Clinical, Sleep, and Chronobiological Characteristics of Children with Smith–Magenis Syndrome Under Treatment for Sleep Disorders

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Manuscript ID: children-3924219

It is well known that the children with SMS typically exhibit intellectual disability, anxiety, sleep disorder and inversion of melatonin circadian rhythm. In the current study, the authors examined the clinical, sleep, and chronobiological profiles of children with SMS under treatment, and assessed the effects of melatonin and β-blockers on sleep quality and melatonin circadian rhythm. The study has been designed and executed nicely. The authors concluded that sleep treatments did not ameliorate sleep difficulties in children with SMS and that exogenous melatonin and beta-blockers provided partial benefits. However, I have outlined below a couple of issues that should be addressed by the authors.

Line #50: What is ‘treatment 48h washout?’

Line #107 versus Line #200:  aged between 5 and 13 years old versus in children aged 6 to 13 years old. Is this an incongruity?

Table 1: The authors did not mention about the status of menarche especially in the subjects aged between 10 and 13 y. Did some of the subjects experienced their first period?

The standard deviations can not be negative. Please look at the subject codes #01, #05, #09, #10, #12-17, #19, and #20.

What does ‘No’ mean in the last column of this Table?

Is there any explanation for the dissimilarities in the treatment given to the subjects? How can this influence the overall findings?

Table 2: The sample size is very small in case of subjects with beta-blockers.

Did the authors find out any statistically significant differences in the amount of social jetlag between the patients with and without beta-blockers?  

Figure 2: What is ‘Short form?’

Figure 3a: Why there are so many outliers for cortisol in the group without beta-blockers?

Figure 3b: Why the salivary melatonin profile is episodic in the patients? Any explanation for this phenomenon!

Conclusion: How does the overall cohort size influence the conclusion drawn based on the findings of this study?

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This study provides valuable preliminary insights into the complex sleep and circadian challenges faced by children with Smith-Magenis syndrome and the effects of melatonin and β-blockers. Its strengths lie in the comprehensive, multi-modal assessment and clinical relevance. Applying liquid chromatography with tandem mass spectrometry (LC-MS/MS) is also a stronger methodical point. However, limitations in sample size, control conditions, and treatment subgroup sizes temper the strength of the conclusions. Before paper can be recommended there are several crucial concerns that need clarification:

The manuscript states that salivary melatonin and cortisol levels were determined using LC-MS/MS. Even though experts in the field noticed the higher melatonin levels in early age (doi: 10.1093/sleep/zsad033), the reported, notably daytime values, appears unrealistically high. While LC-MS/MS is a highly specific and accurate analytical method, concerns remain regarding the reported data quality and its interpretation. The reported daytime salivary melatonin concentrations, particularly those cited in the abstract (“very high daytime salivary melatonin persisted despite treatment 48h washout”) and the exclusion threshold (>1000 pg/mL, with values stated as >100 pg/mL being unrealistic), are exceptionally high and raise questions about their physiological relevance. Typical daytime salivary melatonin ranges are significantly lower (<10-20 pg/mL).

Therefore, I would invite the authors to provide:

1. Intra- and inter-assay coefficients of variation (CVs) for melatonin at low concentrations, lower limit of quantification, and spike-recovery data.

2. Including statistical details of 24-hour melatonin profiles per time fragment (mean, median, standard deviation, interquartile range and evidence supporting their interpretation as biologically significant.

3. Explain the use of personal reference data, including sources and applicability to Smith-Magenis syndrome.

4. Detail protocols for collection, storage, and controls against contamination.

5. The prescribed melatonin doses appear excessively high. Authors are invited to discuss their relevance, as supraphysiological doses have been shown to desensitize melatonin receptors and render them physiologically irrelevant.

6. To differentiate between potential iatrogenic effects of excessive melatonin supplementation and Smith-Magenis syndrome per se, a discussion comparing Smith-Magenis syndrome patients without treatment (washed-out state) versus those with treatment is needed.

7. Discuss the applicability of actigraphy and the specific devices used for minors, as standard actigraphs are not suitable for the small wrists of children.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

None

Reviewer 2 Report

Comments and Suggestions for Authors

I am thankful to the authors for thoroughly addressing my concerns. I recommend this work for publication. However, I have one suggestion:

The single patient with “normal melatonin levels” in the absence of exogenous supplementation is a crucial observation. This finding strongly supports the iatrogenic source of abnormal melatonin profiles in your treated Smith-Magenis Syndrome cohort. Please emphasize this point more forcefully in both the Discussion and Conclusion sections to highlight its significance and implications for understanding the impact of melatonin treatment.