Author's response to reviews

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1 Author's response to reviews Title:Musculoskeletal pain in Arctic indigenous and non-indigenous adolescents, prevalence and associations with psychosocial factors: A population-based study. Authors: Christian Eckhoff (eckhoff.christian@gmail.com) Siv Kvernmo (siv.kvernmo@uit.no) Version:2Date:20 May 2014 Author's response to reviews: see over

2 Christian Eckhoff, MD Department of Child and Adolescent Psychiatry, Division of Child and Adolescent Health, University Hospital North Norway Postbox 43 N-9038 Tromsoe Norway Natalie Pafitis MSc Executive Editor BMC Public Health BMC-series Journals BioMed Central Floor 6, 236 Gray's Inn Road London, WC1X 8HL Dear Editor, Please find enclosed the revised manuscript by Christian Eckhoff and Siv Kvernmo: Musculoskeletal pain in Arctic indigenous and non-indigenous adolescents, prevalence and associations with psychosocial factors: A population-based study. First, we thank the editor for the opportunity to resubmit our manuscript. We thank the two referees for their constructive comments, which have helped us improve the manuscript. Below, we address all comments point-by-point, discussing the subsequent modifications. All changes have been incorporated with line numbers referring to the revised manuscript. General comment: The addition of sedentary activity, due to comment by referee nr 1, has resulted in changes in the multivariable linear regression analyses presented in Table 3-5. Except for the contribution of sedentary activity to the models (commented below), the specific changes in beta values for the other associating factors were minimal. General improvements to the abstract, in line with the comments by the referees, have also been done. Referee 1: 1. Headache have been included in musculoskeletal (MS) pains. However, I think that headache is primarily a neurological condition that often co-exist with MS pain. Previous literature has not typically included headache in MS pains. I think you should at least discuss this in manuscript. We agree that headache as a symptom belongs to the field of neurology based on its location, prevalence in neurological conditions, and medical tradition. The justification for the inclusion is its co-existence with MS and the emphasis on widespread or multisite pain in relation to psychosocial problems. Furthermore, the most prevalent headache type is tension-type headache, and the prevalence of

3 headache as a complaint is much higher than the prevalence of migraine in adolescents, which is 5-10% approximately (ref. in revised text). The following changes to the text has been made: Headache was included based on its frequent co-existence with musculoskeletal pain. Tension-type headache, the most common form of headache, and musculoskeletal pain have shared mechanisms and risk factors [26]. Headache, as a complaint, is much more common than migraine in adolescents (5-10% prevalence) [27-29]. (Lines ) 2. In the studies by Paananen et al., multiple MS pains were associated with high sitting time (but not with low PA levels). Do you have data on amount of time spent sitting? The questionnaire had a question on sedentary activity fairly similar to that of Paananen et al. (2010) and the analyses were included in the revised manuscript. The univariate analysis is presented in the results in the text. In addition, sedentary activity made a significant contribution to the final linear regression model in the total sample, non-sami group, and in the functional impairment group. The inclusion of sedentary activity gave new interesting findings, which we are grateful for. The following changes were made: Changes to methods: Sedentary activity was measured by the question: After school hours: How many hours per school day (Monday to Friday) do you spend in front of TV, video, and/or PC? ; up to one hour (1), 1-2 (2), 3-5 (3), or >5 hours (4). (Lines ) Changes to results: Sedentary activity was significantly associated with the number of pain sites (p<.001), and physical activity for females only (p=.002). Post hoc analyses for sedentary activity in the total sample showed that those reporting >5 hours (M=1.60) of sedentary activity reported significantly more pain sites than those reporting 1-2 hours (M=1.37) and <1 hour (M=1.37), but not 3-5 hours (M=1.47). (Lines ) Summary of changes to the tables: Table 3-5: Sedentary activity made a significant contribution to the final linear regression model for the total sample (Table 3), the non-sami group (Table 4), and the functional impairment group (Table 5). Changes to the discussion: The finding that sedentary activity was associated with musculoskeletal pain in both genders supports Paananen et al. who found it associated with high sitting time. Hoftun et. al. who found it significant only in females [11]. Sedentary activity had a stronger association to musculoskeletal pain compared to low physical activity, which we found significant in females in the univariate analysis. This is in contrast to Hoftun et al. who found it so in both genders [11] and to Paananen et al. who found high physical activity to be associated with musculoskeletal pain [9]. (Lines ) Referee 2: Introduction:

4 1. The introduction is very brief and does not provide a clear rationale for the paper. The authors mention there are no published reports on indigenous groups, while there are an increasing number of papers on the prevalence of pain among African groups (adults and adolescents). The vast majority of African peoples can be considered to be "indigenous" in the sense that they have originated from that continent. I can refer the authors to Louw et al (2007) published in BMC and an update of this review is currently in progress. Once the authors have reviewed the existing database, they need to reconsider their claim stated in the introduction. The introduction was brief and general changes to improve the flow have been done (not shown in the cover letter). We have tried to improve the rationale for the article in each paragraph, highlighting this in the last sentences of the paragraphs, and leading up to the aims in the last paragraph of the introduction. Regarding pain studies on indigenous groups we still claim that there are few studies on physical pain among indigenous adolescents, and none in Arctic indigenous adolescent groups. We agree with the referee that the vast majority of African peoples can be seen as indigenous based on aboriginality. However, with respect to the characteristics of indigenous groups we have applied the modern analytical understanding of the characteristics of indigenous peoples, as described by the African Commission on Human and Peoples Rights (ACHPR) and the United Nations (UN). We refer to the following texts: The Netherlands Centre for Indigenous Peoples: o The African Commission on Human and Peoples Rights (ACHPR) work on indigenous peoples in Africa (International Work Group for Indigenous Affairs): o The following texts by the United Nations (UN): o &cd=1&cad=rja&uact=8&ved=0cckqfjaa&url=http%3a%2 F%2Fwhc.unesco.org%2Fdocument%2F9477&ei=sv11UiAHuaSywPijoDICg&usg=AFQjCNFR6UOY3kNkte2cIuVyxb DgLVHCMA&bvm=bv ,d.bGQ o &cd=2&ved=0cdeqfjab&url=http%3a%2f%2fwww.un.org %2Fesa%2Fsocdev%2Funpfii%2Fdocuments%2Fworkshop_da ta_background.doc&ei=sv11uiahuasywpijodicg&usg=afqjcnfmb2ln4aquefkk_8ozg uem8lvcyw&bvm=bv ,d.bgq N Ohenjo, R Willis, D Jackson, C Nettleton, K Good, B Mugarura. Indigenous health 3 health of indigenous people in Africa. Lancet. 2006;367(9526): o Kvernmo S: Indigenous peoples. In The Cambridge Handbook of Acculturation Psychology. Edited by Sam D, Berry J. Cambridge University Press, Cambridge; 2006:

5 In addition, we examined the articles in the review to Louw et al. (2007) to see if any of the critical appraised articles had looked at indigenous groups in line with the list and characteristics given by the ACHPR. We were not able to detect such findings. In light of these statements we still found it best to reconsider our claim, and modify it to Arctic indigenous adolescent groups. To our knowledge there are no published report on adolescent indigenous groups in the Arctic, which we have clarified in the manuscript. Also, we highlighted the indigenous aspect more in the introduction as pointed out by the referee. The following changes were made: Few studies have examined ethnic/cultural differences in physical pain and the association with psychosocial factors [1, 21]. Indigenous peoples have historically experienced several psychosocial traumas through harsh assimilation processes resulting in loss of ethnic identity, native language, land and traditional living conditions [22]. Lifetime PTSD has been found associated with pain in rural American Indians [23]. Pain studies on Sami, the indigenous population in Scandinavia, or other Arctic indigenous adolescent groups has not been done to our knowledge. A recent study have shown that Sami adolescents are not reporting more mental health problems than their majority Norwegian peers [24]. The attachment to harsh natural environments and hard physical work such as hunting, and primary industries like fishing and reindeer herding, may have influenced the Arctic indigenous peoples awareness of the body and perception of pain differently from their non-indigenous counterparts. (Lines 84-95) 2. The aim of the study should be clarified. The aim is to explore the prevalence of pain in multiethnic adolescents, but the analysis is based on establishing of there are differences between ethnic groups. Therefore, the authors should be more explicit about the primary objectives of the paper. The primary objectives have been clarified more clearly in the last paragraph of the introduction. The following changes have been made: The aim of the study was first to explore the prevalence of widespread musculoskeletal pain in indigenous and non-indigenous Arctic adolescents. Second, to examine the association with physical-, psychosocial factors, and mental health problems in a hierarchical model to determine the importance of the factors. Third, to examine the influence of pain related functional impairment on this association. (Lines ) 3. The construction of the introduction in general is poor and should be revised considerably. Paragraphs are short, does not flow into a logical argument and some factual information may not be correct (as indicated above). General improvements on the language and flow of the introduction have been made, though we still have tried to take space management into account (not sited here). The factual information is commented above in point The background should clearly outline the contribution of this paper to the current knowledge base (currently, the study findings do not indicate any new contribution to knowledge). This is a major revision to be addressed by the authors. The aims of the paper have been more clearly stated to show the contribution of this manuscript, and the rationale for the study aims have been highlighted more in the last

6 sentence in each paragraph of the introduction. We are not the first to examine widespread or multiple pain in adolescents, which is the main topic, but the amount of research is still not abundant. Furthermore, we believe, as Paananen et al. (2010) that the role of psychosocial factors is stronger in widespread in contrast to localized pain. This has been more clearly stated at the end of the first paragraph in the background. In addition, we have put more emphasis on the indigenous aspect in the introduction, as discussed above. Confirming other findings is a necessary part of research. To our knowledge there are no previous papers on musculoskeletal pain in Arctic indigenous adolescents. The hierarchical examination of relevant factors to determine their importance is also an important contribution. Lastly, the inclusion of a functional impairment measure is also a contribution of importance. Methods: 5. A main concern is that the data was collected more about 8-10 years ago and some of the statistics reported may not even be accurate or relevant. This can obviously not be addressed at this stage and the editor should make a decision, based on the policy of this journal. The Norwegian society is very stable and we have no reason to believe that studies done in the in Norway should not be representable to this date. It can be hypothesized that there might be a minor increase in adolescent complaints due to an increased pressure to succeed in the Norwegian society. To further address this question we found a short Norwegian report from the county of Hedmark in 2009 (no published article) where they asked the same questions for pain and used the HSCL-10 for anxiety/depression. N=1336 and the RR=78%. The prevalence of headache was 57.5% to our 50.75%, neck/shoulder 36.5% to 35.2%, back pain 38% to 34%, and anxiety/depression 25% to our 19.1%. Link to Norwegian report labeled Resultater ungdomsundersøkelsene i Hedmark 2009 : Secondly, and most importantly, the primary goal of this article was the study of predictors. Thus one can be less strict on the time aspect in contradiction to a pure prevalence study on disease. To conclude: we think the data still is representable and relevant for the Arctic adolescent population in Norwegian and Scandinavian population. 6. There is no information about the design of the questionnaire although the variables collected were described. The design is based on previous questionnaire studies conducted by the Norwegian Institute of Public Health. More information about the Youth Studies can be found at their webpage: The link has been included as a reference in the methods: The Norwegian Arctic Adolescent Health Study [25] was conducted among 10 th graders (15-16 year olds) in all junior high schools in the three northernmost counties in Norway, in (Lines ) 7. There is no information on content validity or reliability (I note that Chronbach Alpha values were reported).

