoint for determin-
ing the cutoff values of BP. However, as mentioned earlier in
the introduction, we have several reasons to rationalize this
method. First, the traditional definition of normal BP is derived
from the older subjects. Caution must be taken when exercise
this definition into young adulthoods. Second, it is practically
very difficult to follow a person from young to old age. Before
further longitudinal study by using CVD as the endpoint in
young adults could be done, our results provide a new concept to
define ‘‘normal’’ BP. Third, Ford
11
had published his milestone
study in Diabetes Care by observing all the major longitudinal
studies focusing on the predictability of MetS. Although these
studies used different endpoints (coronary heart disease, myo-
cardial infarction, stroke and diabetes, etc.), the results unan-
imously support the values of MetS. Fourth, it is undoubtable
that each component of MetS is independently related to future
CVD and diabetes. Thus, the collectively correlations of these
components should be better than the single component.
In the present study, equations for SBP and DBP were built
separately in men and women. By putting the ages into these
equations, the levels of normal SBP and DPB for that age will be
calculated. The results of ROC curve showed that our revised
criteria have unanimously higher predictive power for MetS
than that of the traditional criteria in both genders. In other
words, the tradition generalized criteria of hypertension for all
ages are challenged.
Most evidences have shown that SBP increases with age.
However, DBP increases first before 45 years old and then
declines afterwards. The main underlying mechanism of this
age-related changes of BP might be caused by the arterial
stiffness.
14,18– 21
In their longitudinal study, Safar et al
19
found
that the relationships between SBP, DBP, and ages are linear
and curvilinear, respectively, in a healthy population. Similar to
the grouping criteria used in Framingham and Safar’s studies,
we divided our subjects into 5-year-old subgroups. Four
equations were made to define the threshold of BP for having
MetS in both genders. Not surprizingly, as age increases, the
cutoffs of SBP rise in both sexes. In the same time, this linear
relationship was only found in the DBP of females. The curve of
DBP in male is an interesting exception which is a sigmoid line
and has the lowest values between 31 and 40 years old
(75.5 mmHg) and the highest at 46 and 55 (80.5 mmHg). This
finding might be attributed to the interference of some risk
factors other than the MetS components, such as smoking or
low-density lipoprotein cholesterol, which were not analyzed in
the present study. Further well-designed research is needed to
elucidate this issue.
Pathologically, the mechanisms of increased SBP and DBP
in hypertensive patients are not the same. The elevation of SBP
is partly caused by the increased cardiac output, reduced large
arteries compliance and the rise of peripheral resistance.
22,23
However, in the general population, diseases resulting in
increase of the cardiac output, such as anemia, hyperthyroidism
aortic regurgitation, and arteriovenous fistula, etc. are relatively
few. In other words, age-related arterial rigidity and resistance
play the most important role in the ‘‘systolic hypertension.’’
18
As age increases or atherosclerosis advances, the elasticity of
aorta decreases which followed by the increased SBP and
reduced DBP. Interestingly, DBP is considered to be the main
target of treatment for the young people while, in the elderly,
SBP is the goal.
18,20
In this study, we believed that our criteria
are more sensitive for detecting subjects with risks since it is
age- and sex-specific.
It is well-recognized that gender differences in BP starts
since adolescence.
24
After puberty, females generally have
lower BP than males. This difference might be caused by the
higher androgen secretion in males. This hypothesis could be
supported by either the human or the animal studies. For
example, in females with polycystic ovary syndrome, the BP
increases.
25
On the other hand, in castration male rats which
have decreased androgen, the BP parallels with the change of
the hormone.
26
Results of observational studies in human
beings also suggest the protection role of estrogen against
hypertension since higher BP is noted after menopause.
25
However, some reports showed that there was no significant
TABLE 2. Blood Pressure Cutoff Point According to the Age
Strata in Study Group
Age SBP DBP
Male
21– 25 120.5 78.5
26– 30 119.5 76.5
31– 35 114.5 75.5
36– 40 120.5 75.5
41– 45 115.5 78.5
46– 50 119.5 80.5
51– 55 125.5 80.5
56– 60 129.5 79.5
61– 65 143.5 76.5
Female
21– 25 115.5 70.5
26– 30 113.5 71.5
31– 35 110.5 72.5
36– 40 112.5 74.5
41– 45 116.5 73.5
46– 50 124 78.5
51– 55 122.55 74.5
56– 60 132.5 78.5
61– 65 130.5 77.5
DBP ¼diastolic blood pressure, SBP ¼systolic blood pressure.
