Author's response to reviews
Title: Waist circumference and risk of elevated blood pressure in children: a
cross-sectional study
Authors:
Cheuk-Sing Choy ([email protected])
Wan-Yu Chan ([email protected])
Ta-Liang Chen ([email protected])
Chun-Chuan Shih ([email protected])
Li-Chu Wu ([email protected])
Chien-Chang Liao ([email protected])
Version: 3 Date: 11 July 2011
Author's response to reviews: see over
Associate Editor
Paul Roderick
Deputy Section Editor
Martin O'Flaherty
The BMC Public Health Editorial Office
July 11, 2011
Re: Manuscript 1180867103509815 Revision 1
Title: Waist Circumference and Risk of Elevated Blood Pressure in Children: A
Cross-Sectional Study
Dear Drs. Roderick and O'Flaherty:
Thank you very much for your letter of May 24 informing us to revise the manuscript.
We followed reviewers’ comments to revise the manuscript throughout the manuscript.
This revision has responded point-by-point to the comments.
This is an original article with no prior publication and no submission with any
overlapping information. This article is not under consideration for publication in any
language elsewhere. It will not be submitted to other journal while under review by
the journal ‘BMC Public Health’. No any type of conflict of interest is involved in
this study. The sponsor also has no involvement in our publication. All authors have
read and agreed to this version of manuscript and takes full responsibility for the
manuscript.
Thank you very much for your consideration of this revised paper for publication in
the Journal. We appreciate very much of those thoughtful and helpful comments.
Chien-Chang Liao, PhD, MPH
Medical Investigator
Department of Anesthesiology
Taipei Medical University Hospital
252 Wu-Hsing Street
Taipei 110, Taiwan
Tel: 886-4-2233-9216
Fax: 886-4-2234-5372
E-mail: [email protected]
To reviewer Fall:
1.
Q: The Results section still repeats a lot of numbers already in the tables. For
example, the entire first paragraph of Results could be replaced with the
following sentence: “All anthropometric measurements, including height,
weight, BMI, neck circumference and hip circumference, and all measures of
blood pressure, including SBP, DBP and elevated BP, increased with
increasing waist circumference (Table 1).” If there is anything to be added it
would be a sentence saying that SBP, DBP and the prevalence of elevated BP
rose by X (regression coefficients and 95% CI) per cm increase in WC.
Reply: We changed the descriptions in the first paragraph in the “Results” section
according to your suggestions. Please see page 11.
2.
Q: In paragraph 2 of Results: the first sentence states that boys with elevated BP
had higher WC than girls with normal BP. Surely this isn’t the point. It
would be better to say: “Within each sex, children with high BP had higher
WC than those with normal BP.”
Reply: Yes, the sentence was changed accordingly. Thanks the suggestions. Please
see page 11.
3.
Q: When describing Table 2, it should also be noted that height is also positively
correlated with BP.
Reply: We added the sentence “Height is also positively correlated with systolic and
diastolic blood pressure in boys and girls.” into the second paragraph of
“Results” section, please see page 11.
4.
Q: In the third paragraph of Results, again there is extensive repetition of
figures given already in the Tables. In this unnecessary and long list of ORs,
the important point, that BP is as strongly related to hip circumference as to
waist circumference, does not come out clearly, and should be pointed out.
Reply: We remove the redundant numbers in the third paragraph. According to your
suggestions, we noted that blood pressure was strongly related to hip
circumference as to waist circumference. Thanks the comments.
5.
Q: The authors have not clearly brought out the fact that both WC and BP are related
to stature (skeletal size, height) and overall body weight and fatness (BMI).
Presumably the relationship of neck and hip to BP reflect these relationships. BP
is higher in tall people, presumably as a physiological effect to ensure perfusion of
a taller body. As far as I know it is not known whether the higher BP associated
with being taller is as ‘harmful’ as a risk factor for later disease as the higher BP
associated with being fatter. Anyway, the main purpose of the adjustments in
Tables 3 and 4 is to establish whether the association between WC and BP is still
present after adjusting for these measures of body size. The footnotes of these
tables state that the analyses are adjusted for sex, and yet only one sex is presented
per table.
Instead of the current presentation, I would suggest that Tables 3 and 4 are merged
into one table (sexes combined, with sex retained as an adjustor in all models) and
that the number of outcomes is reduced (either elevated SBP and elevated DBP or
elevated BP, not all 3) and that three distinct models are presented across the page
(should be possible in landscape format): 1) adjusted only for sex, age and
operator; 2) adjusted for sex, age and operator + height; 3) adjusted for sex, age,
operator, height + BMI. We would then see the serial reductions in ORs as one
serially adjusts out the effects of skeletal size and overall body weight or fat,
leaving still substantial effects of WC and HC. This would also make a logical
progression of ideas in the Discussion more attainable.
Reply: We performed new data analysis according to your suggestions. We merged
Table 3 and Table 4 into one table and combined sexes in the dada analysis.
Please see Table 3. The “Results” section was also revised. The corresponding
statements and explanation were added in the “Discussion” section.
6.
Q: The authors have not really dealt with neck circumference, except to say that
it has been included in many other papers about blood pressure! That may be
true, but still some discussion, even speculation, about the meaning of this
association is required. What is neck circumference telling us? Why is it
related to BP? I do not think it helps to add it as an adjustor in Tables 3 and
4 – which would be much easier to interpret if confined to adjustments for
height and BMI. If neck circumference needs to come into the paper, its
association with WC and BP could be mentioned in couple of sentences in
Results.
Reply: According to your comments, we remove neck circumference in Table 3.
Statements regarding neck circumference in the “Discussion” and “Methods”
section were also deleted.
7.
Q: The authors recommend measurement of waist circumference as a screening
tool in children. It could be argued that rather than screening by WC, why
not just measure BP in the first place? The answer is that BP requires greater
operator skill, and is liable to be falsely elevated unless measured with care
and in stress-free situations. Also, high WC is associated with other
cardio-metabolic risk factors, like lipids and insulin resistance. I agree,
therefore that the data, taken alongside what is known about the relationship
of WC to metabolic risk, that screening with WC is a reasonable
recommendation – the authors could argue the case for this more cogently.
Reply: We added the statements “WC is much easier to measure than blood pressure in
relation to training and access to equipment, especially in low income settings. To
measure blood pressure requires greater operator skill, and is liable to be
falsely elevated unless measured with care and in stress-free situations.
Because WC is significantly correlated with blood pressure, we suggested that
the measurement of WC as a screening tool for elevated blood pressure in
children. However, our study presented the moderate sensitivity and
specificity suggesting that using WC to screening elevated blood pressure in
children should be carefully. Some children with elevated blood pressure may
not have large WC, and vice versa.” in the “Discussion” section according to
your comments.
We appreciate your useful comments and suggestions. Thank you very much.
To associate editor:
Abstract
Q: Background
Insert ?This cross-sectional study..?
Methods
Mention Grade 1=age 6-7
Results
All 2334 children were examined (i.e response rate was 100% in the 6 schools).
Conclusion
Is the argument that WC is much easier to measure than BP in relation to
training and access to equipment, especially in low income settings? This needs to
be covered in the discussion.
Reply: We modified the abstract according to your suggestions. Some new statements
were added in the “Discussion” section. “WC is much easier to measure than
blood pressure in relation to training and access to equipment, especially in low
income settings. To measure blood pressure requires greater operator skill, and
is liable to be falsely elevated unless measured with care and in stress-free
situations. Because WC is significantly correlated with blood pressure, we
suggested that the measurement of WC as a screening tool for elevated blood
pressure in children.” Thank you the comments.
Background
Q: Para 1 last sentence
Clarify childhood obesity is associated with high risks of adult hypertension?
etc.
What is the prognostic value of pediatric hypertension?
Reply: The following description was added in the first paragraph of the “Results”
section. “In addition, childhood obesity is associated with high risk of
adulthood hypertension. Children with elevated blood pressures are at
increased risk of hypertension and the metabolic syndrome later in life.”
