Title: Mediators of the association between parental education and breakfast consumption among adolescents in Norway: the ESSENS study

Transcription

1 Author s response to reviews Title: Mediators of the association between parental education and breakfast consumption among adolescents in Norway: the ESSENS study Authors: Mekdes Gebremariam (mekdes.gebremariam@medisin.uio.no;mekdes-kebede.gebremariam@- hioa.noo) Sigrun Henjum (sigrun.henjum@hioa.no) Elisabeth Hurum (s294334@stud.hioa.no) Jorun Utne (s294216@stud.hioa.no) Laura Terragni (laura.terragni@hioa.no) Liv Elin Torheim (Liv.Elin.Torheim@hioa.no) Version: 1 Date: 16 Jan 2017 Author s response to reviews: Dear editor, We would like to thank the reviewers for their constructive comments, which we believe have helped improve the manuscript. We have addressed their comments one by one below. Best regards, Mekdes Gebremariam, corresponding author Reviewer #1: This is a cross-sectional study investigating breakfast consumption with parental education in adolescence, and whether this association is modified by related factors. It provides some interesting data and the modelling provides insight into potential mediators.

2 Please find section specific feedback below. Title: -Currently suggests socioeconomic differences however the study seems to only focus on parental education rather than SES - although they are related, they are not the same thing. We thank the reviewer for this comment. Indeed, SES and parental education are related, and parental education is one of the most important indicators of SES among youth, as we will discuss further in relation to the comment that follows. However, we agree with the reviewer that in the title, the indicator of SES used should be made clear and hence the title of the manuscript has now been changed to: Mediators of the association between parental education and breakfast consumption among adolescents: the ESSENS study Abstract: - Background focusses on SES but then the methods use parental education, this is confusing Education was indeed the only indicator of socioeconomic position used in the present study. Different indicators of socioeconomic position might influence health behaviors and outcomes through different pathways. However, it has been found that education is one of the socioeconomic indicators especially likely to capture aspects of lifestyle and behavior. It is also the indicator most commonly found to be associated with health behaviors and determinants of health behaviors among youth. Measurement of education is also generally reliable, and in the present study was reported by parents themselves. Education is related to income in Norway although, in addition to the length of education, the association is dependent on the type of education. Education also often determines one s occupation. We thus believe that it is appropriate to focus on breakfast consumption and SES in general in the background section of the abstract. Several of the studies referenced in the background also used parental education as an indicator of SEP.

3 - Give values in results This has now been done (lines 14-23). - Conclusion that home environment is 'critical' not demonstrated in results, consider rewording to better reflect results All the factors found to be associated with breakfast consumption are home environmental/parental factors. However, the term home environment is broad and includes several components. We have therefore deleted that sentence from the conclusion which we have now limited to concrete results obtained in the study. Intro: - Explain what is meant by high prevalence in Norway (ln30) and compare this to other countries (some examples in adolescent studies are the HELENA study Public Health Nutr 2013, Law et al Mal JNutr 2013, O'Sullivan et al Public Hlth Nutr 2009, Jääskeläinenet al Nutr Metabol CVD 2013). This has now been added as follows in the manuscript (lines 34-37): A high prevalence of breakfast skipping has been documented among adolescents in Norway, with only 63% of adolescents consuming breakfast daily (1). The same was true for other countries included in the same study, with rates of daily breakfast consumption ranging from 40% in Slovenia to 74 % in the Netherlands (1). - Be clear about exactly where the gap is in the current literature and how this study will address it - I think its in there but it just needs to be made clearer We have now elaborated on the gap in the literature that this paper attempts to address as follows (lines 52-53, lines 64-66): The present study will help address this gap by looking at multiple correlates of breakfast consumption among adolescents.

4 More studies exploring mediators of socioeconomic differences in breakfast consumption using a broader range of mediators are therefore needed to address this gap in the literature. Such studies will help design effective interventions targeting socioeconomic differences in breakfast consumption. Methods: -Give age range of adolescents usually in the 8th grade (this may differ to other countries) This has now been added (line 78). -Provide ethics approval details As per the journal s request, the ethical considerations section is provided at the end of the manuscript (lines ), as follows: Ethical clearance for the study was obtained from the Norwegian Social Science Data Service. Written informed consent was obtained from all parents of participating adolescents; adolescents provided assent. School administrators also provided consent for the study. -More information is required on the questionnaire. Is there a reference that could be added here? Needs detail on type of info collected, the program used, whether questions were compulsory etc. A completion time of mins is quite long for an adolescent survey. What reliability testing was done? What changes were made following pre-testing? Only few adolescents took over 40 mins to complete the survey, and most completed the survey within 30 minutes. Reliability testing was not done in this particular sample, but questions with evidence of reliability and/or validity in samples of the same age (with samples including Norwegian adolescents) were used. Clarity and length were assessed through the pre-test study. Additional information was added to address the other concerns as follows (lines 84-92):

