Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Correspondence
  • Published:

Pediatrics

Response to letter from Okutucu and Bursa

International Journal of Obesity volume 43, pages 2344–2345 (2019)Cite this article

Subjects

We would like to thank Dr Okutucu and Bursa [1] for their comments and questions regarding the chronotropic response ratio and statistical perspectives described in the study from Franssen et al. [2].

Furthermore, Dr Okutucu and Bursa commented on the applied statistical methods. They mention that in the multivariate linear regression analysis there is no assumption about normality on the independent variables. We agree with Dr Okutucu and Bursa that errors distribution and shape regression curve can be changed by only transforming the dependent variable. However, the main reason for the skewed data in this regression analysis was due to outliers. In this way, the reason of these conditioning transformations was not to make the independent variables normally distributed, but to eliminate the influence of extreme outliers and in turn to reduce the degree of skewness. One diagnostic measure that can be used to identify possibly influential outliers is Cook’s distance (Cook’s D). It is stated that a data point with Cook’s D > 1 can be treated as an outlier. In our analysis Cook’s D is 2.39 when the outliers are included and 0.28 when the outliers are left out of consideration. Therefore, these outliers cannot be ignored in our multiple regression analysis since these values have a substantial influence on the regression model. Sensitive analysis including, scatter plots, histograms and QQ-plots of regression models, which consisted of variables with outlies, were made. Then, independent variables with outliers were log-transformed and scatter plots, histograms and QQ-plots were made again to verify whether the models became a better predictor of the dependent variable. Indeed in all models became more accurate after log-transformation of the independent variables.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Fig. 1

References

  1. Okutucu S, Bursa N. xxx. Int J Obes. 2019.

  2. Franssen WMA, Beyens M, Hatawe TA, Frederix I, Verboven K, Dendale P, et al. Cardiac function in adolescents with obesity: cardiometabolic risk factors and impact on physical fitness. Int J Obes. 2018. https://doi.org/10.1038/s41366-018-0292-x.

  3. Lauer MS, Francis GS, Okin PM, Pashkow FJ, Snader CE, Marwick TH. Impaired chronotropic response to exercise stress testing as a predictor of mortality. JAMA. 1999;281:524–9.

    Article  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. REVAL—Rehabilitation Research Center, Faculty of Rehabilitation, Hasselt University, Diepenbeek, Belgium

    Wouter M. A. Franssen & Dominique Hansen

  2. Interuniversity Institute for Biostatistics and Statistical Bioinformatics, Hasselt University, Hasselt, Belgium

    Liesbeth Bruckers

  3. Department of Paediatrics, Jessa Hospital, Hasselt, Belgium

    Guy Massa

  4. Heart Center Hasselt, Jessa Hospital, Hasselt, Belgium

    Dominique Hansen

  5. BIOMED—Biomedical Research Center, Faculty of Medicine and Life Sciences, Hasselt University, Diepenbeek, Belgium

    Dominique Hansen

Authors
  1. Wouter M. A. Franssen
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Liesbeth Bruckers
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Guy Massa
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Dominique Hansen
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Dominique Hansen.

Ethics declarations

Conflict of interest

The authors declare that they have no conflict of interest.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Franssen, W.M.A., Bruckers, L., Massa, G. et al. Response to letter from Okutucu and Bursa. Int J Obes 43, 2344–2345 (2019). https://doi.org/10.1038/s41366-019-0454-5

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41366-019-0454-5

Search

Advanced search

Quick links