Evaluation of planned number of children, the well-being of the couple, and associated factors in a prospective cohort in Yokohama (HAMA study): study protocol

doi:10.21203/rs.3.rs-2863209/v1

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Study protocol

Evaluation of planned number of children, the well-being of the couple, and associated factors in a prospective cohort in Yokohama (HAMA study): study protocol

https://doi.org/10.21203/rs.3.rs-2863209/v1

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Background

Many developed countries including Japan are experiencing declining birth rates, particularly in urban areas. There is a gap between the planned number of children and the actual number of children, which has been attributed to various factors. The following issues that are considered indispensable for addressing the problem of declining birth rates have been rarely investigated: childcare leave and employment policies, childcare services, financial support, husbands’ contributions to household chores and childcare, marriage support, and the community. In addition, the relationship between these situations and their well-being is also important and is one of the main outcomes. Therefore, we propose the present HAMA study for having a baby, parenting, and marriage life (HAMA = 'H'aving 'A' baby, parenting, and 'MA'rriage life) in Yokohama (an urban area) to examine the aforementioned issues.

Methods

In this large-scale cohort study, we plan to elucidate the actual situation of families and child rearing in Yokohama, evaluate the current policies, and propose future measures to prevent a decline in birth rate. Overall, 10,000 young married couples (wives aged 20–39 years as of 2022) will be randomly selected, and a survey form will be sent to them annually. They will be followed up for 5 years to examine the factors associated with the planned number of children, well-being of the couple, childcare support policies, externalization of housework and childcare, fathers’ participation in housework and childcare, wives’ free time, loneliness and social connectedness, relationship with the spouse, and if they are working, questions regarding their work style and work-life balance will also be included. Ultimately, a conceptual model of the planned number of children and associated factors will be developed.

Discussion

This study will help identify issues related to families and childcare in the urban areas of Japan with high population concentrations. The separate collection of data from husbands and wives will help identify their connectedness or disconnectedness. In addition, this study will build a conceptual model for the planned number of children and well-being after considering various factors that reflect contemporary realities and urban characteristics.

planned number of children

well-being

HAMA study

birth rate decline

housework

childcare

Many developed countries, including Japan, are experiencing declining birth rates, particularly in urban areas. As of 2020, total fertility rate was 1.33 in Japan, 1.64 in the United States, 1.58 in the United Kingdom, 1.53 in Germany, 1.82 in France, and 1.66 in Sweden [1]. Birth rate is declining at an accelerating pace in the urban areas of Japan, with the total fertility rate tending to be low at 1.12 and 1.26 in Tokyo and Kanagawa Prefectures (including Yokohama City), respectively. The Japanese population, which was 120 million in 2000, is expected to decline to 101.9 million by 2050 and to 59.7 million by 2100 [2]. Several socioeconomic factors contribute to delays in child-bearing. The lack of facilities such as affordable housing, flexible and part-time career options for women, and affordable childcare have contributed to low fertility and birth rates. Couples delay starting a family, which causes a decline in their fertility levels because of ovarian aging and associated reasons, leading to a reduced chance of conception [3].

The declining birth rate will reduce population size not at all ages but only among the young. Low fertility produces an age structure that creates momentum for future population decline, which must be stopped for the population to remain demographically sustainable. A gap has been reported between the number of desired children and the actual number of children. In a survey conducted in Japan in 2015, the ideal number of children was 2.32 and the planned number was 2.01 [4], which has been attributed to various factors such as financial support for the child, the age of childbearing because of later marriages, infertility, and the psychological and physical burden of childcare. In Japan, the Basic Law on Measures for Society with a Decreasing Birthrate was implemented in 2003 [5], in which support for childcare and work-life balance was promoted to combat the declining birthrate. However, the total fertility rate remains low and further support for childrearing is necessary. In April 2023, a new Children and Families Agency was established to consolidate and implement policies for children’s welfare [6].

Cohort studies focusing on fertility decline are currently being conducted globally. The Panel Study of Income Dynamics, being conducted in the United States since 1968, tracks household and individual income, education, and labor market participation [7, 8]. In the United Kingdom, the British Birth Cohort Studies are being conducted, including four cohort studies on people born in 1946, 1958, 1970, and 2000 [9]. In Germany, the German Family Panel Survey is being conducted annually since 2010, surveying more than 10,000 families to determine their family life, financial situation, and health status [10]. A cohort study on declining fertility is being conducted in Japan. The Japan General Social Survey is being conducted since 2000 and includes various items related to life planning, family relationships, and social support [11, 12].