5 A web-based questionnaire was used to collect data from the adolescents, using the LimeSurvey data collection tool. The questionnaires were filled in at school, and took approximately minutes to complete. Research group members were present during data collection to assist participants. The questionnaire contained questions about dietary behaviors, physical activity and selected sedentary behaviors, as well as selected correlates of these behaviors. Only five of the questions were mandatory. The questionnaire was pre-tested for clarity and length among a group of adolescents (n=23) of the same age as the study participants, prior to the main study. The questionnaire was subsequently shortened and some questions were rephrased. - ln 87- validated for what and what were the results? There can be varying 'levels' of validation. This has now been clarified (lines ). - how were breakfast foods defined? The following examples were provided for breakfast foods: bread, cereals, milk. This has now been added to the manuscript (line 116). - Justify why only the highest educated parent was used in the analysis. Why not investigate the parent who was predominately at home or responsible for the shopping/cooking? How were split families dealt with where children spend some time at one parent's residence and the rest at the others residence? What about children looked after by grandparents? The highest level of parental education has been used as an indicator of SEP in several studies where clear socioeconomic gradients were shown, indicating the usefulness of this categorization in research on socioeconomic inequalities in health. In particular in a Norwegian context where both mothers and fathers are often employed and where shopping is usually conducted by both parents, focusing on one parent would not give a good reflection of family SEP. This classification was used for all children. The definition of parent was broad in order to correctly classify all adolescents; the options provided were: mother, father, stepmother, stepfather, female guardian, male guardian; these options were provided under headings parent 1 and parent 2. The latter categories were included to cover those living with grandparents among others. This measure of parental education and categorization has been used in several other studies (e.g. ref. 1-3). The section has been edited as follows adding some details about the measure (lines ):

6 Two questions assessing parental education were included on the parental informed consent form for the adolescent. The questions assessed the education of guardian 1 and guardian 2 (could be mother, father, stepmother, stepfather, male guardian, female guardian). Parental education was categorized into: low (12 years of education or less, which corresponded to secondary education or lower) and high (13 years of education and more, which corresponded to university or college attendance). Educational status of the parent with the longest education or else the one available was used in the analyses. -for stats analysis, refer to your Figure 1 This has now been added (line 167). - add full details for SPSS program (check how to reference it) This has now been added as follows (lines ): All analyses were conducted using IBM SPSS Statistics, version 22.0 (IBM Corp., Somers, New York, USA). - explain why you categorised the breakfast consumption rather than using it as a continuous variable (fine to do, just need to justify it) Breakfast consumption was categorized because the continuous variable was highly skewed and because the recommendation when it comes to breakfast intake is not to skip breakfast, therefore allowing us to compare those who meet recommendations vs. those who do not. This has now been added to the manuscript (lines ). Results: - We often see important differences between boys and girls in dietary studies. Could you please include results split by gender? Indeed, some dietary behaviors differ significantly by gender. However, the difference by gender in breakfast consumption in the present study was only borderline significant. We also have no theoretical or empirical evidence suggesting that the mediation results will significantly differ by gender. In addition, not dividing the sample allowed us to improve the power in our study, which is particularly important for the mediation analyses. However, we have added descriptive analyses split by gender in Table 1, page 23.

7 - Provide more information in tables around how characteristics of breakfast skippers compared to those who ate breakfast Table 1 has now been edited and the requested information has been added (page 23). - You adjusted for age - was there much variation in age? There wasn t much variation in age. However, since it is recommended to adjust for age and sex in such studies, we decided to adjust for it. - not clear why some results were adjusted for age and gender and some were not (ln 156) Age and gender were adjusted for in all models, as was stated in the statistical analysis section. We have removed the stated section about adjustment (line 189) so that it does not give a wrong impression that adjustment was done in this case only. Discussion: - Could the association you observe with parental education be due to income? Can you add this in to the analysis? We did not include a measure of income in our study. We have reflected on this issue in the strengths and weaknesses section as follows: Parental education and other indicators of SEP such as income and occupation are correlated. However, existing research suggests that the association between these indicators of SEP and dietary behaviours among children can be specific/independent (37). Therefore, including measures of income and occupation in future studies might allow for the exploration of the independent effects of these indicators on breakfast consumption. - A 'positive' association means that as one variable goes up the other goes up. Do you mean inverse rather than positive when you refer to screen time and breakfast consumption? (ln 217,220)

