Review Reports - Influence of a 30-Day Slow-Paced Breathing Intervention Compared to Social Media Use on Subjective Sleep Quality and Cardiac Vagal Activity

Round 1

Reviewer 1 Report

The study presented by Laborde and coauthors is aimed to investigate the effects of a smartphone-based slow paced breathing intervention (6cpm) performed 15 minutes before sleeping during 30 days, compared to a control condition with participants using social media on their smartphone.

This study is aimed to investigate the influence of a 30 days slow paced breathing intervention (experimental group) in comparison to social media use (control group) on subjective sleep quality via the PSQI and on night and morning CVA, operationalized via high-frequency heart rate variability. In comparison to the control group, subjective sleep quality and CVAnight were increased in the experimental group but not in the control group, while there was only a tendency for CVAmorning to display a pattern similar to CVAnigh.

The paper is well written and interesting. I have only minor concerns:

table 1: please check the acronymi because there are some mistakes (i.e. PSQI), some acronymi are not clarified in the note. In general the table is not so readable, please put on the same row HRV morning measureme, HRV night measure;

results: i strongly recommend the use of subtitles instead of 'regarding the...' to describe the results. the results are not easily understood (η², d, t..). The reader will thank you for better formattation of this paragraph.

I strongly recommend the use of this method also in adolescents to educate them to sleep hygiene and to investigate the use of social media, and most of all I recommend to repeat this experiment analyzing partecipants with a polysomnography to avoid subjective interpretation.

Author Response

Comment 1:The study presented by Laborde and coauthors is aimed to investigate the effects of a smartphone-based slow paced breathing intervention (6cpm) performed 15 minutes before sleeping during 30 days, compared to a control condition with participants using social media on their smartphone.

The paper is well written and interesting. I have only minor concerns:

Answer 1 :We would like to thank the reviewer for these positive comments.

Comment 2 :table 1: please check the acronyms because there are some mistakes (i.e. PSQI), some acronymi are not clarified in the note. In general the table is not so readable, please put on the same row HRV morning measureme, HRV night measure;

Answer 2 :We corrected PQSI to PSQI – Pittsburgh sleep quality index, apologies for this error. We have also checked all acronyms within the note. Finally, we put HRV morning and night measurements on the same row.

Comment 3:results: i strongly recommend the use of subtitles instead of 'regarding the...' to describe the results. the results are not easily understood (η², d, t..). The reader will thank you for better formattation of this paragraph.

Answer 3:Thanks for this advice, we have now used subtitles in the results section, and we have added the clarification of the statistical tests used in the data analysis section.

Comment 4:I strongly recommend the use of this method also in adolescents to educate them to sleep hygiene and to investigate the use of social media, and most of all I recommend to repeat this experiment analyzing partecipants with a polysomnography to avoid subjective interpretation.

Answer 4:We fully agree with this comment, and subsequently we have added this recommendation into our discussion/limitation section.

Reviewer 2 Report

Although this is a very interesting topic of investigation the study's design is problematic.

The control condition in this study is not a true control. There is plenty of work showing that media use at bedtime impedes sleep.

Some examples:

Digital Media and Sleep in Childhood and Adolescence.LeBourgeois MK et al. Pediatrics. (2017)

#Sleepyteens: Social media use in adolescence is associated with poor sleep quality, anxiety, depression and low self-esteem.Woods HC et al. J Adolesc. (2016)

Social Media Use Before Bed and Sleep Disturbance Among Young Adults in the United States: A Nationally Representative Study.Levenson JC et al. Sleep. (2017)

Furthermore, the differences in the Pittsburg seem to related to poorer sleep quality in the "control" group post-test (rather than simply improvement in the intervention). I suspect this is also the case in the overnight CVA but I could not identify the descriptive data on overnight CVA from what was presented. This data needs to be included and/or Table 1 needs better heading and description.

In my opinion this manuscript needs a rewrite with better acknowledgement of the methodological issues regarding the "control" group and more balanced interpretation of the results. Alternatively the study needs to be rerun with a control group that does not undergo procedures that are known to have a negative effect on sleep!!

Author Response

Comment 1 :Although this is a very interesting topic of investigation the study's design is problematic.

The control condition in this study is not a true control. There is plenty of work showing that media use at bedtime impedes sleep.

Some examples:

Digital Media and Sleep in Childhood and Adolescence.LeBourgeois MK et al. Pediatrics. (2017)

#Sleepyteens: Social media use in adolescence is associated with poor sleep quality, anxiety, depression and low self-esteem.Woods HC et al. J Adolesc. (2016)

Social Media Use Before Bed and Sleep Disturbance Among Young Adults in the United States: A Nationally Representative Study.Levenson JC et al. Sleep. (2017)

Answer 1 : We completely agree with the reviewer that future research should utilise an additional control group, for example breathing at a normal frequency (12cpm), similar to Tsai et al. (2015), as we mentioned in our limitations.

Tsai, H. J., Kuo, T. B., Lee, G. S., & Yang, C. C. (2015). Efficacy of paced breathing for insomnia: enhances vagal activity and improves sleep quality. Psychophysiology, 52(3), 388-396. doi:10.1111/psyp.12333

In addition to this, we added the consideration that the use of social media may decrease sleep quality within our limtiations, thank you for the references. However in our sample, the control group did not display a poorer subjective sleep quality (PSQI) nor CVA after the intervention (see our Results section).This could potentially be because our participants already had a habitual use of social media priror to sleeping before participating in our experiment, so this did not influence our results.

Comment 2 : Furthermore, the differences in the Pittsburg seem to related to poorer sleep quality in the "control" group post-test (rather than simply improvement in the intervention).

Answer 2 :We thank the reviewer for this comment however, our results indicate that for the PSQI sleep quality significantly improve in the experimental group, but remain constant in the control group : « Concerning simple main effects for time, there was a significant difference between pre-test and post-test for the experimental group (i.e., PSQI score decrease, indicating higher subjective sleep quality), t(31) = 2.881, p = .007, d = 0.51, but no significant difference was found for the control group, t(31) = 1.717, p = .096, d = 0.30.” (p.2, l.236).

Comment 3: I suspect this is also the case in the overnight CVA but I could not identify the descriptive data on overnight CVA from what was presented.

Answer 3 :Again, here our results also indicated that the only significant difference was found in the experimental group, while no changes were found in the control group: “Concerning simple main effects for time, there was a significant difference between pre-test and post-test for the experimental group (i.e., CVA_nightincrease), t(31) = 3.868, p < .001, d = 0.68, but no significant difference was found for the control group, t(31) = 1.655, p = .108, d = 0.29.”

Comment 4:This data needs to be included and/or Table 1 needs better heading and description.

Answer 4:The data was included in Table 1, but now, with the consideration of the comment also from Reviewer 1, we reorganized it and present the descriptive data in Table 2.

Comment 5:In my opinion this manuscript needs a rewrite with better acknowledgement of the methodological issues regarding the "control" group and more balanced interpretation of the results. Alternatively the study needs to be rerun with a control group that does not undergo procedures that are known to have a negative effect on sleep!!

Answer 5:We now acknowledge that further research should use another control group as social media use. However, given our results show that subjective sleep quality (PSQI) nor CVA decrease between pre-test and post-test in our control group (potentially given our participants had already the habitual use of social media prior to sleeping before participating in the experiment), this did not influence the conclusions we were able to draw regarding our experimental group. We hope that this issue is now clarified, and we would like to thank you again for your critical comments that helped to increase the quality of the manuscript.