Dear Dr. Nadrian,

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Mehdi Rezaei

Academic Editor

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?

Reviewer #1: Yes

Reviewer #2: Partly

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

Reviewer #1: Yes

Reviewer #2: No

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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: Yes

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: Dear editor Dr. Mehdi Rezaei Academic Editor in PLOS ONE

Thank you for your invitation to review manuscript entitled “The Effectiveness of the Home Care Support Intervention Program (HoSIP) to Reduce Loneliness among Community-dwelling Older Adults: A two-year follow-up study”

This article offers valuable and timely insights into the long-term effects of a community-based peer support intervention (HoSIP) aimed at reducing loneliness and improving the quality of life among older adults. One of the main strengths of this study is its mixed-methods design, which combines quantitative measures with in-depth qualitative interviews to provide a comprehensive understanding of both outcomes and lived experiences.

The study is particularly significant because it follows participants for two years after the intervention, capturing sustained impacts on social connectedness, self-confidence, and emotional well-being. This long-term perspective is often lacking in similar research. Moreover, the article highlights the adaptability and sustainability of the intervention, showing how older adults continued to expand and self-manage the program beyond the initial implementation.

Introduction

Comment: Consider breaking this introduction into shorter paragraphs to improve readability and emphasize key ideas, such as the health risks of loneliness, societal trends, and intervention strategies.

Comment: The number of citations in the first paragraph is quite dense. Consider integrating the references more smoothly to avoid overwhelming the reader and to improve narrative flow.

Comment: Strengthen the transition between global trends and the specific case of Iran. For example, a sentence explicitly linking the global phenomenon to Iran’s demographic shifts would improve the logical continuity.

Comment: While the background is comprehensive, clarify earlier why a long-term follow-up of the HoSIP program is necessary and what gap it addresses in current literature.

Comment: When referencing "various interventions" globally, it would be helpful to briefly name a few types (e.g., befriending programs, telehealth-based support) to give readers a clearer idea of what has been tried.

Comment: The final paragraph introduces your study, but the specific research question or hypothesis is not fully clear. Consider adding a sentence like: “This study aims to evaluate whether the effects of the HoSIP program are sustained two years after completion.”

Comment: The phrase “older adults” is consistently used, which is good. Ensure the same terminology is used throughout the paper, and avoid switching to "elderly" or “seniors” unless quoting from other sources.

Method

Comment: The phrase “This mixed method study with a concurrent nested embedded design” is technically accurate, but could be clarified for broader readability. Consider briefly describing what is "embedded" in what — e.g., “a primarily quantitative study with a qualitative component embedded for deeper exploration.”

Comment: The recruitment period is described with the exact dates. Consider aligning this level of specificity with the rest of the timeline (e.g., start and end dates of the intervention) for consistency and clarity.

Comment: The sentence “16 participants (Of the 36 lonely older adults...)” needs refinement in grammar and structure. Consider rephrasing as: “Out of the 36 older adults who originally participated in HoSIP, 16 remained in the follow-up phase and were contacted for this study.”

Comment: The long list of scales makes the paragraph heavy. You could introduce them with a sentence like: “Validated instruments were used to measure key variables, including loneliness, social support, psychological well-being, and self-care ability.” Then list them in smoother format, possibly in a bullet point or table format in the appendix.

Comment: Consider briefly explaining how the interview guide was developed. Was it based on previous literature, theoretical models, or pilot testing?

Comment: You could clarify how categories and subcategories were developed — was it inductive or deductive content analysis? That would help readers understand your analytic strategy.

Comment: Mentioning COREQ is excellent. Consider explicitly stating that the checklist guided both the design and reporting of the qualitative component for transparency.

Discussion

Comment: The opening sentence of the Discussion is long and slightly unclear. Consider breaking it into two: one describing the HoSIP program and another summarizing its long-term effects more clearly.

Comment: Good integration of functional theory and digital aging. Consider making the theoretical linkages even more explicit — e.g., how does this support or extend the theory, not just echo it?

Comment: The paragraph discussing quality of life and self-confidence would be stronger if you clearly stated the transition: e.g., “In addition to social benefits, psychological improvements such as self-confidence were also reported.”

