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Recent rapid responses
Rapid responses are electronic letters to the editor. They enable our users to debate issues raised in articles published on bmj.com. Although a selection of rapid responses will be included as edited readers' letters in the weekly print issue of the BMJ, their first appearance online means that they are published articles. If you need the url (web address) of an individual response, perhaps for citation purposes, simply click on the response headline and copy the url from the browser window.
Displaying 1-5 out of 5 published
8 March 2013
Dear Editors:
Minor corrections are required for the description of the sample size calculation in our paper titled “Effectiveness of a home-based early intervention on children’s BMI at age two years: randomised controlled trial.” BMJ 2012;344:e3732. The revised text, which will have no effect on the overall results, should read as follows:
“The sample size calculation was based on the primary outcome, BMI or BMI z-score, which was assumed to have a SD of 1.5, or 1.0 respectively. To have 80% power to detect a difference in mean BMI of 0.38, or mean BMI z-score of 0.25 units between the groups at age 2 at the two sided 5% significance level, we needed a sample size of 252 per group.”
We reported the outcome in terms of BMI z-score in the responses to our paper at http://www.bmj.com/content/344/bmj.e3732?tab=responses
We sincerely apologise for this error.
Would you please also draw this to the attention of Philip Sedgwick, who used our article as an example in his paper “Sample size: how many participants are needed in a trial?” BMJ 2013;346:f1041.
Competing interests: None declared
Health Promotion Service, Sydney Local Health District, Missenden Rd. Camperdown, NSW 2050, Australia
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+27 July 2012
Thank you for your work and your article, it proved to raise a lot of debate and discussion within our unit.
As said in your article, obesity is intrinsically an intergenerational process. In clinical practice, we do see significant number of obese or overweight children and they tend to have parents who are obese or overweight. From the data reported in your article, it appears that the intervention group of children had a slightly lower weight and slightly longer length at 2 years of age, with a lower BMI when the 2 sets of parameters were put together. I wonder if you have any data on mother's, or perhaps even biological father's, weight and height, and thus their BMI in the 2 groups? I am curious that these factors could be potential confounders and they were not addressed in your article.
Competing interests: None declared
Bronglais General Hospital, Angharad Ward, Bronglais General Hospital, Aberystwyth
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+20 July 2012
Author’s response to A/Prof Daymont’s comments:
In addressing A/Prof Daymont’s comments, we would like to provide additional data reporting differences in mean BMI-, weight-and length-for-age z-scores at 24 months using WHO Anthro.(1) As shown in the additional table, the intervention resulted in a significant reduction in BMI-for-age z-score of 0.29 (P=0.005). There were no significant differences in length-for-age z-score or weight-for-age z-score between the groups. The table also shows that the mean z-scores for BMI, weight and length were above 0 for both groups, and both groups had similar standard deviations (SD). Therefore, the intervention group as a whole was not underweight. In fact, using the WHO classification of underweight (weight-for-age z-score <−2) we had only two cases of underweight in our study: 0.4% (1/234) for the control and 0.4% (1/249) for the intervention group. We think it unlikely that an intervention that focuses on promoting healthy infant/child feeding, active play and a reduction in TV time would lead to poor growth. In addition, the reason for not including child sex in the baseline characteristics of our paper (Table 1)(2) was that we randomised the mothers before they gave birth. Despite a somewhat higher proportion of boys in the intervention group (53%, 131/249) than the control group (46%, 108/234), this difference was not statistically significant (P=0.16).
References:
1. WHO Anthro for personal computers, version 3.2.2, 2011: Software for assessing growth and development of the world's children. Geneva: WHO, 2010 (http://www.who.int/childgrowth/software/en/).
2. Wen LM, Baur LA, Simpson JM, Rissel C, Wardle K, Flood V. Effectiveness of home based early intervention on children’s BMI at age 2: randomised controlled trial. BMJ 2012;344:e3732
Authors:
Li Ming Wen, Louise Baur, Judy Simpson, Chris Rissel, Karen Wardle, and Vicki Flood
Competing interests: None declared
South Western Sydney & Sydney Local Health Districts, Missenden RD. Camperdown , NSW 2050, Australia
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+2 July 2012
Childhood obesity is a challenge that affects the whole world. Drugs and doctors do not carry a ready-made solution to the obesity problem in children and the psychological effects their parents experience. This article is excellent not only because of its interventional strategy but also because of educating parents indirectly that breastfeeding is the best for the health of children, the timing of giving solid foods is important, the intake of fruits and water in good quantities and being active are the key to the problems of delaying or preventing the setting in of obesity in children. This take home message authenticated by scientific results will allow many more studies to be carried out and prove an effective way to tackle the problem of childhood obesity that will later precipitate adult obesity.
Prevention is still the best medicine one could aspire to in a world advised to become drug-dependent for every illness that haunts society.
Competing interests: None declared
Faculty of Medicine, Benghazi University, Benghazi, Libya
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+28 June 2012
I was very interested to read about the community-based intervention for obesity prevention described in “Effectiveness of home based early intervention on children’s BMI at age 2: randomised controlled trial.” I am writing to raise two concerns about the reporting of the trial.
The first, and more important, concern is that no information was provided regarding the proportion of children who were underweight as defined by BMI-for-age and weight-for-age in the control and intervention groups. Any intervention that results in a decrease in mean BMI has the potential to increase the proportion of children who are underweight. This information is important for interpretation of this study and would facilitate planning of future studies. Given the number of participants in the trial it is unlikely that there will be a statistically significant increase in the proportion of children who are underweight, just as there was no statistically significant decrease in the proportion of children who were overweight. It would also be useful to know whether, and in what manner, the intervention was modified for children who were gaining weight poorly.
The second concern is the lack of information regarding the sex of the child participants combined with the use of BMI rather than BMI-for-age z-score. Expected BMI at age 2 years of age (using length rather than height as is done in this study) is 15.4 kg/m2 for girls and 15.7 kg/m2 for boys according to the WHO growth standards.(1) Although it is likely that the proportions of males and females were similar between the groups given the randomized nature of the trial, I believe it is important to report the actual proportions.
Sincerely,
Carrie Daymont
1. WHO Multicentre Growth Reference Study Group. WHO Child Growth Standards Length/height-for-age, weight-for-age, weight-for-length, weight-for-height and body mass index-for-age: Methods and development [Internet]. 2006. Available from: http://www.who.int/childgrowth/publications/technical_report_pub/en/inde...
Competing interests: None declared
University of Manitoba, AE302-671 William Ave, Winnipeg MB, R3P 1C6, Canada
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