The following issues are considered indispensable for addressing the problem of declining birth rates: childcare leave and employment policies, childcare services, financial support, husbands’ contributions to household chores and childcare, marriage support, and the community. Four main factors have been suggested to affect fertility rates. The first is work compatibility, which is discussed in terms of the relationship between the childcare leave system, shorter working hours, female employment rate, and fertility rate [13, 14]. Yamaguchi (2019) investigated the impact of parental leave policies on women's career and fertility choices and revealed both positive and negative effects [15]. Second, childcare services should be enhanced [16–18]. Hwang et al. (2015) [19] suggest that enhanced childcare services can achieve two seemingly contradictory goals: increasing women's labor force participation and increasing fertility. Third, economic support for the child-rearing generation is a measure to combat the declining birth rate [20, 21]. A study by Riphahn and Wiynck (2017) [22] revealed that child allowance and tax reform in Germany showed a positive effect on fertility when high-income and low-income couples decided to have a second child. Fourth, a relationship between men's participation in housework and childcare and the declining birth rate has been suggested [23]. McDonald (2000) suggested that men's participation in housework and childcare may lead women to have more children [24]. Declining fertility rate is a complex problem involving many factors. In addition, issues related to the declining birth rate unique to urban areas have been noted [25, 26].

To the best of our knowledge, only a few studies have comprehensively examined the aforementioned factors and studies focusing on urban areas are limited. Therefore, considering the differences in urban and rural regions, we propose the present HAMA study for having a baby, parenting, and marriage life (HAMA = 'H'aving 'A' baby, parenting, and 'MA'rriage life) in Yokohama (an urban area) to examine the aforementioned factors. In this large-scale cohort study, we plan to elucidate the actual situation of families and parenting in Yokohama, evaluate policies, and suggest future measures to prevent a decline in birth rate.

Study design

This prospective cohort study will be conducted at a single center, where a questionnaire survey will be carried out among married couples residing in Yokohama City. Ten thousand young married couples (wives born between April 2, 1983 and April 1, 2001, who have attained the age of 20–39 years in 2022) will be randomly selected, and a survey form will be sent to them by post. Two survey forms with the same survey items will be sent: one for the wives and one for the husbands, and each individual will be required to answer the survey form and submit it. The survey will have questions regarding satisfaction with life, health conditions, thoughts about children and the number of children, utilization of time in routine, automation of housework, support for parenting, social connections, and personal items. A return envelope will be enclosed with the form, and participants will have the option of sending their responses either by posting in the return envelope or by filling the online form. These forms will be sent annually between December and February for 5 years. Each form will be assigned a household ID and identifier for men and women, allowing for easy follow-up. Major survey items, such as the well-being of the couple and the planned number of children, will continue to be included in the survey form to identify changes over time during the study period.

Inclusion criteria

Irrespective of whether the couple has children at the start of the survey, the inclusion criteria will be as follows:

Married couples residing in Yokohama city as of December 2022

Wives aged between 20 and 39 years

Families with children under 6 years old (preschoolers) or families without children

Exclusion criterion

Couples who do not disclose their residential address will be excluded from the study.

Collection and assessment of data

Based on these criteria, 10,000 households will be randomly selected from the resident registration system of Yokohama City, which is maintained by the government, and the data are made available for research of public interest. The first survey was sent to participants in January 2023 and responses were collected. To improve the collection rate, reminder postcards will be sent to participants: the first reminder postcard, about 3 weeks after sending the survey forms, and the second reminder postcard, about 5 weeks after sending the survey forms.

A written explanation of the survey was provided with the first survey form. A check box will be provided on the survey form to confirm consent to the survey, and the checked box will be considered written informed consent. The completed survey forms with consent will be used for data analysis.

The questionnaire will include questions with reliability and validity from previous studies [27–32] and newly created questions. The questions regarding the planned number of children will be the same as those used in the Japanese government statistics. The well-being of the couple will be measured using a subjective analysis and the Gallup Index [33]. During the evaluation of childcare support policies, we will ascertain the awareness and use of current policies. The externalization of housework and childcare will identify the external services used and the frequency of their use. Fathers’ participation in housework and childcare and wives’ free time will be used to measure husband and wives' time and satisfaction with housework and childcare. Regarding loneliness and social connectedness, the social connectedness index developed in K6 [27] and in previous studies [29–31] will be used.

The questionnaire will also include items regarding household chores, such as the time spent on housework, childcare, sleep, the use of automation for housework (e.g., dishwashers and robot vacuum cleaners) and household chores (e.g., housekeeping and shopping services). Additionally, it will include questions for analyzing relationships with the spouse and, if they are working, questions regarding their work style and work-life balance will also be included.

From a medical point of view, the questionnaire will include questions regarding children delivery methods, parents’ interest in painless delivery, and satisfaction with access to perinatal and pediatric care and the healthcare delivery system. The health statuses of the children and parents will also be included in the questionnaire. The assessment plan that will be used for the analysis is presented in Fig. 1.

It has been indicated in the questionnaire and instruction document that responses to the survey questions are voluntary and that no one will be disadvantaged by not responding. The instruction document also clearly indicates that questions that the respondents do not want to answer should be omitted. Opportunities to withdraw consent to participate in the survey are also provided.

Primary endpoints

The primary outcomes of this study will be the planned number of children and couples’ well-being.

Secondary endpoints

The secondary endpoints of this study will be the evaluation of childcare support policies and wives’ free time. Additionally, the survey will determine the status of the externalization of housework and childcare, husbands’ participation in housework and childcare, and their sense of loneliness and social connectedness.

Data management

The collected data will be stored securely. The corresponding author will be responsible for data management and survey during the 5-year period. Other team members will have access to the raw data that do not contain personal information.

Patient and public involvement

Our study team includes researchers, pediatricians, obstetricians, gynecologists, public health nurses, and other members who are well-versed in the field. We consulted the Children and Youth Bureau of Yokohama City regarding the study design and questionnaire. They have been in contact with the child-rearing generation and are familiar with their challenges and problems. Their opinions will be reflected in this study. The main research method of the HAMA study is a questionnaire survey; however, we recognize the importance of further in-depth research through detailed interviews and group interviews with the parties involved. It is also necessary to administer this survey to couples in their 40s, who cannot be included in the study. Therefore, we plan to conduct further interviews with these individuals.

Sources of bias

One important bias is the consent bias. As this study will be conducted following ethical guidelines, we will exclude the data of individuals who do not provide consent. Additionally, response bias, which refers to several factors that can lead someone to respond falsely or inaccurately to a question, may occur. To avoid such biases, it is necessary to increase the response rate as much as possible. Therefore, we have chosen a sample size of 10,000 couples and prepared a dedicated website to disseminate information and gain trust.

Maintaining confidentiality

The collected data will be stored securely. The completed questionnaires will be kept in the study office at Yokohama City University. The collected survey data will not contain any identifiable personal information. Only a few members will have access to the survey form data. The data will be anonymized by excluding and encoding personal information. The processed data will be shared only with the research team, and the data linkage software will be adequately protected to maintain security and privacy.

Statistical analyses

Stratified analyses of income, education, and residential area will be performed. Cross-sectional and longitudinal analyses will be performed on the data obtained in this study. We will analyze the correlations between each factor and perform a multiple or logistic regression analysis with the planned number of children and couple's well-being as objective variables. In addition, a structural equation modeling will be used to examine the relationship between each factor. A longitudinal analysis will be used to analyze the relationship between changes in the planned number of children, the well-being of the couple, and other factors. All analyses will be performed using the R software (R Foundation for Statistical Computing, Vienna, Austria), Stata (StataCorp LLC, College Station, TX, USA), or SPSS (SPSS Inc., Chicago, IL, USA).

Dissemination of data

The results of this survey will be presented at academic conferences and published as research papers in relevant journals. Furthermore, the results will be reported to the administration of Yokohama City and other administrative agencies.

Ethics approval

This study has been approved by the Ethics Committee of Yokohama City University (reference number: 2022-10, dated December 15, 2022) and will be conducted following the appropriate ethical guidelines. The data collected in this study, excluding personal information, will be shared only with the study team members. The study team members will regularly attend ethics training sessions. Opportunities to withdraw consent to participate in the survey are provided to participants.