7 Where able, we have given references for validated instruments. There are references in the text to the Hopkins Symptom Checklist-10 (HSCL-10), the Strengths and Difficulties Questionnaire (SDQ), the General perceived self-efficacy scale, and the Parental involvement Scale. Though a shorter version for the General perceived selfefficacy scale and the Parental Involvement Scale were used. We are aware of the shortcomings in replication of the results due to use of some instruments less common outside the studies by the Norwegian Institute of Public Health s design. We consider the reliability of the different Norwegian Institute of Public Health studies as good, due to similar questionnaires and comparable results (ref. in text e.g. Lien et al. and Sagatun et al.). 8. More information and justification is required e.g. why was a 12 month recall needed and what is meant with pain several times. What is the rationale for considering four sites as widespread pain? Why were other factors such as duration, why was the intensity of pain/treatment received not considered? A major limitation is the recall period, lack of specified duration, and intensity which results in a poor measure objectively. This is mentioned in the first draft. The authors did not design the main part of the questionnaire, where these questions were included, and are aware of its limitations on this point. Still, pain is a subjective experience and we don t consider the pain questions as useless. There have been previous publications with similar construction. We support that there should be a consensus on subjective musculoskeletal pain questions in future studies. The pain questions presented in the study of Hoftun et al. (2008) are becoming more common, and are better objective measures. For widespread pain, we did not make a cut off at four pain sites. The musculoskeletal pain variable was handled as a discrete variable ranging from 0-4 pain sites, as stated in the original manuscript. This was to emphasize the dose-response relationship between increasing musculoskeletal pains and psychosocial problems. It also gives greater statistical power to the analyses than pooling of pain sites into groups. If more relevant pain sites had been asked for we would have incorporated them. Previous papers have considered more than single site pain as widespread or multiple pains, but this is of course also subjective and up for debate. 9. Why was functional impairment limited to reduced activity during leisure time and how was leisure time defined (e.g. Was sport included in leisure time). In Norway, organized sports are not part of the school program as in e.g. the USA, but organized by private teams during leisure time. Thus, it is normal for Norwegians to consider organized sports a part of leisure time. Activity not incorporated in leisure time is physical education, which in Norwegian schools usually is limited to two hours per week. One exception is very few specialized high schools for athletes where they have training incorporated in the school hours. 10. The questionnaire seems to be quite long- how long did it take to complete? In the submitted manuscript it was stated that the questionnaire was completed during two school hours. In other words the adolescents had 90 minutes to complete the questionnaire, but few used more than minutes. The following changes were made: The questionnaires were administered in classroom settings, monitored by project

8 staff, and completed during two school hours. Few students used more than minutes. (Lines ) Data analysis and results: 11. The analysis is dependent on the primary question and the analysis should then be clarified to address the main question. If the aim was to establish difference between ethnic groups, further analysis to explore this specific question should be done. While the difference in prevalence and number of pain sites were analysed between the Sami and non-sami groups the issue of whether the predictors are the same for the Sami and non-same groups was not explored (which is actually the potential gap in knowledge which can be addressed). Although the authors stated that the sami and none-sami groups were similar, the data were not reported. Instead, pain related functional impairment in relation to associated factors were reported in detail (table 4) while this was not a primary objective of the paper. The results from the Sami vs. non-sami group regression analyses were reported in the text in the original manuscript. The non-sami group results, naturally being the majority of the sample, did not differ much from the total sample and only the differences of anxiety/depression and Conduct problems were reported. Otherwise we referred to the values of the total sample in Table 3 that were the same. We thought the reader could use Table 3 as a reference to the results presented in the text. A factor in this decision was space management. The regression model and the beta values of the significant factors for the Sami group were reported in the text. There were some differences that also were commented in the discussion, but we were hesitant to call these major differences due to the difference in power between the two groups. In retrospect we understand that it was hard for the reader to follow these findings. To address this we have made the following changes: - To highlight ethnic differences more we stratified Table 1 by Sami and non-sami first and then by gender. - We included a new Table 4 were we report only the final regression model (hierarchical step 4) for the Sami and non-sami groups. Following the same steps as Table 3. This is described in the text. See Table 4 in the revised manuscript. - We cut down the functional impairment regression model (the old Table 4) into just the final model as for the Sami vs. non-sami. This is now Table 5. See Table 5 in the revised manuscript. The choice of only reporting the final model is based on it being the most interesting, other factors are highlighted in Table 3, and due to space management. That the same steps as in Table 3 have been followed in Table 4-5 is highlighted in the footnote of the tables and in the method section under data analysis: All stratified regression analyses followed the subsequent steps: (Line 221 in the method section) 12. It is difficult to read the results (particularly in relation to the objectives, which are also unclear). Some data are not reported, although stated as a narrative). Readers will find it very difficult to follow the findings as reported. The results

