Obesity and associated cardiovascular risk factors in iranian children: a cross-sectional study
Pediatrics International (2006) 48, 566–571 Obesity and associated cardiovascular risk factors in Iranian children: A cross-sectional study
ANAHITA HAMIDI , HOSSEIN FAKHRZADEH , ALIREZA MOAYYERI , RASSUL POUREBRAHIM , RAMIN HESHMAT , MASOUMEH NOORI , YALDA REZAEIKHAH AND BAGHER LARIJANI
Endocrinology and Metabolism Research Center, Doctor Shariati Hospital, Tehran University of Medical Science, Tehran, Iran Abstract Background : Obesity is a growing public health problem in developing countries considering its association with cardiovascular risk factors. Relationship between childhood obesity and these risk factors has not been attested in the Iranian population before. The aim of the present study was to investigate frequency of cardiovas- cular risk factors and their association with severity of obesity in a sample of Iranian obese children. Methods : A total of 13 086 children aged 7 – 12 years were screened and those with waist circumference = 90th percentile of their age were invited for further evaluations. Participants were divided into two groups of over- weight or obese according to International Obesity Task Force criteria. Cardiovascular risk factors were defi ned as high fasting total cholesterol, high low density lipoprotein, low high density lipoprotein, high triglycerides, and systolic or diastolic hypertension. These factors were compared between obese and overweight children and their correlations with body mass index and other measures of obesity were tested. Results : Of 532 children (274 boys, mean age 9.5 ± 1.3) enrolled in the study, 194 were overweight and 338 were obese. Mean levels of triglyceride and Apo-lipoprotein B in obese children were signifi cantly higher than overweight participants. A total of 81.9% of obese children and 75.4% of overweight children had at least one cardiovascular risk factor. There were signifi cant correlations between body mass index and systolic blood pres- sure, diastolic blood pressure, serum triglyceride, and Apo-lipoprotein B levels ( P values <0.01). Conclusion : The high prevalence of cardiovascular risk factors in overweight and obese children and positive correlation of these factors with severity of obesity emphasizes the need for prevention and control of childhood obesity from early stages. Key words
cardiovascular risk factors , childhood obesity , dyslipidemia , hypertension , prevention .
Obesity is a growing global epidemic affecting all age groups.
Health Organization Monica Project, over 30% of the people
It is currently regarded as the leading cause of preventable
in the Middle East are overweight. 6 A survey on secondary
death worldwide and escalating obesity would be the greatest
school students in Bahrain revealed that 15.6% of boys and
health threat the world will face in the twenty-fi rst century. 1,2
14.7% of girls were overweight. 7 Like many other countries,
Childhood obesity has also become a major global health con-
the trend for obesity in Iranian children has doubled between
cern in recent decades. 3 It is associated with increasing risk of
atherosclerosis, hyperinsulinemia, hypertension and psycho-
Even in childhood, obesity accompanies other risk factors
social problems in the affected population. 4
for future cardiovascular diseases (CVD), including hyperten-
The prevalence of obesity among children appears to be
sion and dyslipidemia. This set of risk factors has been proved
rising rapidly in developing countries, which could be attrib-
to accelerate progression of atherosclerotic lesions in the cor-
uted to changes in lifestyle. 5 Based on the data of the World
onary arteries of young people. 8 Obese children are at increased risk for adult mortality and morbidity particularly from CVD. 9
Limited number of studies have been performed on child-
Professor Bagher Larijani, Endocrinology and
hood obesity and accompanying cardiovascular risk factors in
Metabolism Research Center, Doctor Shariati Hospital, North
the developing world. For a better understanding on the issue
Kargar Avenue, Tehran 14114, Iran. Email: firstname.lastname@example.org
and more effi cient programs for worldwide prevention of
Received 13 March 2005; revised 25 June 2005; accepted 2
CVD mortality, more ethnic-specifi c studies are needed.
Obesity and cardiovascular risk factors 567
Moreover, the relationship between obesity and other newly
Iran) using automatic serum auto analyzer (Hitachi 902; Boe-
suggested CVD risk factors (such as Apo-lipoprotein A and
hringer Manneheim, Germany). Low Density Lipoprotein
B) is unconfi rmed so far. We aimed in this study to determine
(LDL) cholesterol, High Density Lipoprotein (HDL) choles-
frequency and assortment of these factors and their relation
terol, Apo-lipoprotein A, and Apo-lipoprotein B levels were
with severity of obesity in a sample of primary school Iranian
measured directly by Immunoturbidometric assay (Pars
Azmoon kit; Tehran, Iran). As there is scarce evidence in hand about the borderline cholesterol levels to be considered as nor-mal or risky for children, and considering that all of our par-
ticipants were obese and at-risk children, cut-offs proposed as acceptable by the expert panel of National Cholesterol Educa-
This cross-sectional study was conducted from January to
tion Program on blood cholesterol in children and adolescents
May 2004 in the sixth district of Tehran. We screened 13 089
were used to defi ne normal values. 14 Total cholesterol = 170
pupils aged 7 – 12 years in all of the 65 primary schools of this
mg/dL, LDL =110 mg/dL, HDL < 35 mg/dL, and triglyceride
area. Waist circumference was used as the screening tool to
levels = 150 mg/dL were considered as cardiovascular risk fac-
tors. These four lipid profi le variables and systolic and diasto-
equal or greater than 90th percentile for their ages were invited
lic hypertension comprised six study target variables. The
for further evaluations. A total of 1644 students had high waist
crude values of Apo-lipoproteins A and B were also entered
circumference, of whom 563 subjects attended a school-based
clinic and enrolled in the study. The study protocol was ap-
Pearson correlation test was used to assess the relationships
proved by the ethics committee of Tehran University of
between anthropometric measurements and cardiovascular
Medical Sciences, Tehran, Iran, and written informed consent
risk factors. To control for the possible effects of age and
was obtained from students and their parents.
