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Additional Editor Comments (if provided):

Dear Authors,

Thank you for submitting your manuscript to Plos One.

I would like to state that this is a well-conducted economic analysis and a well-written article which I enjoyed reading.

I have now reached a decision which is Major Revision.

In addition to the comments from the reviewers, please see below my comments:

1. Could the authors please justify not including non-Dutch speakers in the study?

2. Similarly to the comment from another reviewer, could the authors please clarify why they considered productivity losses in a population group of elderly and potentially retired participants? Could the authors please elaborate if excluding productivity losses would have an impact on cost-effectiveness results?

Thank you.

Good luck with revising the article.

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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?

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: Yes

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

The PLOS Data policy

Reviewer #1: No

Reviewer #2: Yes

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

Reviewer #1: Yes

Reviewer #2: Yes

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Reviewer #1: General comments:

This manuscript describes a well-conducted economic evaluation of the In Balance intervention compared with physical activity recommendations in non-frail and pre-frail older adults with a high fall risk. The manuscript reads well and the provided information is clear. Findings support the conclusion. Some clarifications would be helpful on methodological choices that were made.

Specific comments:

• Introduction (p. 4, line 65): You say that In Balance is a widely implemented intervention. Is it widely implemented in the Netherlands or Europe or the world? In line 74 you say that it is important to evaluate the cost-effectiveness to inform policy makers to optimally allocate resources or to arrange reimbursement. Given that it is already implemented, how is the intervention financed now? Are there concerns regarding implementation (e.g. are the right people reached)? In other words, why is it important to do the cost-effectiveness evaluation now that the intervention is already implemented?

• Introduction (p. 5, line 85): why was physical activity recommendations (line 85) or exercise recommendations (line 87) chosen as the control condition? Can this be considered usual care or an active (or passive?) control condition?

• Methods – Participants (p. 6, line 109): Why were frail participants excluded?

• Methods – Intervention and control group (p. 7, line 131): Could you please describe briefly what these physical activity recommendations were?

• Methods - Costs (p. 7/8): Were costs of the intervention itself measured and if so, how?

• Methods – Costs (p. 8, line 139): Given the inclusion criterion of being aged 65 years and over, and the retirement age being 67, I wonder how relevant it was to include costs of lost productivity (IPCQ). With the average age being 75 years, how many participants were in paid work? Unpaid work is probably more important in this age-range. The types of activities people do and the hours per week varies a lot. How reliable/realistic is it to use one shadow price for all these different activities?

• Methods – Sample size (p. 0): An expected effect size of 50% seems overly optimistic given effects founds in previous falls prevention trials. What was this expectation based on?

• Methods - Imputation (p. 10): What was the proportion and pattern of missing values? Later I noted that this information was provided in the Results on page 12. Perhaps consider moving this information to the methods, so that the reader understand methodological choices that were made early on.

• Results – Table 1: How were the descriptive variables measured, particularly physical activity?

• Results – Adverse events (p. 19): Please describe how adverse events were measured in the methods.

• Discussion (p. 20, line 349): You describe here that your results align with similar recent international studies, but how does it compare with other Dutch studies, for example:

o Hendriks et al. Cost-effectiveness of a multidisciplinary fall prevention program in community-dwelling elderly people: a randomized controlled trial (ISRCTN 64716113). Int J Technol Assess Health Care. 2008 Spring;24(2):193-202. doi: 10.1017/S0266462308080276. PMID: 18400123.

o Peeters et al. Multifactorial evaluation and treatment of persons with a high risk of recurrent falling was not cost-effective. Osteoporos Int. 2011 Jul;22(7):2187-96. doi: 10.1007/s00198-010-1438-4.

As the health care system and access to services has a great influence on costs, comparison of results with studies within the same/similar health care system may be more relevant than comparison with studies in different countries/health care systems.

• Discussion (p. 21, line 378): If I interpret this sentence correctly, then you describe here that the sample was representative of the population that typically receives the In Balance intervention. The level of education in this sample was quite high. Does this reflect the general population that receives In Balance? Might this suggest that extra efforts are needed to reach groups with lower levels of education?

