Estimating psychophysiological loads by repeated temperature steps on humans using a state–space model

Miho Iwasaki; Yusuke Morito; Kyosuke Watanabe; Kiyoshi Kuroi; Shota Hori; Yoko Sakata; Kei Mizuno; Kazunobu Okazaki; Yasuyoshi Watanabe

doi:10.1371/journal.pone.0335545

Peer Review History

Original SubmissionMarch 5, 2025
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If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references.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 If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice. Additional Editor Comments: Linking daily temperature variations between indoors and outdoors to health is pertinent worldwide. The study requires significant adjustments because its current methodology is very constrained 1) sample size specially when it addresses psychophysiological burdens. The planned study is fine, however the physical exhaustion scale is too broad (0–100), making assessments more arbitrary. One reviewer has rightly suggested that tests such as as skin temperature, ECG, HR, and HRV, factors like activity and sleep (including latency, inertia, and duration of sleep) could be taken into account. I suggest you rework on methodological errors to improve current form of manuscript. Study limitations should be adequately mentioned under relevant headings. [Note: HTML markup is below. Please do not edit.] 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 ******** 2. Has the statistical analysis been performed appropriately and rigorously? -->?> Reviewer #1: Yes Reviewer #2: Yes ****** 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 ****** 4. Is the manuscript presented in an intelligible fashion and written in standard English??> Reviewer #1: Yes Reviewer #2: Yes ****** Reviewer #1: Despite the insufficient sample size, the study design was sound and thoroughly examined. We recommend conducting this study over a longer period of time and with a larger sample size in order to examine the physiological and psychological impacts of several successive temperature increments. Reviewer #2: The wordwide exposure of the humans exposed to daily temperature differences indoors and outdoors associated to health risks and fatigue is a thoughtful concept. The study needs phenomenal changes as the approach is quite limited/ narrow. The study aimed to clarify the psychophysiological loads by repeated short-term temperature differences on n = 28 (14 males and 14 females) Japanese individuals. The study planned is good, but of very short duration as the data collected for each test is of only 183 minutes for 4 times. First the duration of the study should be more, may be at least for a week or so, secondly, the effects should be recorded not only in the test duration but also pre and post test, to proove the case. The scale of physical fatigue is quite large (0-100), making the psychological measurements more subjective.Besides the psychophysiological and physiological measurements like HR, HRV, skin temperature and ECG, parameters like activity and sleep (latency, inertia and sleep duration) should also be considered. The statistics has been thoroghly performed, but is too complex to understand. The comparisons between the temperature- controlled and the treated groups would have made the study/ statistics simple and easy to prove. Overall the experimental design should be more elaborate in order to demonstrate good internal control and structure. However, the lack of contextual and participant-specific data, along with a few methodological omissions, has impacted the interpretability and external validity of the findings. ****** 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 Reviewer #2: No ******** [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/ . PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org https://doi.org/10.1371/journal.pone.0335545.r001
Revision 1
29 Aug 2025 Author Response Responses to Additional Editor Comments: [Part 1] Linking daily temperature variations between indoors and outdoors to health is pertinent worldwide. The study requires significant adjustments because its current methodology is very constrained 1) sample size specially when it addresses psychophysiological burdens. [Response] We sincerely thank the Editor for the thoughtful and constructive comments regarding our manuscript. As this study was conducted in a tightly controlled laboratory environment, our primary aim was to explore psychophysiological responses to short-term temperature changes under experimental conditions. We fully agree that further research with a larger sample size and in real-world environments will be essential to improve generalizability and assess broader health implications. To address this, we have added a Limitation section in the revised manuscript, where we discuss this issue in detail (see lines 418–430). [Part 2] The planned study is fine, however the physical exhaustion scale is too broad (0–100), making assessments more arbitrary. [Response] We thank the editor’s comment on the use of a 0–100 visual analogue scale (VAS) for assessing physical fatigue. The VAS is a widely used and validated tool for capturing subjective fatigue, as shown by Lee et al. (1991). Its continuous format allows for detecting subtle changes that may be missed by categorical scales, making it suitable for psychophysiological studies like ours. To minimize variability, we gave participants clear instructions with anchor definitions (0 = no fatigue, 100 = complete exhaustion) and ensured consistency across sessions. We have also revised the Methods section to better explain our use of the VAS (see lines 