Association Between Floor of Residence and Frailty in Walk-Up Buildings Among Functionally Independent Older Adults: A Cross-Sectional Study

Response to Reviewer 1 Comments

1. Summary

Thank you very much for taking the time to review our manuscript. We have carefully considered and addressed all comments raised by the reviewers. All revisions have been made using the “Track Changes” function in Microsoft Word. Please find the detailed responses below and the corresponding revisions highlighted in the re-submitted files.

2. Questions for General Evaluation

Reviewer’s Evaluation

Does the introduction provide sufficient background and include all relevant references?

Yes

Is the research design appropriate?

Yes

Are the methods adequately described?

Can be improved

Are the results clearly presented?

Must be improved

Are the conclusions supported by the results?

Must be improved

Are all figures and tables clear and well-presented?

Not applicable

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: Tables 2 and 3 should report values as n (%) for both groups. In addition, age is reported for only one group using an odds ratio (OR). This may reflect a misunderstanding between the regression coefficient (B) and Exp(B). Please clarify and revise accordingly.

Response 1: Thank you for this comment. We apologize for any confusion caused by the original table presentation. Regarding the reporting of group-specific sample sizes for categorical variables, these descriptive statistics are presented in Table 1. However, we agree that the original format of Table 1 made it difficult to identify the number of participants in each category. Therefore, we have revised Table 1 to explicitly report n (%) for each subgroup, improving clarity and readability.

With respect to age, this variable was entered into the logistic regression models as a continuous variable, and the reported odds ratio represents the change in odds of frailty per one-year increase in age. The odds ratios reported in Tables 2 and 3 are therefore correctly presented. To avoid further misunderstanding, we have added the label “(continuous)” to age, floor of residence, and dietary variety score in Tables 2 and 3.

Comments 2: The forest plot should present a single odds ratio (OR) with a 95% confidence interval for each variable derived from the logistic regression model. However, two lines are reported for each variable. Please reconsider and revise the presentation to ensure that only one estimate per variable is shown.

Response 2: Thank you for this comment. We apologize that the purpose of the forest plot was not sufficiently clear in the previous version. The forest plot was not intended to display the results of a single multivariable logistic regression model, but rather to illustrate the results of stratified analyses, showing the association between floor of residence and frailty within each predefined subgroup. Therefore, multiple estimates are presented for the same variable (floor of residence), corresponding to different subgroups, rather than multiple estimates derived from a single model.

To avoid further misunderstanding, we have revised the figure footnote to explicitly state that the forest plot presents subgroup-specific odds ratios stratified by age group, sex, IADL score, homebound status, living arrangement, and years of residence. No changes to the underlying analyses or estimates were required.

Comments 3: Table 2 and - How to identify for model fit

Response 3: Thank you for this comment. To clarify model performance, we evaluated the discrimination ability of each multivariable logistic regression model using the C-statistic (area under the receiver operating characteristic curve, AUC). The AUC values and corresponding 95% confidence intervals are reported in the Results section, demonstrating acceptable discrimination for both the KCL-defined and FS-defined frailty models. We have revised the Methods (Lines 157–159), Results (Lines 199–202), and the footnotes of Tables 2 and 3 accordingly to clearly describe this approach.