height on the relationship between BMI and hypertension, par-
Bodyweight was recorded to the nearest 0.5 kilogram (kg)
tial correlation analysis was used. Differences between two
using a standard beam balance scale with the subject barefoot
groups of obese and overweight children were investigated
and wearing light dresses. Body height was recorded to the
nearest 0.5 centimeters (cm) according to the following proto-
necessity of type I error correction for multiple tests used in
col: no shoes, heels together and head touching the ruler with
this study, P values <0.01 were considered as signifi cant.
line of sight aligned horizontally. Body Mass Index (BMI) was calculated as the ratio of body weight (kg) to body height (m) squared. Participants were classifi ed as normal, over-
weight or obese using the international age and gender spe-cifi c BMI cut-offs recommended by the International Obesity
In total, 532 children (274 boys, mean age 9.5 ± 1.3) were en-
Task Force (IOTF). 12 In total, 31 students (5%) were normal
rolled in the study. According to IOTF criteria, 194 participants
were overweight and the other 338 were obese. Anthropometric
Waist circumference was measured to the nearest cen ti-
measurements, blood pressures, and lipid profi les of the study
meter with elastic-band meter with the student in the standing
population are summarized in Table 1. Mean levels of triglyc-
position at the level of the distal third of the distance from the
eride in obese children were signifi cantly higher than over-
xyphoid process to the umbilicus. Hip circumference was
weight group (160.3 ± 46.0 vs 145.0 ± 36.0,
measured 4 cm below the anterior superior iliac spine and
Difference between the two groups regarding Apo-lipoprotein
waist-to-hip ratios (WHR) were calculated as an index of
B was marginally signifi cant ( P = 0.009).
abdominal obesity. One experienced physician measured
As indicated in Table 2, the percentage of participants with
blood pressure using a mercury sphyngmomanometer with a
any of the given risk factors was higher in the obese group. The
cuff size suitable for each subject. Systolic blood pressure
difference between two groups reached a statistical signifi -
(Korotkoff phase I) and diastolic blood pressure (Korotkoff
cance level only for hypertriglyceridemia ( P = 0.003). A total
phase V) were measured twice with a 5 min interval from the
of 18.1% of obese children and 24.6% of overweight children
right arm in supine position and the average of the two meas-
had no cardiovascular risk factor. A total of 12.9% of obese
urements was taken as the student’s blood pressure. We used
children had four or fi ve risk factors, while this fi gure was 8.3%
recommendations of Task Force for High Blood Pressure
for overweight children. The percentages of participants with
in Children and Adolescents to defi ne systolic or diastolic
different numbers of risk factors are schematically presented in
Figures 1 and 2 for different genders. Difference between boys
Overnight fasting venous blood samples were taken from
and girls for none of the risk factors was signifi cant.
the children. Triglyceride and cholesterol levels were meas-
As shown in Table 3, different obesity scales were highly
ured through calorimetric assays (Pars Azmoon kit, Tehran,
correlated with each other. This statement was also correct for
Table 1 Physical and paraclinical characteristics of studied children †
† Data are presented as mean ± standard deviation. HDL, High Density Lipoprotein; LDL, Low Density Lipoprotein.
systolic and diastolic blood pressures as well as different com-
severity of obesity and different cardiovascular risk factors.
ponents of lipid profi le. Correlations between elements of lipid
We observed that about 80% of our obese children are suffer-
profi le and obesity scales reached to statistical signifi cance
ing from at least one established cardiovascular risk factor and
only for triglyceride and Apo-lipoprotein B ( Table 3 ).
these risk factors are interconnected with the severity of obes-
Systolic and diastolic blood pressures were signifi cantly
ity. We found signifi cant correlation between crude measures
correlated with anthropometric variables. The correlation
of obesity (including BMI, waist circumference, and WHR)
between Systolic blood pressure and BMI ( r = 0.297, P <
and systolic and diastolic blood pressures of children. However,
0.001) remained signifi cant after controlling for age ( r = 0.240,
the only elements of lipid profi le that showed a signifi cant cor-
P < 0.001) and height ( r = 0.229, P < 0.001). Partial correla-
relation with obesity measures were serum triglycerides and
tion analysis also showed an independent relationship between
Apo-lipoprotein B. This could have some applications for risk
diastolic blood pressure and BMI controlling for age ( r = 0.193,
assessment of CVD in children and adolescents.
P < 0.001) and height ( r = 0.199, P < 0.001).
The results of our study are consistent with other major
studies that have examined the relationship between obesity and cardiovascular risk factors in children and adolescents. 9,15 – 22
The high prevalence of hypertension in this study is in con-cordance with the results of other studies indicating a strong
This is the fi rst study in Iran trying to explicate characteristics
relationship between obesity and hypertension in children. 16,17
of obese children and to search for relationships between
The signifi cant and independent association between BMI and
Table 2 Number of participants with different cardiovascular risk factors †
† Data are presented as frequency (percentage in parentheses).
‡ Defi ned according to Task Force for High Blood Pressure in
Fig. 1 Distribution of boys with different numbers of cardiovas-
HDL, High Density Lipoprotein; LDL, Low Density Lipoprotein.
Obesity and cardiovascular risk factors 569
Fig. 2 Distribution of girls with different numbers of cardiovas- cular risk factors.
blood pressure (controlling for both child age and height) sup-
ports the hypothesis that early-onset obesity is accompanied by many health risks including hypertension. 18
We found a signifi cant association between BMI and trig-
lyceride levels in overweight or obese children. This was not
true for the association of BMI with total cholesterol and LDL. Li et al. have also found that degree of obesity has no strong correlation with total cholesterol and LDL. 19
Only 2.8% of the children showed low HDL levels and
there was no signifi cant relationship between HDL and anthro-pometric variables in this study, which supports the hypothesis that reduced HDL level may require years of history of obesity
to develop and the degree of obesity would affect HDL levels later in life. 19,20 However, there was a signifi cant relationship between BMI and Apo-lipoprotein B levels in our sample.
These fi ndings support the idea that measurement of the Apo-
lipoprotein B levels is a useful initial approach to cardiovascu-lar risk assessment in obese children. 21 In contrast, we found
no association between BMI and Apo-lipoprotein A levels
which is similar to the fi ndings of other studies on obese chil-
dren. 22 According to some authors, reduced Apo-lipoprotein A
and increased Apo-lipoprotein B levels have a strong correla-
tion with the development and progression of Atherosclerosis,
more so than their equivalent lipoproteins HDL and LDL and
in children these changes are associated with the presence of
CVD in their parents. 23,24 Given the more fl uctuating and unre-
liable nature of triglyceride levels, Apo-lipoprotein B could be
the best choice for assessment of dyslipidemia and cardiovas-cular risk in obese children.
, blood pressure; HDL, High Density Lipoprotein; LDL, Lo
It has been suggested that both fat mass and fat distribution
are important factors in assessing cardiovascular risk even
However, the lack of correlation between
WHR and dyslipidemia of obese children in our study could
be interpreted as this index may be less appropriate for evalu-
ation of cardiovascular risk in children and adolescents than
in adults. We also found no association between hip circum-
ference and dyslipidemia in this study. This is similar to the
results of the Bogalusa Heart Study, which emphasizes that
the hip circumference provides little information on cardio-
ers and health-care professionals to prevent progression of
association between waist circumference and triglycerides,
In summary, we detected a high prevalence of cardiovascu-
Apo-lipoprotein B and blood pressure in this study is in agree-
lar risk factors in overweight and obese children and positive
ment with the results of other studies which suggested that
correlation of these factors with severity of obesity. Future
waist circumference may be better measures of fat distribu-
studies evaluating the possible role of Apo-lipoprotein B in
the pathogenesis and prognosis estimation of obesity are rec-
A combination of major cardiovascular risk factors (includ-
ommended. Hypertension and dyslipidemia in overweight and
ing hypercholesterolemia, hypertriglyceridemia, and hyper-
obese children indicate a serious health risk and emphasize the
tension) as well as insulin resistance are now known as
importance of prevention and control of obesity from early
‘metabolic syndrome’. 26 Studies on prevalence and character-
childhood to improve present and future health status.
istics of this syndrome in children and adolescents also have shown similar results to this study. It has been indicated that the prevalence of ‘metabolic syndrome’ increases signifi cantly
in relation with bodyweight and severity of obesity. 27,28
The main limitation of our study was the poor response
The authors are thankful to Mr. Peyman Shooshtarizadeh in the
rate, as from 1644 invited students only 563 (34%) particip-
laboratory of Endocrine and Metabolism Research Center.
ated in the study. The primary reason for nonparticipation
They also appreciate the support from the Ministry of Education,
could be the necessity of blood sampling in our study, which
Bureau of Tehran, and the pupils of the primary schools in the
decreases the compliance of children. As just about one-third
sixth district of Tehran for their collaboration.
of invited children attended the clinic, we should be cautious to generalize obvious characteristics of these children to the Iranian obese children, however, the paraclinical nature of cardiovascular risk factors assessed in this study decreases
the impact of potential selection bias on our fi ndings.
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