112–118). [Part 3] One reviewer has rightly suggested that tests such as as skin temperature, ECG, HR, and HRV, factors like activity and sleep (including latency, inertia, and duration of sleep) could be taken into account. I suggest you rework on methodological errors to improve current form of manuscript. Study limitations should be adequately mentioned under relevant headings. [Response] We thank the Editor for highlighting the importance of incorporating additional physiological and behavioral indicators such as skin temperature, ECG, HR, HRV, sleep parameters (latency, inertia, duration), and physical activity. We fully agree that these factors are essential for developing a more ecologically valid and comprehensive model of thermally induced fatigue in real-world settings. In the present study, our focus was to establish a baseline understanding of the psychophysiological burden under temperature step conditions in a controlled environment. Nevertheless, we acknowledge this limitation and have added corresponding statements in the new Limitation section of the revised manuscript to outline directions for future research (see lines 418–457). Responses to Reviewer #1 Reviewer #1’s comments: Despite the insufficient sample size, the study design was sound and thoroughly examined. We recommend conducting this study over a longer period of time and with a larger sample size in order to examine the physiological and psychological impacts of several successive temperature increments. [Response] We sincerely thank the reviewer for recognizing the strengths of our study design. We fully agree with the suggestion that conducting the study over a longer period and with a larger sample size would help clarify the physiological and psychological impacts of repeated temperature changes more robustly. As this study was designed as a preliminary investigation conducted under controlled laboratory conditions, we focused on establishing a basic psychophysiological response model. In the revised manuscript, we have now included a Limitation section discussing this point and emphasizing the need for future studies with extended duration and broader sample populations (see lines 418–457). Responses to Reviewer #2 Reviewer #2’s comments: The worldwide exposure of the humans exposed to daily temperature differences indoors and outdoors associated to health risks and fatigue is a thoughtful concept. The study needs phenomenal changes as the approach is quite limited/narrow. The study aimed to clarify the psychophysiological loads by repeated short-term temperature differences on n = 28 (14 males and 14 females) Japanese individuals. The study planned is good, but of very short duration as the data collected for each test is of only 183 minutes for 4 times. First the duration of the study should be more, may be at least for a week or so, secondly, the effects should be recorded not only in the test duration but also pre and post test, to prove the case. The scale of physical fatigue is quite large (0-100), making the psychological measurements more subjective. Besides the psychophysiological and physiological measurements like HR, HRV, skin temperature and ECG, parameters like activity and sleep (latency, inertia and sleep duration) should also be considered. The statistics has been thoroughly performed, but is too complex to understand. The comparisons between the temperature- controlled and the treated groups would have made the study/statistics simple and easy to prove. Overall the experimental design should be more elaborate in order to demonstrate good internal control and structure. However, the lack of contextual and participant-specific data, along with a few methodological omissions, has impacted the interpretability and external validity of the findings. [Response] We thank the reviewer for the thorough review of our manuscript. We sincerely appreciate for recognizing our research concept as "thoughtful" and for providing numerous constructive comments. We have addressed each of the concerns below and have made revisions throughout the manuscript based on your valuable feedback. 1. Study duration and measurement timing We appreciate the reviewer’s thoughtful comments regarding the limited study duration and measurement design. This study was conducted under controlled laboratory conditions with the aim of exploring short-term psychophysiological responses to temperature steps. We fully agree that longer-term studies with pre- and post-assessments, as well as real-world observations, are essential for future work. We have added a new Limitation section to the manuscript addressing this issue (see lines 418–430). 2. Use of VAS for fatigue assessment We thank the reviewer’s comment on the use of a 0–100 visual analogue scale (VAS) for assessing physical fatigue. The VAS is a widely used and validated tool for capturing subjective fatigue, as shown by Lee et al. (1991). Its continuous format allows for detecting subtle changes that may be missed by categorical scales, making it suitable for psychophysiological studies like ours. To minimize variability, we gave participants clear instructions with anchor definitions (0 = no fatigue, 100 = complete exhaustion) and ensured consistency across sessions. We have also revised the Methods section to better explain our use of the VAS (see lines 112–118). 