Comment: In the paragraph starting “These findings provide the following insights…”, consider numbering or bulleting the insights (1, 2, 3, etc.) for clarity and easier reading. Each insight is important but gets lost in the long paragraph.

Comment: The Conclusion nicely summarizes the findings. You could enhance it by adding: “This model could serve as a blueprint for aging policies and community health strategies in other middle-income countries.”

Reviewer #2: This paper makes a meaningful contribution to the field, though some methodological concerns should be addressed.

Introduction

-This manuscript aims to evaluate the long-term effects of the HoSIP intervention and serves as a follow-up to the authors’ previous publication. The purpose of the study is not well stated. Was the study aimed at assessing the sustainability of the intervention after it was discontinued after two years? Or is the intervention still ongoing?

Method

-While the manuscript is well-referenced, the Methods section lacks sufficient detail. In particular, the description of the intervention is unclear. As, mentioned, it is not specified whether the intervention is ongoing or if it was limited to the initial 12-week period. Clarification is needed on whether this study is assessing the sustainability of the intervention's effects two years after its conclusion, or if the intervention has continued in some form during that time. Since the stated aim of the study is to examine the sustainability of the intervention, a more explicit explanation of the timeline and implementation status is essential.

-Additionally, the data analysis section requires further elaboration. Although the Results section lists the statistical tests used, it does not clearly indicate what comparisons were made or what hypotheses were being tested. Providing this context would greatly enhance the interpretability and rigor of the findings.

-Please structure the Methods section with appropriate subheadings for clarity.

Results

-Do you mean by RMANOVA, "Repeated Measures Analysis of Variance"? Please clarify.

-The limited sample size of intervention phase (n = 16) raises concerns about the statistical power and generalizability of the study's findings!!! In the discussion section, please address how the small sample size may have influenced your findings and clarify how this limitation should inform the interpretation of your results.

-In qualitative research, sample size is typically determined by the principle of theoretical saturation. However, in this study, the inclusion of 16 participants appears to have been driven primarily by the number of individuals involved in the intervention phase, rather than by saturation criteria.

-The alignment between the interview questions and the reported findings requires further clarification. Specifically, the questioning guide includes prompts about both positive and negative aspects of the program (e.g., perceived barriers, potential negative contributions from newly-joined participants). However, the extracted themes presented in the results section appear to focus exclusively on positive outcomes. This raises concerns about whether the analysis fully captured the range of participant responses or if negative perspectives were underrepresented or omitted. Clarify whether any negative or critical responses were provided by participants and, if so, explain how these were handled during the thematic analysis. If no negative themes emerged, consider discussing this in the limitations or discussion section, including possible reasons (e.g., social desirability bias, group dynamics). Ensure that the themes accurately reflect the scope of the questions asked and the diversity of participant perspectives.

-The final section of the results includes two parts—'Engagement and Expansion' and 'Challenges and Adjustments.' It is unclear whether these are intended as results of the study, and if so, whether they are based on quantitative or qualitative data. Since these sections primarily describe the intervention process and group conditions, their placement within the results may be confusing to readers. It may be more appropriate to relocate this content to the methodology or discussion sections, where it can be contextualized more effectively.

Discussion

-While the effectiveness of interventions in reducing social isolation among older adults has been well-documented, the distinctive strength of the present study lies in the sustained impact of the intervention observed over a two-year period. This long-term effectiveness is a significant contribution and should be emphasized consistently throughout the manuscript, particularly in the discussion section.

-The discussion section would benefit from a more thorough and transparent acknowledgment of the study’s methodological limitations. Currently, the limitations are either briefly mentioned or not addressed in sufficient depth. Given the nature of the study, several methodological constraints—such as small sample size, lack of control group, potential biases, limited generalizability—should be explicitly discussed.

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Reviewer #1: No

Reviewer #2: No

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Evaluating the Sustainability and Long-Term Outcomes of the Home Care Support Intervention Program (HoSIP) to Reduce Loneliness among Community-dwelling Older Adults:  A two-year follow-up study

PONE-D-25-08918R1

Dear Dr. Nadrian,

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.

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Kind regards,

Mehdi Rezaei

Academic Editor

PLOS ONE

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