PONE-D-24-50483Factors associated with early sexual debut among adolescents and youth in Mozambique: a geospatial analysis of the Mozambique  2021 AIDS surveyPLOS ONE

Dear Dr. Muleia,

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PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: I Don't Know

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: No

Reviewer #2: No

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Some comments/questions below that I thought would be worth raising in case minor revisions would be of value for the author to consider.

1. Given that a time to event approach is being used, some of the explanatory variables that are noted appeared to potentially be related to periods that occurred AFTER the event. For example, education, marriage, alcohol & drugs, living away from home etc. While the discussion section does acknowledge that the survey is cross-sectional rather than longitudinal, does the fact that some of these variables are only relevant outside of the hazard period raise a broader methodological question? The section talking about the link between marriage and early sexual debut for example got me thinking about what the relationship was between the sexual debut prior to 15 years and the fact that the marriage may be many years later and potentially unrelated to the sexual partner involved in the earlier event. Similar considerations are at play for employment - is this potentially many years after the early sexual debut rather than prior to the event? Perhaps this could be noted explicitly and/or made clear if these variables are actually all within the pre-event window?

2. There are a couple of small typos or things to check - e.g. the formular for the exponential and gaussian covariance functions are the same, the phase "likewise Ganguli and Wand" may be better as "Similar to...", the label under figure 4 says "you" instead of "youth".

3. In Ganguli & Wand, there was detail provided in relation to the number of knots used within the geospatial smoothing, however the current manuscript does not discuss this detail. The Discussion section however does mention that the 'geographical locations' are the enumeration level - is that what is being used for the knots, rather than a low-rank approach using only a subset of knots? (please excuse if I have misunderstood something here)

4. In Ganguli & Wand, the contour plot of the geospatial factor focused on the log hazard ratio in order to draw attention to where geography seemed to impact the hazard ratio. Would this be worth considering in Figure 4? It's not quite clear what the contour scale is showing at the moment.

5. The socio-demographic profile notes that early debut is significantly more likely for males than females, but the Kaplan-Meier section immediately following calls out that this difference is not significant. Does that warrant a highlight?

6. Similar to #5, there are several references that appear to be conflicting in terms of whether northern/central/southern regions have higher vs lower hazard - e.g. the prevalence rates in table 1 show the northern with a higher prevalence, similar with the Kaplan-Meier results, however the cox model results in table 3 suggest that the northern region (which is the reference) has a lower hazard rate than the others.

Note: I have answered "no" to the data being available, as it seemed that only the raw survey data would be available and the reviewer question seemed to suggest that 'all data underlying the findings' (e.g. 'datapoints behind means') being made available.

Reviewer #2: Thank you for the opportunity to review “Factors associated with early sexual debut among adolescents and youth in Mozambique: a geospatial analysis of the Mozambique 2021 AIDS survey”. The authors data from a national survey to describe an important issue. In general, this paper is clear and well written. However, the authors seem to struggle between presenting results, and defending their modeling strategy in great detail. As a public health epidemiologist, I would encourage the authors to focus on the former, and consider a second methods paper to consider the latter. Below are a few suggestions that I feel may help to improve the paper.

Abstract: Currently, the abstract talks in broad generalities, with no specifics. I appreciate why the authors might have done this, but I ask they consider at least a few numbers. What is the N of their study? What is the overall % of early sexual debut (or, if they wish, the regional % given the assertion of differences)? You don’t need to provide too many details (I think it’s fine, for example, to list correlates, without presenting your measures of effect), but at least tell us the size of your study, and your overall estimate(s).

Abstract: I recommend that you specify the ages of your adolescent and youth data set (i.e., ages 15-24)

Methods, line 79: Why did you consider a subset and not the full data set? How did you select your subset? Your subset represents what percentage of the whole data set?

Methods: can you make your R code and data set available as supplemental material? Your analysis is an interesting one, and I’m sure some readers may be intrigued to review your work and learn more.

Results: Minor point, but “had sex” should probably be “reported having had sex” or similar. Did you do anything to consider reporting bias? Younger participants may have been less confident or comfortable discussing sex and sexual debut, and may have been less likely to report sexual activity.

Results, line 220: Please be cautious with statements like “the prevalence is marginally higher” as the prevalence is statistically equivalent. I do not recommend making claims of modest or marginal difference, where this is really not the case (to me, a “modest” difference is a small, but statistically significant difference, where what you’re showing is very clearly equivalent prevalence across both groups). Kindly go through your paper and consider removing any other claims of this nature.

Results, line 222: How do you define “high” vs “low” socio-economic status? I could not find this specified in your methods.

Results line 242-3: I thought your outcome was early sexual debut, not just sexual debut? This sentence wasn’t very clear to me. Your methods make clear that your outcome is not sexual debut, yes/no, but rather age at sexual debut.

Results, model selection. This section is very technical, and I’m not sure it brings much to the discussion of sexual debut. What is the importance/rational for comparing “circular, exponential, Gaussian, multiquadratic inverse, Mat´ern, and spherical covariance functions” and what is this telling us about age of sexual debut in Mozambique? Some of this section may be best suited to the discussion, or to a more detailed methods paper to describe why you selected the model you did. I don’t think this belongs here in the results, however – or perhaps in a less technical, distilled sentence or two. (Same with Table 2)

Results, “Covariate effects”: Are you modeling “sexual debut” as a bivariate, yes/no, outcome (e.g., lines 281, 283, 284, etc)? That’s how this section reads. However, your methods section makes it sound like you are modeling time to sexual debut? Or early sexual debut (i.e., sex before age 15), yes/no? Please clarify.

Table 3: similar to above, I recommend clearly stating your outcome in the table header. Time to sexual debut? Report of sex before the age of 15 (i.e., yes/no)?

Results, spatial trend: I would encourage the authors to avoid technical jargon in the results. It’s good to explain what you did in the methods, but in the results section, I recommend stating what you found (only). I can refer back to the methods if I wish for more details. (i.e., edit to remove “visualization of the radial basis spline” and “overall geoadditive model” etc)

Discussion: The authors seem torn between presenting their results, and discussing the merits of their modeling approaches. The whole first paragraph of your results re-states your modeling strategy! If I’m hear to learn about early sexual debut in Mozambique, I likely have little interest (or background to understand) why you adopted one strategy over another. I think you may have two papers, here, a methods paper (where you can go much deeper) and a results paper (where you really should limit much of your discussion of methods). Start your discussion with a high level summary of what you found (ie., remove the first paragraph of the discussion –I am guessing most with an interest in the topic would want to start with your second paragraph).

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Reviewer #1: No

Reviewer #2: Yes: Matt Price

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PONE-D-24-50483R1Factors associated with early sexual debut among adolescents and youth in Mozambique: a geo-additive survival analysis of the Mozambique 2021 AIDS indicator surveyPLOS ONE

Dear Dr. Muleia,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

The previous editor was not available, so that I have taken their role in the revision. Among the two previous reviewers only reviewer 1 was available, and proposes to accept the manuscript. Reviewer 2's suggestions have been, according to the new editor, taken up.My only concern is with the reaction to the first issue raised by reviewer 1.403-404Moreover, most of the variables analyzed, such as education, marital status, and employment, may pertain to periods following the event of interest (sexual debut). ​

I think this shoud be clearer and more comprehensive.

Clearer: The variables measure current conditions at the time of the survey so that they reflect events happening after the sexual debut.

More comprehensive: You have mentioned some of the least problematic variables on that respect. I think there are three variables that are more problematic:

- Sex of household head: I would drop it from the analysis. I do not know what is the rationalle, but note how this would be different in married/divorced from unmarried adolescents living with their parents. It will confound different effects. You are not providing any rationale. I would remove it overall from the study.

- Recent consumption of alcohol / illicit drugs. In this case there could be reversed causality.

- Marital status: You have mentioned this as a factor for early sexual debut and, in this case, you expect a causal effect from early marriage to early sexual debut. It is true that marriage behaviour could also adapt after early sexual debut leading to reverse causality.As commented: make clearer, and more comprehensive. Include the words reverse causality where appropriate.

Please submit your revised manuscript by Jul 12 2025 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

José Antonio Ortega, Ph.D.

Academic Editor

PLOS ONE

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Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: I observed a small number of typographical errors that would be worth fixing if possible - e.g. the figure of 18.9% early debut sex is also quoted as 18.8% elsewhere in the paper. There is also a typo "individual male individual" and the word "analyzes". Small observations.

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Reviewer #1: No

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Factors associated with early sexual debut among adolescents and youth in Mozambique: a geo-additive survival analysis of the Mozambique 2021 AIDS indicator survey

PONE-D-24-50483R2

Dear Dr. Muleia,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

José Antonio Ortega, Ph.D.

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

In the opinion of this editor, the authors have satisfactorily introduced the changes suggested by one reviewer and the editor on the previous draft.

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