• Discussion (p. 21, lines 367-390): “Moreover, although we used an optimal number of …. of the In Balance intervention.” Apologies but I do not understand this sentence or what is meant here. Which groups are you talking about here? Weren’t there 131 and 133 participants in the intervention and control groups, respectively? Why 12 per group? Can you please rephrase to clarify the point you are making here?

Reviewer #2: Dear Editor,

I write to submit my comments on the manuscript titled “The cost-effectiveness of the Dutch In Balance fall prevention intervention compared to exercise recommendations among community-dwelling older adults with an increased risk of falls: a randomized controlled trials”

The study, via a randomized controlled trial, evaluated the cost-effectiveness of the In Balance fall prevention intervention for community-dwelling older adults with an increased risk of falls compared to general physical activity recommendations (control) from a societal perspective.

Here are my comments

The outcome measures are the number of falls, fall-related injuries, and Quality-Adjusted Life Years (QALYs) based on the EuroQol Five-level questionnaire (EQ-5D-5L) and the Adult Social Care Outcomes Toolkit (ASCOT).

1) Clarification: The authors indicated that the control group received written general recommendations on physical activity via a flyer, in accordance with the World Health Organization's physical activity guidelines and the intervention group received the “In Balance”. Is it the case that the intervention group actually received the physical activity in accordance with the World Health Organization's physical activity guidelines plus the “In Balance,” OR they only received just the Inbalance? That is control=A and Intervention=A+B. Kindly provide clarity on that. This is also important because the intervention group may be involved in physical activities similar to those described in the WHO physical activity guidelines.

2) In line 133, the authors indicated outcome measure and mentioned cost but also said also said in line 159 that the primary outcome measures in this trial were the number of falls and the number of injuries due to a fall

3) Authors indicated that multiple imputation by chained equations were used but authors did not provide any information on the missing mechanism assumption (missing at random, missing completely at random and missing not at random) and justification as to the choice of a selected missing mechanism

4) What was the measurement scale of the outcome measure? Number of falls for instance is a count outcome measure and cost may be continuous. How did the authors analyze the count outcomes? Were they treated as continuous to fit Zellner's seemingly unrelated regression? Or were they treated as counts and fitted Poisson or negative binomial models?. I think more clarity must be provided regarding the measurement scale of the outcome measures, especially when in some cases is cost and in other cases is number of falls etc. The appropriate regression models must be applied in each case.

5) Authors must clarify if they employed a robust standard error estimation in fitting the seemingly unrelated regression. The standard error estimation will affect the confidence intervals of the effect size estimates

6) Authors must present results on complete case analysis as part of the sensitivity analysis to help determine how the results vary compared to pooled effect estimates from the multiple imputation by chained equations

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what does this mean? ). If published, this will include your full peer review and any attached files.

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Reviewer #1: No

Reviewer #2: No

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The cost-effectiveness of the Dutch In Balance fall prevention intervention compared to exercise recommendations among community-dwelling older adults with an increased risk of falls: a randomized controlled trial

PONE-D-25-05745R1

Dear Prof Bosmans,

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.

I would, however, suggest that you amend the phrase 'usual care condition' used in the Introduction to 'usual care' as I believe you are referring to the control group that received 'usual care' rather than the physical condition itself.

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,

Rositsa Koleva-Kolarova

Academic Editor

PLOS One

Additional Editor Comments (optional):

I would, however, suggest that you amend the phrase 'usual care condition' used in the Introduction to 'usual care' as I believe you are referring to the control group that received 'usual care' rather than the physical condition itself.

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

Reviewer #2: All comments have been addressed

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

Reviewer #2: Yes

**********

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

Reviewer #2: Yes

**********

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

The PLOS Data policy

Reviewer #2: Yes

**********

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

Reviewer #2: Yes

**********

Reviewer #2: The authors have adequately responded to all my previous comments and have provided clarity in the manuscripts

**********

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 #2: No

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