Methods
Q: You can drop the ?purposive sampling?.
The critical issue over the sampling is the school selection. How typical (size,
location, socio-economic mix of children, public vs private) of the primary
schools in Taipei County were the 12 who have examinations? What % are
they of all primary schools in Taipei County? Also briefly state how
representative is Taipei County of Taiwan.
This will address the need for the sentence starting ?Nevertheless?.? which
can be dropped.) You can say briefly that the age sex distribution of children
in the 6 schools was similar to all 12.
P8 Which instruments were calibrated?
Given you say WC is simple to measure are there any data on intra-operator
or inter operator reliability?
P10
No results are given for the analysis on hip circumference, waist hip ratio or
BMI mentioned in sentence beginning ?For further analysis..?
There is nothing in the methods to describe the process to derive sens and
spec. The PPV and NPV can also be given, based on the prevalence in this
population.
Reply: The inappropriate term “purposive sampling” was deleted according to your
suggestions.
In Taiwan, Taipei County is at the moderate level of socioeconomic status
including education, urbanization, and family income. The population in
Taipei County is representative of the population in Taiwan. In Taipei county,
there were 12 of 211 (5.7%) public elementary schools were involved in this
study.
We added the description “The distribution of age and sex for children in the 6
studied schools was similar to all 12 public schools.” in page 6. In addition, we
moved the sentence “There was no significant difference in age, sex between
children included (n = 2447) and those not included (n = 2695).” from page 6
to page 7. Thanks the helpful comments.
The method of describing the calculation of sensitivity, specificity, positive
predictive value and negative predictive value was added in the “Methods”
section. Please see page 10.
Results
Q: The latter sentences of Para 1 can be significantly shortened.
Reply: The First paragraph was shortened according to your suggestions.
Q: Table 1 BP %s?given the definition used of being above 95% centile for age
gender and height how can each quartile have prevalence over 5%?
Shouldn?t the overall prevalence by 5%?? Title should be 6-7 yr olds
Reply: Elevated blood pressure was defined in students found to have either mean
systolic or diastolic blood pressure greater than or equal to the gender, age, and
height-percentile-specific 95th percentile blood pressure value. The followings
were criteria from National High Blood Pressure Education Program Working
Group on Hypertension Control in Children and Adolescents.
The criteria are based on American pediatric population. Yet, there are no
hypertension criteria for pediatrics based on Chinese population. Therefore,
the prevalence of elevated blood pressure is over 5% in every quartile.
We revised the title of Table 1, thanks the comments.
Discussion
Q: Para 1 Children are 6-7 year olds.
Para 2 Missing sentence that girls maybe more prone to any hypertension than
boys which would lead into the last sentence.
Need to develop the argument raised in abstract?s conclusion.
An argument against using waist height ratio is that its more complex to measure.
(need WC and height).
Should one be measuring BP too alongside WC as this will be more accurate at
predicting metabolic syndrome in children?
What would one do with the WC information? There are interventions targeted
at the whole school population (physical activity at school, school meals etc),
what would one do additionally based on a high WC?
Need to mention generalisibility to all Taiwanese children.
Reply: The sentence in the first paragraph was modified to “This study meticulously
investigated the relationship between WC and elevated blood pressure among
children aged 6-7 years after adjusted for age, sex, operator, height, and body
mass index.” by your suggestions.
You suggest the sentence “girls maybe more prone to any hypertension than boys”.
However, the reviewer requests we combine the sex stratification into one table.
Therefore, we have difficulty to add the sentence which you suggest.
The argument “This study showed that elevated blood pressure in children was
associated with WC which is much easier to measure than blood pressure in
relation to training and access to equipment, especially in low income settings.”
was added in the conclusion.
Interventions were need among children with large WC for lowering blood
pressure.
The sentence “our study could be generalized to the population in the same age
in Taiwan” was included in page 16.
Limitation
Q: add cross sectional study so one cannot infer causaation.
Reply: We added the statements “Furthermore, our study is a cross-sectional study
that could not infer causation.” in the study limitation.
We appreciate your useful comments and suggestions. Thank you very much.