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FIGURE 1. Equation of the blood pressure according to the cutoff point in different age strata in study group. (A) Male systolic blood
pressure; (B) male diastolic blood pressure; (C) female systolic blood pressure; and (D) female diastolic blood pressure.
TABLE 3. Positive Predict Value, Negative Predict Value, Sensitivity, and Specificity of Different Blood Pressure Cut Point in
Validation Group
PPV, % NPV, % Sensitivity, % Specificity, %
Male
SBP cut point by equation 56 66 55 67
SBP cut point of 130 mmHg 55 61 37 76
SBP cut point of 140 mmHg 60 58 15 92
DBP cut point by equation 64 71 61 73
DBP cut point of 85 mmHg 59 59 20 89
DBP cut point of 80 mmHg 63 58 11 95
Female
SBP cut point by equation 54 89 65 83
SBP cut point of 130 mmHg 47 80 27 91
SBP cut point of 140 mmHg 47 78 10 96
DBP cut point by equation 62 91 73 86
DBP cut point of 85 mmHg 57 78 11 98
DBP cut point of 80 mmHg 53 77 5 99
DBP ¼diastolic blood pressure, SBP ¼systolic blood pressure.
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TABLE 4. Odds Ratio of Different Blood Pressure Cut Point in Validation Group
Odds Ratio (95% Confidence Interval) PValue
Male
SBP cut point by equation 2.350 (2.197– 2.514) <0.001
SBP cut point of 130 mmHg 1.897 (1.766– 2.038) <0.001
SBP cut point of 140 mmHg 2.109 (1.895– 2.346) <0.001
DBP cut point by equation 4.042 (3.769– 4.334) <0.001
DBP cut point of 85 mmHg 2.038 (1.860 – 2.234) <0.001
DBP cut point of 80 mmHg 2.315 (2.037 – 2.630) <0.001
Female
SBP cut point by equation 8.720 (7.923– 9.598) <0.001
SBP cut point of 130 mmHg 3.605 (3.229– 4.025) <0.001
SBP cut point of 140 mmHg 4.745 (3.956– 5.690) <0.001
DBP cut point by equation 15.927 (14.367– 17.656) <0.001
DBP cut point of 85 mmHg 3.105 (2.626 – 3.671) <0.001
DBP cut point of 80 mmHg 3.879 (2.986 – 5.039) <0.001
DBP ¼diastolic blood pressure, SBP ¼systolic blood pressure.
FIGURE 2. Receiver operating characteristic curve of different blood pressure criteria in predicting subjects with 2 or more metabolic
syndrome components in validation group. (A) Male systolic blood pressure; (B) male diastolic blood pressure; (C) female systolic blood
pressure; and (D) female diastolic blood pressure.
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reduction of BP after replacement of estrogen in the menopause
females.
27,28
The discrepancy might be explained by the possib-
ility that the abrupt decline of estrogen in menopause women
might not be the only component responsible for increase of
BP.
27,28
For instance, other than the drop of the estrogen, a mild
decrease of androgen secretion was also noted which could
modulate BP through the rennin-angiotensin-aldosterone sys-
tem and oxidative stress.
29
Because of these aforementioned
reasons, our data highly suggest that the definition of normal BP
should be gender-specific.
To our knowledge, this is the 1st study trying to define
normotension criteria in subjects with different age and genders.
However, there are still some limitations in our study. First, this
is a cross-sectional study which is less powerful. A longitudinal
study may yield more conclusive results. Second, it should be
noted that only Chinese were enrolled in this study. In other
words, it should be exercised with caution when being extrapo-
lated to other ethnic groups.
30
Third, some important confound-
ing factors were not available in the data bank such as exercise
and smoking status and thus could not be adjusted. This would
reduce the reliability of our results. However, because of the
number of cohort is quite substantial, this drawback could
be justified.
In conclusion, by using the presence of MetS as the
surrogate of CVD and diabetes outcomes, the regression
equations between SBP, DBP, and age were built, respectively,
in males and females. All the regression lines are straight
except for the DBP in males. From these equations, cutoff
values for normotension are redefined. By using ROC curves,
these new criteria are proved to have better sensitivity and
specificity for MetS compared to either 140/90 or 130/
85 mmHg. We believe that these simple equations should be
used in clinical settings for early detection of and prevention
of CVD.
ACKNOWLEDGMENTS
The authors thank all participants in the study.
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