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Indian Pediatr 2011;48: 765-771 |
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Waist Circumference and Waist for Height
Percentiles in Urban South Indian Children
Aged 3-16 Years |
Rebecca Kuriyan, Tinku Thomas, Deepa P Lokesh, Nishita R Sheth, Anvesha
Mahendra, Renju Joy,
Sumithra S, *Swarnarekha Bhat and Anura V Kurpad
From the Division of Nutrition, St John’s Research
Institute, and *Department of Paediatrics, St John’s Medical College,
St John’s National Academy of Health Sciences, Bangalore 560 034, India.
Correspondence to: Rebecca Kuriyan, Division of
Nutrition, St John’s Research Institute,
St John’s National Academy of Health Sciences, Bangalore 560034, India.
Email: [email protected]
Received: May 07, 2010;
Initial review: June 11, 2010;
Accepted: August 23, 2010.
Published online: 2011 March 15.
PII: S097475591000381-1
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Objectives: To develop age and gender specific waist circumference
references for urban Indian children aged 3 -16 years.
Design: Cross-sectional study.
Setting: Urban preschools and schools of Bangalore.
Participants: 9060 children (5172 boys and 3888
girls) in the age group of 3-16 years.
Methods: Weight, height, and waist circumference
were measured using standard anthropometric methodology. Percentiles for
waist circumference and Waist/height ratio (W/Ht) for each age and gender
were constructed and smoothed using the LMS method.
Results: Mean waist circumference increased with
age for both girls and boys. The upper end of curve in boys continued to
increase, whereas in the girls it tended to plateau at 14 years. The waist
circumference of the Indian children from the present study was higher
than age and sex matched European children. The proportion of children
with W/Ht ratio greater than 0.5 decreased as their age increased.
Conclusions: These curves represent the first
waist and waist height ratio percentiles for Indian children and could be
used as reference values for urban Indian children. We suggest that for a
start, the 75th percentile of waist circumference from this study be used
as an "action point" for Indian children to identify obesity (as a
tautological argument), while retaining the cut-off of 0.5 for the W/Ht
ratio; however this underlines the need to derive biologically rational
cut-offs that would relate to different levels of risk for adult
cardiovascular disease.
Key words: Child, India, Normal values, Obesity, Waist
circumference, Waist-height ratio.
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There are at least 20 million children globally, under the age of 5 years,
who are overweight [1]. Although the health consequences of obesity are
mostly seen during adulthood, it is likely that a tendency to overweight
or obesity could start earlier in childhood and track into adulthood. The
body mass index (BMI) is recommended for identifying overweight and obese
children and youth [2]. The BMI is a measure of excess weight relative to
height rather than excess body fat and may be a less sensitive indicator
of fatness among children [3]. Patterns of fat distribution have shown to
influence cardiovascular disease (CVD) risk and abdominal obesity predicts
CVD risk better than overall obesity [4,5]. There is also increasing
interest in the use of waist circumference as an index of obesity and
obesity-related health risk among children and adolescence, as the waist
circumference has shown strong associations with risk for coronary heart
disease [6]. Thus, obtaining normative information and cut-offs of the
waist circumference in children can be a useful means of identifying
overweight and obese conditions in childhood population studies, and for
identifying those children who could benefit from early intervention.
Waist circumference percentile curves have been
generated for Cuban [7], Italian/Spanish [8,9], British [10], and American
children [11]. In India, data on childhood waist circumference percentiles
is very limited; one study that measured waist circumference derived a
percentile chart for Indian school going children as a product of BMI and
waist-to-height ratio, in a smaller number of children with a restricted
age range [12]. Since urban pediatric obesity levels in India are
increasing [13,14], the aim of the present study was to develop age and
gender specific waist circumference reference data for urban Indian
children 3-16 years of age.
Methods
The PEACH (Pediatric Epidemiology and Child Health)
study was conducted by St. John’s Research Institute, Bangalore in
children recruited from 8 urban middle income preschools and schools in
Bangalore from August 2008 to January 2010. The annual fees of the schools
that were chosen ranged from Rs. 24,000 to 30,000, therefore, the term
"middle income group" was used for these schools. The inclusion criterion
was normal healthy children in the age group of 3 to 16 years. The
exclusion criterion was a significant clinical history. The schools were
selected by using convenience sampling procedure for operational
feasibility. The total sample was 9060 children (5172 boys and 3888
girls). The minimum sample size at each age and sex group was fixed at 100
children, as this is the minimum recommended sample size at each age group
when using the LMS procedure [15] to define percentile curves. However,
for lowest and highest year of age we could not achieve the recruitment of
this number, therefore the percentile values at these specific years
should be read with caution.
Information regarding the study along with the consent
sheet was sent to all parents through the school, along with a
questionnaire to collect data on age, date of birth, sex, and history of
any medical illness of the child. The study was approved by the
institutional ethical review committee and parental informed consent was
obtained.
Anthropometric measurements of weight, height and waist
circumference were measured by utilizing standard methodology [16]. The
body weight was measured to the nearest 0.1 kg using a calibrated
electronic scale (Essae Teraoka Limited, India). The height was measured
to the nearest 0.1 cm. Waist circumference was measured with a
non-stretchable tape by trained nutritionists (exerting the same standard
pressure on the tape) at the midpoint of the lowest rib cage and the iliac
crest, to the nearest 0.1 cm [17], in a standing position during end-tidal
expiration. The within and between measurer coefficient of variation (CV)
was 0.2% and 0.3%, respectively. Waist/Height (W/Ht) ratio was computed as
the ratio of the waist circumference (cm) and the height (cm).
Data are presented as Mean (SD). All analyses were
performed using Microsoft Excel 97. The data consisted of 9060 children
(5172 boys and 3888 girls) aged 3.0-16.9 years and was divided into
distinct age and sex groups. For the presentation of the data in tables,
each age was rounded down to the last completed year.
Smoothed percentiles for waist circumference for each
gender were obtained using LMS method [15]. The LMS method enables
normalized growth centile standards to be developed, and deals generally
with skewness which might be present in the distribution of the waist
circumference measurements. The power L, Mean M and coefficient of
variation S were calculated for each age group. The maximum power required
to obtain normality was calculated for each age group series and the trend
was summarised by a smooth (L) curve. The trends observed for the mean
(M), and coefficient of variation (S), were smoothed using weighted third
order polynomial equations using the Solver routine in Microsoft Excel.
Results
The descriptive statistics for weight, height, BMI,
waist circumference and W/Ht ratio for boys and girls by age are given in
Web Table I. Table I shows the selected waist
circumference percentile values at each age for boys and girls separately.
TABLE I
Smoothed and Weighted Age and Sex-Specific Waist Circumference Percentile Values(cm)
for Indian Children 3-16 Years of Age
Sex |
Age (y) |
Percentiles |
|
|
5th |
10th |
25th |
50th |
75th |
85th |
90th |
95th |
Boys |
3 |
42.9 |
44.0 |
46.0 |
48.4 |
51.1 |
52.7 |
53.9 |
55.7 |
|
4 |
44.1 |
45.3 |
47.4 |
49.9 |
52.8 |
54.5 |
55.7 |
57.6 |
|
5 |
45.2 |
46.5 |
48.7 |
51.5 |
54.6 |
56.4 |
57.8 |
59.8 |
|
6 |
46.3 |
47.6 |
50.1 |
53.1 |
56.5 |
58.6 |
60.0 |
62.4 |
|
7 |
47.4 |
48.8 |
51.5 |
54.8 |
58.6 |
60.9 |
62.5 |
65.2 |
|
8 |
48.5 |
50.0 |
52.9 |
56.6 |
60.8 |
63.4 |
65.2 |
68.2 |
|
9 |
49.6 |
51.3 |
54.4 |
58.4 |
63.1 |
66.0 |
68.1 |
71.5 |
|
10 |
50.8 |
52.6 |
56.0 |
60.4 |
65.6 |
68.8 |
71.1 |
74.9 |
|
11 |
52.2 |
54.1 |
57.8 |
62.5 |
68.1 |
71.7 |
74.2 |
78.5 |
|
12 |
53.7 |
55.7 |
59.6 |
64.7 |
70.7 |
74.6 |
77.4 |
82.0 |
|
13 |
55.4 |
57.6 |
61.7 |
67.0 |
73.4 |
77.5 |
80.4 |
85.4 |
|
14 |
57.4 |
59.6 |
63.9 |
69.4 |
76.1 |
80.3 |
83.4 |
88.5 |
|
15 |
59.7 |
62.0 |
66.3 |
72.0 |
78.7 |
83.0 |
86.1 |
91.3 |
|
16 |
62.4 |
64.7 |
69.0 |
74.7 |
81.3 |
85.5 |
88.6 |
93.6 |
Girls |
3 |
44.3 |
45.3 |
47.1 |
49.3 |
51.8 |
53.3 |
54.4 |
56.1 |
|
4 |
44.6 |
45.7 |
47.7 |
50.2 |
52.9 |
54.6 |
55.8 |
57.7 |
|
5 |
45.3 |
46.5 |
48.7 |
51.4 |
54.5 |
56.4 |
57.8 |
59.9 |
|
6 |
46.3 |
47.6 |
49.9 |
52.9 |
56.4 |
58.6 |
60.1 |
62.6 |
|
7 |
47.5 |
48.9 |
51.5 |
54.8 |
58.7 |
61.1 |
62.8 |
65.6 |
|
8 |
48.9 |
50.4 |
53.2 |
56.8 |
61.1 |
63.8 |
65.8 |
69.0 |
|
9 |
50.5 |
52.1 |
55.1 |
59.0 |
63.7 |
66.7 |
68.9 |
72.4 |
|
10 |
52.2 |
53.9 |
57.1 |
61.3 |
66.4 |
69.6 |
72.0 |
75.9 |
|
11 |
54.0 |
55.8 |
59.2 |
63.7 |
69.1 |
72.5 |
75.0 |
79.3 |
|
12 |
55.8 |
57.7 |
61.3 |
66.0 |
71.6 |
75.2 |
77.9 |
82.3 |
|
13 |
57.7 |
59.7 |
63.4 |
68.2 |
74.0 |
77.7 |
80.4 |
84.9 |
|
14 |
59.7 |
61.7 |
65.4 |
70.2 |
76.1 |
79.7 |
82.5 |
87.0 |
|
15 |
61.7 |
63.7 |
67.3 |
72.1 |
77.7 |
81.3 |
83.9 |
88.2 |
|
16 |
63.7 |
65.6 |
69.1 |
73.6 |
79.0 |
82.3 |
84.7 |
88.6 |
Age: completed age, e.g. 3 y = 3.00-3.99 y |
Figure 1 shows the smoothed computed waist
circumference percentile curves for the 5th, 10th 25th, 50th, 75th, 85th
90th and 95th percentile for boys and girls separately. The upper end of
curve in boys continued to increase, whereas in the girls it tended to
plateau at about 14 years. Table II depicts the W/Ht
percentile values for the boys and girls. The smoothed W/Ht ratio
percentile curves are depicted in Fig. 2. The 90 th
percentile of W/Ht ratio for boys was ≥ the recommended 0.5 ratio, whereas in girls, the
85th percentile value was ≤0.5.
Web Table II depicts the percentage of the
children above the BMI cut off from Cole, et al. [2] for overweight
and obesity, the percentage of children above the 75th and 90th percentile
of waist circumference in British children [10] as well as those above the
0.5 cut-off of W/Ht. On an average 7.8% and 2.5% of the children (both
sexes) were above the Cole, et al. [2] cut off for overweight and
obesity, respectively. However, based on the 75th and 90th waist
percentiles of British children [10], far more of the present Indian
children were over these cut-offs; 48% of the current Indian children had
waist circumferences that were above the 75th percentile and 30% were
above the 90th percentile. In addition, about 21% of the children had a
W/Ht ratio greater than 0.5.
Similar figures existed for BMI based obesity by
sex-wise analyses, but girls had more discordant results with the British
waist circumference cut-off. Using the BMI cut off values of Cole et al.
[2], it was observed that the highest percentage of obese boys (4.2%) and
girls (4.5%) were at age 5. In girls, aged 16 years, the percentage was
6%. In boys aged 14 years, it was observed that 43% had waist circum-ferences
that were above the 75th percentile of British children, while 30% were
above the 90th percentile. In girls aged 14 years, 75% had waist
circumferences that were above the 75th percentile of the British
children, while 54% were above the 90 th
percentile. The highest percentage of children with W/Ht ratio greater
than 0.5 was seen at 4 years in boys (43%) and at 3 years (71%) in girls.
Discussion
Waist circumference percentile curves have been
developed for children from different countries [7-11], and form a useful
alternative to the measurement of BMI in terms of defining adiposity. In
the present study, we have developed smoothed waist percentile curves for
middle class South Indian children of both sexes, aged 3-16 years. These
curves, which were developed on the largest data set available on waist
circumference in Indian children, represent the first attempt to further
our knowledge to develop smoothed waist circumference percentile curves
and to suggest cut offs for defining abdominal obesity in this population.
The waist circumference of the Indian children from the present study is
higher when compared to age and gender matched British children [10],
using similar techniques of measurement. For example, the 75th percentile
values of waist circumference for 16 years was about 5.6% higher in boys
and 12% higher in girls of the present study (compared to the British
children), and this trend existed at all age groups, albeit with smaller
differences. This suggests that urban middle class children in India
already demonstrate leanings towards the adult South Asian phenotype that
has features that are collectively termed "metabolically obese". These
features have been demonstrated in Asian Indians, where a high percentage
of body fat has been found compared to BMI matched white Caucasians and
blacks [18,19].
There are some considerations that are relevant when
addressing the obviously higher waist circumference percentile values in
our Indian children; first, it is possible that since the children of the
present study were from urban middle class schools, they were not
economically disadvantaged nor did they have household food insecurity,
and had free access to food even within the school. Therefore, this study
may have measured waist circumference in children who may already have
been tending towards overweight. However, by the BMI standard, the average
prevalence of overweight was about 7.8%, which is not very high when
compared to prevalence rates reported earlier in North Indian schools
[13]. Second, the mean height of the children from the present study was
also lower than the height of the British children. The rate of stunting
is high in Indian children at about 48% in poor children [20],
nevertheless, it must be considered that even in these urban middle class
schools, the children were possibly not reaching their full capacity for
height, even if the children were genetically different. It is known that
stunted children with access to food develop larger waist circumferences
and weight, along with signs of early cardiovascular morbidity [21,22].
Another question is the choice of percentile for the
cut-off value to determine an overweight or obese waist circumference.
From Web Table II, it is clear that while the BMI based
Cole, et al. [2] standards gave prevalence of overweight that were
less than 10% in general, the UK based waist circumference standard (based
on their 75th and 90th percentile) gave values for overweight and obese
that were in excess of 50%. Clearly, there is a need for population based
waist circumference percentiles and specific population based cut-offs. As
a tautology, it may be considered that the 85th percentile may be more
appropriate as a starting cut-off value, but given the foregoing
discussion about the selection of the present sample of children, it might
be prudent to choose the 75th percentile in the present study data set as
well, to represent overweight.
The waist-height ratio, in principle, is a good measure
to represent the waist circumference in relation to another easily
measurable body proportion so that distortions based on the body frame
size in different populations are removed. It is being used increasingly
to assess the risk of diseases related to central adiposity in adults
[23,24] and W/Ht ratio greater than 0.5 has been suggested as a value for
indicating whether the upper body fat accumulation is excessive and poses
a risk to health in adults [25]. Studies in children using W/Ht ratios [8]
have also shown that the ratio is superior in its ability to predict
cardiovascular disease compared with BMI or percentage body fat. In the
present study, it was observed that the percentage of children with W/Ht
ratio greater than 0.5, decreased with increasing age in boys and girls.
The value of the W/Ht ratio was skewed in the younger children (3-6
years), where the prevalence of children with a W/Ht ratio of greater than
0.50 was higher than 50% in these age groups. This could reflect the
difference in the velocities of growth in height and waist circumference
with age, but also suggests that the most rational employment of the W/Ht
ratio may be in older, school going children.
In conclusion, this study provides reference values and
percentile curves for waist circumference and W/Ht ratio of urban Indian
children. However, within a framework that links anthropometry to
adiposity which links to risk and morbidity, it is very important to
identify precise cut off points for waist circumference and W/Ht ratio
that could equate to different levels of risk for cardiovascular disease.
Until large-scale data are available, we suggest that the 75th percentile
of waist circumference from this study be used as an "action point" for
Indian children to identify abdominal obesity.
Acknowledgment: We thank the school principals,
teacher, parents and all the students that participated in the study. We
would like to thank Dr Dhinagaran and Mr Chandrashekarayya S Hiremath for
their help in the artwork and Mr Lazar for help in the data collection.
Contributors: RK conceived and designed the
study, interpreted the data and wrote the manuscript. TT and SS conducted
the statistical analysis. DPK, NRS, AM and RJ collected the data and
helped in drafting the manuscript. SB was involved in reviewing the
results and critically reviewing the manuscript. AVK was involved in the
design of the study, interpretation of the data and revised the manuscript
for important intellectual content. He will act as the guarantor of the
study. The final manuscript was approved by all the authors.
Funding: None.
Competing interests: None stated.
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