8 Thank you for noting this. It was indeed a mistake, and has now been rectified (lines 249, 253) - Refers to evidence of reliability and validity of measures - make sure sufficient detail goes in the methods about this (give actual values) We have now added more details regarding the validity and reliability of the measures including actual values, as follows (lines , , lines ): This question has shown evidence of moderate test-retest reliability (% agreement of 83% and 81% respectively for weekday and weekend measures) and moderate construct validity (% agreement of 80% and 87% respectively for weekday and weekend measures) among year old European children (26). The questions were adopted from a previously validated questionnaire among European 11 year-olds (26). For the question assessing parental co-participation, ICC for test-retest reliability was 0.74 and ICC for construct validity was The respective ICC values for the question assessing parental modelling were 0.71 and For the question assessing parental rules, percentage agreement values for test-retest reliability and construct validity were 79% and 67% respectively. For the question assessing the availability of breakfast food, percentage agreement values for test-retest reliability and construct validity were 75% and 80% respectively (26). The screen time measures were adopted and modified (to reflect recent patterns in screen-based activities) from previous measures with evidence of moderate construct validity (26) and moderate test-retest reliability (26, 27). - Needs to finish with an appropriate conclusion A conclusion section has now been added as follows (lines ): The rate of breakfast skipping found in this study was high and was more pronounced among those with low parental education. Increasing the availability of breakfast food, improving

9 parental modeling of breakfast consumption and targeting screen time might be promising strategies to reduce parental educational differences in breakfast consumption. Check for spelling and grammar throughout - e.g. ln 62, 144,259 This has now been done and the necessary changes have been made. Tables and Figures usually have the first letter in capitals in text - check journal formatting rules This is correct and we have made the necessary changes in the manuscript. Reviewer 2: Overall: This study examines the mediators that explain the relationship between parent education and breakfast skipping in a school-based sample of Norwegian adolescents. This paper should be of interest to the readers but more details on the methods are needed. Authors should also consult with a statistician to review their approach to mediation analysis, which differs from that of other papers presenting mediation analyses. Further justification of the validity of questionnaire items is needed. The concerns of the reviewer have been addressed below. Abstract (and methods): Include the year and months when data were collected This has now been added (line 8, lines 81-82). Methods: State the institution that approved the Human Subjects protocol. Was youth assent also obtained? (line 128) As per the journal s request, ethical clearance details are provided at the end of the manuscript, and the section reads as follows:

10 Ethical clearance for the study was obtained from the Norwegian Social Science Data Service. Written informed consent was obtained from all parents of participating adolescents; adolescents provided assent. School administrators also provided consent for the study. Provide a citation for the analytical approach to the mediation analysis. (lines 88, 99) A citation for the analytical approach to the mediation analysis has already been provided (Line 166), this citation has also been added on line 156. This reference explains the mediation method and also provides the SPSS macro used. The citations for the validity and reliability of the questionnaire are not sufficient for at least some of the measures in this study (parent rules, modeling, co-participation, and breakfast availability). Justify further their use, provide additional citations that are relevant to this paper, or elaborate on the limitation of using measures that have not been adequately validated. Were the specific questions used in this study cognitively tested in a similar population? Yes, the measures were tested for test-retest reliability and construct validity among European adolescents (including Norwegian adolescents). This has now been elaborated as follows in the manuscript (lines , , lines ): This question has shown evidence of moderate test-retest reliability (% agreement of 83% and 81% respectively for weekday and weekend measures) and moderate construct validity (% agreement of 80% and 87% respectively for weekday and weekend measures) among year old European children (26). The questions were adopted from a previously validated questionnaire among European 11 year-olds (26). For the question assessing parental co-participation, ICC for test-retest reliability was 0.74 and ICC for construct validity was The respective ICC values for the question assessing parental modelling were 0.71 and For the question assessing parental rules, percentage agreement values for test-retest reliability and construct validity were 79% and 67% respectively. For the question assessing the availability of breakfast food, percentage agreement values for test-retest reliability and construct validity were 75% and 80% respectively (26).

