PONE-D-20-29752

Childhood food insecurity and incident asthma: a population-based cohort study of children in Ontario, Canada

PLOS ONE

Dear Dr. Clemens,

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PLOS ONE

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2. Thank you for submitting the above manuscript to PLOS ONE. During our internal evaluation of the manuscript, we found some minor occurrences of overlapping text with the following previous publication(s), some of which you are an author, which needs to be addressed:

- https://onlinelibrary.wiley.com/doi/abs/10.1111/dme.14396

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'Outside of this work, KC received a research award, sponsored in part by Astra Zeneca. She has attended Merck sponsored conferences. She has received honoraria for delivering Certified Medical Education Talks from Sutherland Global Services Canada ULC, the Toronto Ontario Knowledge Translation Working Group Inc and the Canadian Medical and Surgical Knowledge Translation Group. There are no other conflicts of interest to disclose.'

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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: Partly

Reviewer #2: Partly

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

Reviewer #1: I Don't Know

Reviewer #2: Yes

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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: Yes

Reviewer #2: Yes

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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: Study is interesting but I have some concerns related to covariates and findings.

1. It is not very clear which covariates were included in the adjusted models. How they were chosen for the final models? Not all covariates are real confounders and models might be “overfitted”. You should consider using some methods for choosing confounders, like causality graphs. For example, when comorbidities were defined and were they included in the final model? They might be consequences of food insecurity and should not be included as confounders. What are clinical confounders and socioeconomic confounders? They should be explained as footnotes in the main tables and also in the text. How covariates were grouped or removed (page 15)?

2. You report that the association between food insecurity and incidence of asthma is non-significant after adjustment for all the confounders. However, in S7 Table you report significant adjusted hazard ratio for severe food insecurity (vs. food secure) and a dose-response effect for 3-category definition of food insecurity. Why this finding is not reported as a main finding? P value for trend should be reported. It seems that the study conclusions are inconsistent with the results.

3. Please, combine T4 and T5 and explain clinical and socioeconomic confounders in the footnote.

4. In Table 1, study characteristics are presented against exposure variable and in S9 Table against outcome variable. They should be presented similar way in both tables.

5. You present results by respondent type but other possible modifying effects should also be investigated, such as effect of sex and maternal asthma. Also interactions should be investigated.

6. In the Discussion page 22, you write that your findings differ from previous studies. Please, rewrite this paragraph after considering the suggestions above.

Reviewer #2: The manuscript addresses an interesting topic, the relationship between food security and the incidence of childhood asthma. Several methodologic considerations and the overall lack of detail dampen my enthusiasm for the analysis as currently presented.

Major points:

I suggest presenting a biologic mechanism that justifies an induction period of 12 months, particularly since the majority of children had moderate food insecurity. Along those lines, I would have like to have the definition of secure, moderate and severe food insecurity.

Rationale for combining moderate and severe food insecurity in terms of asthma risk. The citations used to justify the exposure variable addressed mental health and health care costs, not asthma.

The age range includes children < 3 years old where a diagnosis of asthma is unreliable. This is a major limitation of the manuscript.

Not enough information is given on the data sources. For example – what are the coverage rates? Is it reasonable to think that families of low income status and recent immigrants would be less likely to have completed the CCHS. No information on coverage rates for any data source were provided.

Important risk factors are missing (environmental, psychosocial, housing quality, etc) and these limitations should be highlighted more. History of respiratory infection was mentioned as a covariate but it appears the variable was actually RSV specifically.

There wasn’t enough information in the manuscript describing the covariates. I find it awkward to have to go to a supplemental table to obtain variable definitions. I suggest defining the covariates in the manuscript and the data source. For example: social deprivation is very important but I can’t judge its validity due to lack of information. Many covariates that appear in the table are not mentioned in the text.

I believe there is a typo in the Results ‘26,336 food insecure’ - I think they mean secure. ‘1,414 secure’ = insecure

Table 1: for variables where quintiles are presented, at least present the data range so the reader has an idea of what the levels are.

Table 1: there’s no definition for many variables. For example – dependency, deprivation, instability, obesity.

Table 2. No need to include both yes and no. Same comment as above for income. Added category of moderate food insecure which wasn’t mentioned in the exposure section. Overall, there are too many categories for several of the variables.

Table 3. Present units: like age in years, etc. There is no definition for immigrant status, charlson score.

Table 5. Tables should stand alone. What are the models adjusted for?

The section of prevalent asthma lacks any detail – most of the information is in the supplemental table. This is difficult to evaluate. I suggest including the essential information or, if there is not room, to remove it.

The literature review lacks consistent detail on all studies cited: add age range and location of all studies. Comparing this study, with an age range of <18 to other studies is problematic and the authors should discuss these differences in depth. Editorial suggestion: include age ranges, not just the grade level as this may change between countries. Also there’s no mention of how the exposure variables are similar or different between studies making it hard to decide if these studies are at all comparable.

Given the weaknesses of the study, I believe the conclusions are overstated.

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Reviewer #1: No

Reviewer #2: No

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Childhood food insecurity and incident asthma: a population-based cohort study of children in Ontario, Canada

PONE-D-20-29752R1

Dear Dr. Clemens,

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,

Maria Christine Magnus, MPH

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

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: No

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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: Thank you for your response. I think you addressed all my comments and I have no further comments to add.

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No