9 section must be aligned according to the main purpose and reported accordingly. We agree that the results section were difficult to follow. General improvements in relation to objectives and flow have been carried out (changes not shown in the cover letter). We think it is easier for the reader to follow the univariate findings first, with the specifications in Table 1-2, and then follow the multivariate findings with specifications in Tables 3-5. The response to point 11 also addresses this issue. Discussion: 13. The discussion highlights that there are many studies with similar findings (hence the need for this study must be explained). This has been discussed in earlier points with general improvements to the background and especially clarification of the study aims. In addition, we have added a main findings subheading at the start of the discussion where we have highlighted the main findings. We also added the subheading of comparisons to previous studies, in addition to the subheadings already present, to improve the structure and readability. In addition, the paragraph on the indigenous results has been moved up in the discussion to highlight this at an earlier stage. There are the previous studies on the association between pain and mental health (depression and anxiety). Not all of these, which are referred to in the discussion, have looked at widespread or multisite pain, and some have only looked at the association with depression/anxiety. 14. Some of the findings must be checked e.g. the authors state that the strongest factor associated with pain was anxiety followed by life events (when the results indicated that school stress was the second strongest factor). These issues must be checked and corrected. First, due to the inclusion of sedentary activity to the models, the results has been checked and confirmed. In the original text we highlighted the results from the final linear regression model for the total sample where anxiety/depression (β=.23**) were followed by Negative life events (β=.13**) and School-related stress (β=.12**). This was not clearly stated in the text and resulted in unnecessary confusion for the reader. This has been specified and where needed the results highlighted in the text following the successive order. Following changes were made: For the total sample anxiety/depression was the strongest factor, followed by negative life events and school-related stress. (Lines ) 15. In the conclusion the authors alluded to the dose response they found between pain and psychological factors (which may not be the primary aim, albeit this is also not clear). Ethnic difference was merely mentioned with no explanation or implications. The last sentence of the study weakness and strength is perhaps the focus and strength of the paper and this focus should be maintained and justified throughout the manuscript. The clarification of the aims has been discussed earlier in the cover letter. The ethnic difference has been emphasized more clearly and moved to the start of the conclusion. The following changes were made: We found no significant difference in the prevalence of widespread pain between

10 indigenous Sami and their majority Norwegian peers, but some differences in the multivariable analyses of associating factors. The most important sociocultural aspect of the findings is that the indigenous Sami are not worse off. We found a strong doseresponse association between widespread musculoskeletal pain and psychosocial factors Anxiety/depression, negative life events, and school-related stress were the most important factors associated with musculoskeletal pain, especially in those reporting pain related functional impairment. (Lines ) Additional corrections: Together with the revision of the manuscript the statistics has been reviewed. There is one correction in the results were the correct explained variance for anxiety/depression in the final multivariable model is 3.0%, not 4.8%. The following changes were made to the text: In the final model, anxiety/depression, negative life events and school-related stress were the strongest factors associated with musculoskeletal pain for both genders, with anxiety/depression as the single factor explaining most of the variance (3.0%) in the total sample. (Lines ) Both authors have approved the revised manuscript and fulfill the Vancouver requirements for authorship. Thank you for considering our manuscript for publication as a research article in BMC Public Health. We look forward to your response. Sincerely, Christian Eckhoff Lead author MD/PhD student Department of Child and Adolescent Psychiatry, Division of Child and Adolescent Health, University Hospital North Norway