11 The screen time measures were adopted and modified (to reflect recent patterns in screen-based activities) from previous measures with evidence of moderate construct validity (26) and moderate test-retest reliability (26, 27). Did the authors mean that parent education data were collected at the same time as the consent forms (wording is unclear)? The sentence has now been rephrased as follows (lines ): The question assessing parental education was included on the parental informed consent form for the adolescent. Results: How do those with missing data differ from those with complete data? There was no statistically significant difference between those with missing data and those with missing data in terms of gender, breakfast consumption and correlates of breakfast consumption. This has now been added to the manuscript (lines ). Table 1 & 2: These should be to stand alone add details or footnotes to explain the response options for the variables for parent modeling, availability, rules; In Table 2, headers of columns need more explanation or definition in the footnotes. Also, the footnotes state that all paths are adjusted for ethnicity and gender but text (lines 131 and 136) also states that some analyses were adjusted for parent education. These changes have now been made (Table 1, page 23 and Table 2, page 24). I do not think that intermediate steps should be adjusted for the predictor. According to citations below, steps in mediation analysis include: 1) the predictor (parent education) is associated with the outcome (breakfast frequency); 2) the predictor is associated with the mediators; and 3) the mediators are associated with the outcome. In step four of the mediation analyses, the mediator variable, which is significantly related to both predictor and outcome variables, is included in the regression analysis. Mediation (partial or full) is assumed if the association between the predictor

12 and the outcome variable is reduced significantly by the inclusion of the mediator in the regression model. Double-check with a statistician to see if adjustment for parental education is appropriate. If the analysis is done as described above, the authors can also present the percentage of the variation in the predictor-outcome relationship that is explained by the mediators. Lockwood CM, De Franceso MC, Elliot DL, Beresford SA, Toobert DJ. Mediation analyses: Applications in Nutrition Research and Reading the literature. J Am Diet Assoc 2010; 110: Baron RM, Kenny DA. The moderator-mediator variable distinction in social psychological research: conceptual, strategic, and statistical considerations. J Pers Soc Psychol 1986; 51: Adjustment for the independent variable X (in our case parental education), is done when looking at the b-path in mediation analysis, and this is supported by different authors, for e.g. MacKinnon DP, Fairchild AJ, Fritz MS. Mediation analysis. Annu Rev Psychol. 2007; 58: a representing the relation of X to M, b representing the relation of M to Y adjusted for X, and c the relation of X to Y adjusted for M. Preacher KJ, Hayes AF. Asymptotic and resampling strategies for assessing and comparing indirect effects in multiple mediator models. Behav Res Methods. 2008; 40: Path a represents the effect of X on the proposed mediator, whereas path b is the effect of M on Y partialling out the effect of X. David Kenney further states (

13 It is not sufficient just to correlate the mediator with the outcome because the mediator and the outcome may be correlated because they are both caused by the causal variable X. Thus, the causal variable must be controlled in establishing the effect of the mediator on the outcome. Adjustment for X has been done in several mediation studies that have used the same method used in the present study, for example: Totland TH, Lien N, Bergh IH, Bjelland M, Gebremariam MK, Klepp KI, Andersen LF. The relationship between parental education and adolescents' soft drink intake from the age of years, and possible mediating effects of availability and accessibility. Br J Nutr. 2013;110: Kvaavik E, Totland TH, Bastani N, Kjøllesdal MK, Tell GS, Andersen LF. Do smoking and fruit and vegetable intake mediate the association between socio-economic status and plasma carotenoids? Eur J Public Health. 2014; 24:685-90). Since the dependent variable in this study is dichotomous and the mediators are continuous and hence measured on different scales, it is not possible to compute mediated proportions, which we confirmed by contacting statisticians with particular expertise in mediation analysis. Discussion: Line 198. What are possible explanations for the decline in breakfast consumption in Norway? How do these findings concur with those explanations? To our knowledge, no study has looked into the reasons for the decline in breakfast consumption in Norway over the past decade. Our cross-sectional data does not provide much evidence to explain the decline. However, it could be hypothesized that an increase in screen time following changes in the development of screens and screen-based activities could play a role. This has now been added in lines : There have been significant changes in the availability of different screens over the past decade. This can result in an increase in screen time, which might at least to some degree explain the documented small decrease in breakfast consumption over the past decade (1).

14 References 1. Totland TH, Bjelland M, Lien N, Bergh IH, Gebremariam MK, Grydeland M, Ommundsen Y, Andersen LF. Adolescents' prospective screen time by gender and parental education, the mediation of parental influences. Int J Behav Nutr Phys Act. 2013;10: Grydeland M, Bjelland M, Anderssen SA, Klepp KI, Bergh IH, Andersen LF, Ommundsen Y, Lien N. Effects of a 20-month cluster randomised controlled schoolbased intervention trial on BMI of school-aged boys and girls: the HEIA study. Br J Sports Med. 2014; 48: Vik FN, Te Velde SJ, Van Lippevelde W, Manios Y, Kovacs E, Jan N, Moreno LA, Bringolf-Isler B, Brug J, Bere E. Regular family breakfast was associated with children's overweight and parental education: Results from the ENERGY cross-sectional study. Prev Med. 2016; 91: