Author s response to reviews

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1 Author s response to reviews Title: Lifestyle-related factors that explain disaster-induced changes in socioeconomic status and poor subjective health: a cross-sectional study from the Fukushima Health Management Survey Authors: Masato Nagai (m-nagai@med.tohoku.ac.jp) Tetsuya Ohira (teoohira@fmu.ac.jp) Wen Zhang (zhangw09@fmu.ac.jp) Hironori Nakano (h-nakano@fmu.ac.jp) Masaharu Maeda (masagen@fmu.ac.jp) Seiji Yasumura (yasumura@fmu.ac.jp) Masafumi Abe (masafumi@fmu.ac.jp) Version: 2 Date: 20 Dec 2016 Author s response to reviews: COMMENTS OF THE REVIEWERS AND AUTHORS REPLIES Journal: BMC Public Health MS. Ref. No.: PUBH-D Title: Lifestyle-related factors that explain disaster-induced changes in socioeconomic status and poor subjective health: a cross-sectional study from Fukushima Health Management Survey Comments from Reviewer #3: 1. The topic is interesting but the hypothesis that what the authors refer to as change in socioeconomic status would affect life-styles such as smoking, exercise and alcohol consumption should be theoretically better underpinned citing the public health and behavioural literature to a higher extent. Furthermore, the time frame for such changes in health-related life-styles should at least be discussed, although this is a cross-sectional study.

2 As described in introduction, smoking, alcohol consumption, physical activity, and sleeping is associated with not only subjective health but also with SES[16-20]. Then, it is hypothesized that change to lower SES induces poor subjective health through lifestyle change. We added the sentence in the introduction section to clarify this hypothesis. Additionally, as described in discussion, even though it is considered that the worse lifestyle causes poor subjective health, the association between lifestyle and subjective health is bidirectional. The worse lifestyle induces poor subjective health, while there is possibility that poor subjective health also lead to worse lifestyle such as impaired quality of sleep and less social participation. Then we consider that the causality between lifestyle and subjective health should not be discussed any more. At least, change for the worse lifestyle and subjective health occurred after change in SES because the reason of change in SES was disasters and following evacuation in present study. We further added sentences in the introduction and discussion sections to explain our hypothesis, as follows. [P 5, Lines 49-59] Socioeconomic status (SES), which comprises variables such as working conditions, income, and education, is associated with subjective health [4 11]: low SES consistently results in poor subjective health. In addition to SES, lifestyle-related factors, such as smoking [7, 12], alcohol consumption [13], physical activity [7, 12, 13], and sleeping [14, 15] are determinant factors of subjective health. These factors are also associated with SES [16 20]. Thus, it is hypothesized that changes that lower SES induce poor subjective health through lifestyle changes. Importantly, disasters have a substantial impact on lifestyles and SES; changes in SES and latter lower subjective health are unavoidable, following a disaster. However, lifestyle-related factors are still modifiable. [P 16, Lines ] First, the present study design was cross-sectional. We did not have any information about SES, lifestyles, or subjective health of the participants before the disaster. Thus, we could not confirm the causality between explanatory factors and subjective health. Lifestyle modification as an

3 intervention does not necessarily prevent poor subjective health owing to a change in SES. However, in the present study, the reason for change in SES was a natural disaster, followed by widespread evacuations. We argue that negative changes in lifestyle and subjective health occurred after the changes in SES. 2. Another important issue concerns the authors' use of the notion "changes in socioeconomic status" due to a calamity such as the one that occurred in Fukushima. The common definition in the literature of socioeconomic status is that it concerns occupation, education and income. It is clear that the education of the individual will not change at all due to a calamity such as the one that occurred in Fukushima. It is also probable that income will not change for most people in an economically developed welfare society such as Japan, and occupation will not change but the active use of one's occupation will probably be disrupted during a restricted time period. The authors use the phrasing "changes in socioeconomic status" to denote change in housing etc. during a restricted time frame, and there should be a discussion regarding to what extent this is a change in socioeconomic status according to the common definitions of socioeconomic status. As you indicated, socioeconomic status is mainly defined by occupation, education, and income, and disaster did not have effect of change in education status. So, we did not define education status as socioeconomic status and deal with education status as exposure in present study. Additionally, socioeconomic status is composite indicator which is defined by occupation, education, and income and we also included living arrangement in socioeconomic status in present study. Then, to clarify that present result is also showed by each socioeconomic factor, we conducted further analysis about each socioeconomic factor in Supplement tables. In this analysis, we confirmed same tendency between the result of composite socioeconomic status and its each factor. Also, although victims have received accident compensation, Supplemental table 2 showed that 18.1% in men and 27.1% in women became unemployed and 26.2% in men and 17.6% in women decreased income.

4 3. Another main problem with the manuscript is the low participation rate (40.7%), which is even lower than that in the final analyses due to the restrictions the authors have to make. The risk of selection bias, i.e. that the strengths and directions of associations in the parameter population are not reflected correctly in the final sample, increases with decreasing participation rate. The authors discuss selection bias very shortly as one of four weaknesses at the end of the discussion, but they should discuss the possible effects of selection bias on the strengths and directions of the associations observed related to the true strengths and directions in the parameter population. The issue of the low participation rate and risk of selection bias is maybe the most important weakness of this study. Thank you for your important comment. As with previously response, the prevalence of poor subjective health in 43,364 participants aged years before exclusion is 15.5% in men and 17.1% in women. After exclusion, it is 14.8% in men and 15.8% in women. There is not greater difference between with and without exclusion. Therefore, we consider that the effect of selection bias is small. However, we could not evaluate about response bias. Because there is no basic data about change in SES, lifestyle habit, and subjective health in non-respondent. We can consider both possibilities: that participants with poor subjective health tend to not respond because they were down and/or that participants with good subjective health tend to not respond because they do not have any problems. We added sentences concerning the selection and response bias in the discussion section, as follows. [P 16, Lines 276- P 17, Lines 288] Second, the response rate was only 40.7%. Additionally, we excluded 23.1% of respondents aged years. The results of this study may thus be affected by response and selection bias. However, the difference in prevalence of poor subjective health between participants with and without the exclusions, was only 0.7 percent point for men and 1.3 percent point for women. Therefore, we consider the effect of selection bias small. Importantly, we could not evaluate the response bias because there was no basic data about change in SES, lifestyle habits, and subjective health for non-respondents. We acknowledge both following possibilities: that

5 participants with poor subjective health tend not to respond because they are feeling down or unwell, and/or that participants with good subjective health tend not to respond because they do not have any problems. These may have led to an overestimate or underestimate of the impact of lifestyle-related factors on the associations between change in SES and poor subjective health. 4. All tables should give full information concerning time (when was the study conducted?), place (where was the study conducted?) and person (define the population according to age range, gender, numbers and, if possible, the name of the study population). Thank you for your important comment. We included your suggested information in titles as follows: among 14,913 men and 18,437 women aged years in Fukushima Health Management Survey, Fukushima, Please, see Tables and Supply mental Tables. The issue of clarity and grammatical correctness is important, and the manuscript should be generally improved accordingly. Thank you for your important comment. Our manuscript was checked by English editing service.

6 5. Please discuss the fact that the data are self-reported, as well as the validity of some of the variables concerning for instance what the authors denote as "change in socioeconomic status" as well as mediating variables such as the quality of the ability to sleep. Have these variables been used previously in the international literature? Thank you for your important comment. As you indicated, information about exposure and mediators was obtained from self-reported in present study. However, subjective health, present outcome, is originally index which is assessed by subjective and self-reported. It is possibility that not objectively measured but self-reported status are more associated with subjective health. If people who have actually and objectively good sleep dissatisfied own sleep, they would report poor in own subjective health. Then although exposure and mediators were self-reported, modifying self-reported conditions may be more important and useful than objectively measured ones. We described the same word and query about lifestyle based on the survey questionnaire. [P 17, Lines 290-P 18, Lines 296] However, subjective health is an index that assesses subjective and self-reported. Thus, not objectively measured but self-reported status is more associated with subjective health. For example, if people who have good sleep, as measured objectively, are dissatisfied with their own sleep, they will likely report poor in own subjective health. Thus, even though exposure and mediators are self-reported, modifying self-reported conditions will arguably be more important and useful than focusing on objectively measured ones. 6. Why do the authors use Poisson regression models in their statistical analyses? Please give the rationale.

7 It is well known that odds ratio does not approximate to and overestimate of relative risk (prevalence ratio) when prevalence of outcome is 10% (Barros AJ, et al. BMC Med Res Methodol 2003, Zhang J, et al. JAMA 1998). Then, to estimate approximate prevalence ratio, we used method of references cited (Spiegelman D, et al. Am J Epidemiol 2005). Editorial Requests 1. Please include a 'Conclusions' section heading for your concluding paragraph We included a Conclusions section. [P 19, Lines 301] CONCLUSIONS (2) Please provide a full Declarations section in your manuscript as detailed here: We included a declarations based on suggested submission-guidelines.

8 [P 19, Lines 317-P 20, Lines 342] Acknowledgements The findings and conclusions of this article are solely the responsibility of the authors and do not represent the official views of Fukushima Prefecture government. Funding This survey was partly supported by the National Health Fund for Children and Adults Affected by the Nuclear Incident. Competing Interest The authors declare that they have no conflicts of interest. Authors Contribution MN and TO contributed to the design of the study. TO, MM, SY, and MA participated in data collection. MN participated in data analysis. MN and TO participated in writing the report. TO, WZ, HN, MM, SY, and MA participated in critical revision of the manuscript. All authors approve the final version of the report for submission. Availability of data and materials No additional data available.

9 Ethics approval and consent to participate The study protocol was approved by the Ethics Committee of Fukushima Medical University. Participants who returned the self-administered questionnaires were considered to have consented to participate. Consent for publication Not applicable.