This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Amin, R. Search for Related Content PubMed Articles by Amin, R.

Outcomes in Children with Obstructive Sleep Apnea

We appreciate the comments offered by Dr. Ng and colleagues on our article (1). We addressed the question of the degree of adiposity and growth velocity in children with persistent sleep-disordered breathing (SDB) whose polysomnographic results at 1 year differed from healthy controls. The study design allowed taking into account the normal variation in the apnea–hypopnea index (AHI) over time in children who are otherwise asymptomatic. Therefore, the study described growth velocity characteristics in a distinct group of children with SDB 1 year after TandA. Although such a design led to using a different AHI cutoff at the beginning and the end of the study, it provided a more rigorous approach to the understanding of the role of growth velocity in SDB. Ng and colleagues' comment regarding the transformation of body mass index (BMI) to BMI z score is valid. We generated models using both variables. In the absence of any significant differences between models using a raw BMI and BMI z score, we reported those with raw BMI.

Omnibus tests of group differences assessed at multiple time-points can help to protect a studywise level but often test hypotheses in which neither the researchers nor the readers have an interest. In our study, the 12-month follow-up was of primary interest, whereas earlier time periods were examined in an exploratory manner so as to possibly elucidate mechanisms producing the longer-lasting effects. A simultaneous test of all time-points increases the chance of making type 2 errors by mixing tests of individual hypotheses that are of varying importance and in which the researchers have varying levels of confidence. In any event, no omnibus test or any other statistical technique will make it possible "to deduce which of the statistical significant results is in fact a false positive," presumably a type 1 error.

Raouf Amin

Children's Hospital Medical Center
Cincinnati, Ohio

FOOTNOTES

Conflict of Interest Statement: The author does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript.

REFERENCES

1. Amin R, Anthony L, Somers V, Fenchel M, McConnell K, Jefferies J, Willging P, Kalra M, Daniels S. Growth velocity predicts recurrence of sleep-disordered breathing 1 year after adenotonsillectomy. Am J Respir Crit Care Med 2008;177:654–659.[Abstract/Free Full Text]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Amin, R. Search for Related Content PubMed Articles by Amin, R.