3. Consideration of additional parameters such as sleep and activity We thank the reviewer for highlighting the importance of including additional physiological and behavioral factors such as activity and sleep (latency, inertia, and duration). We agree that incorporating these variables would enhance the ecological validity of future models. In this study, our focus was to establish a psychophysiological load model within a controlled setting. We have now noted the absence of these variables and the need for more comprehensive assessments in future studies in the Limitation section (see lines 431–437). 4. Statistical methodology We appreciate the reviewer’s feedback regarding the complexity of the statistical approach. To address our primary goal—capturing the temporal dynamics of psychophysiological load—we employed a Bayesian state-space model. This method is particularly suited for time-series data with repeated measures, where each observation is autocorrelated with prior states. Unlike conventional methods that assume independence between time points, the state-space model distinguishes between the latent internal state (e.g., underlying fatigue) and random observation noise, allowing us to track how participants’ internal states evolve over time. This approach provides a more accurate assessment of intervention effects than simple group-level comparisons at discrete time points. We also included a temperature-stable condition (26°C–26°C) as a control group for comparison. Attachments Attachment Submitted filename: Response To Reviewers_PONE-D-25-06325.docx https://doi.org/10.1371/journal.pone.0335545.r002
13 Oct 2025 Decision Letter - Neelu Jain Gupta, Editor Estimating Psychophysiological Loads by Repeated Temperature Steps on Humans using a State–Space Model PONE-D-25-06325R1 Dear Dr. Watanabe, 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. An invoice will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager® and clicking the ‘Update My Information' link at the top of the page. For questions related to billing, please contact billing support . If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Neelu Jain Gupta, Ph.D. Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: Reviewer's Responses to Questions Comments to the Author Reviewer #1: All comments have been addressed Reviewer #2: All comments have been addressed ******** 2. Is the manuscript technically sound, and do the data support the conclusions??> Reviewer #1: Yes Reviewer #2: Yes ****** 3. Has the statistical analysis been performed appropriately and rigorously? -->?> Reviewer #1: Yes Reviewer #2: Yes ****** 4. Have the authors made all data underlying the findings in their manuscript fully available??> The PLOS Data policy Reviewer #1: Yes Reviewer #2: Yes ****** 5. Is the manuscript presented in an intelligible fashion and written in standard English??> Reviewer #1: Yes Reviewer #2: Yes ****** Reviewer #1: The study effectively addresses a timely issue of repeated temperature changes and their psychophysiological impact using a robust Bayesian state–space modeling approach. The experimental design is well controlled and methodologically sound, though the small sample size (n=28) and short duration (183 minutes) limit broader generalization. i recommend authors the Inclusion of parameters such as sleep, activity, and circadian factors can enhance ecological validity in future studies. The Bayesian modeling is appropriate and insightful, but interpretations should remain cautious given laboratory constraints and limited real-world validation. Overall, the manuscript is clearly written, logically structured, and transparent about its limitations, with constructive directions for future research. Reviewer #2: These findings provide valuable insights that could contribute to the development of effective fatigue management strategies and the establishment of best practices to reduce adverse health effects from sudden and uncontrollable environmental temperature changes in daily life. I commend the authors for this important preliminary work and would encourage them to further strengthen it by addressing the limitations noted in the current study, while also underscoring the need for future investigations with longer durations and more diverse populations. ****** 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 Reviewer #2: Yes: Shalie Malik ******** https://doi.org/10.1371/journal.pone.0335545.r003
Formally Accepted
Acceptance Letter - Neelu Jain Gupta, Editor PONE-D-25-06325R1 PLOS ONE Dear Dr. Watanabe, I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now being handed over to our production team. At this stage, our production department will prepare your paper for publication. This includes ensuring the following: * All references, tables, and figures are properly cited * All relevant supporting information is included in the manuscript submission, * There are no issues that prevent the paper from being properly typeset You will receive further instructions from the production team, including instructions on how to review your proof when it is ready. Please keep in mind that we are working through a large volume of accepted articles, so please give us a few days to review your paper and let you know the next and final steps. Lastly, if your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. You will receive an invoice from PLOS for your publication fee after your manuscript has reached the completed accept phase. If you receive an email requesting payment before acceptance or for any other service, this may be a phishing scheme. Learn how to identify phishing emails and protect your accounts at https://explore.plos.org/phishing. If we can help with anything else, please email us at customercare@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Neelu Jain Gupta Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0335545.r004

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