This study will address an important issue pertaining to the declining birth rate in Japan’s urban areas. To the best of our knowledge, this will be the first study to elucidate the effect of various factors, such as childcare support policies, the status of outsourcing housework and childcare, and husbands’ participation in household chores and childcare, on the planned number of children and the well-being of couples in Yokohama City.

Becker (1960) [34] proposed the following model for the optimal number of children:

$${n}^{*}=\frac{Y+w(T+h+k)}{2(e+w*t)}$$

where n* is the optimal number of children, Y is the husband's income, w is the wife's wage rate, T is the available time without the wife's childcare assistance, and h is the childcare support time of grandparents or husbands. This suggests that the determinants of the number of children are (1) income, (2) wife's free time, and (3) educational and childcare expenses and time, in addition to other factors (age at marriage, especially that of the wife). This model is a leading economic model for fertility and has been used in many recent studies [35–39].

However, Becher's model is more than 60 years old, and has undergone significant changes regarding way of life and values. Kögel (2004) [40] challenged the validity of the Becker model in explaining the relationship between fertility and female employment, suggesting that the association did not change over time in Organisation for Economic Co-operation and Development countries, contrary to what the model predicts. In addition, the model does not include factors relating to the husband, the wife's employment status, the couple's values and ideas, and the well-being, loneliness, and social ties of the couple. The present study will consider this model; however, we will construct a modified model that will reflect contemporary realities and urban characteristics.

After delivery, many women experience health issues that may necessitate vacation from work. The likelihood of returning to work after maternity leave may be increased through structural interactions between supervisors and workers on maternity leave, supported by early medical advice from occupational physicians. To address this issue, the Mom@Work study has been proposed [41], where pregnant women who work at least 12 h weekly for one of the 15 participating businesses will be enrolled. The managers of these expectant women will be randomly assigned to the intervention or control group, where those in the intervention group will be in touch with their employees during maternity leave and offer early support of the occupational physician. In the control group, the managers will not be structurally connected to their staff members during maternity leave. The Mom@Work study will provide important information regarding employees’ return to work after delivery. Additionally, the role of supervisors and occupational physicians in the successful return to work after childbirth will be clarified.

Another study [42] has proposed two possible solutions from an occupational health perspective. First, companies should establish support systems to assist working women during pregnancy and childbirth. Such systems would require the cooperation and understanding of coworkers, including men, and the introduction of flexible work schedules designed to allow workers to care for family members with disabilities. Second, companies should guarantee workers the right to take sick leave and return to work, so that they can balance work with the need to treat chronic conditions.

Our study will help identify issues related to families and childcare in the urban areas of Japan with high population concentrations. The separate collection of data from husbands and wives will help identify their connectedness or disconnectedness. This study will build a conceptual model for the planned number of children after considering various factors that reflect contemporary realities and urban characteristics. Well-being will be used as an objective variable to identify associations with various factors such as parenting and marital relationships.

Our study has a limitation in that only self-reported data will be analyzed, which may cause a high risk of bias.

In conclusion, the data generated from this study will contribute to policy planning and evaluation globally and in Japan through evidence-based policymaking for childcare support policies and measures to prevent declining birthrates.

HAMA ‘H’aving ‘A’ baby, parenting, and ‘MA’rriage life

Ethics approval and consent to participate

This study has been approved by the Ethics Committee of Yokohama City University (reference number: 2022-10, dated December 15, 2022) and all the methods will be conducted according to the relevant guidelines and regulation. The data collected in this study, excluding personal information, will be shared only with the study team members. The study team members will regularly attend ethics training sessions. Opportunities to withdraw consent to participate in the survey are provided to participants. Informed consent will be obtained from all the participants.

Consent for publication

Not applicable

Availability of data and materials

Not applicable

Competing interests

The authors declare that they have no competing interests.

Funding

This study is partially supported by a grant from the 2022–2023 Research Development Fund of Yokohama City University and fundraising activities for the YCU Vision 100 project of Yokohama City University.

Authors’ contributions

KH contributed to the study conception and design, data collection, data management, and drafting of the manuscript; KM contributed to the study conception, design, and coordination with stakeholders; and SS, MS, IS, KK, AA, and MY contributed to the development of questionnaire items and provided expert advice on the research. All authors have read and approved the final manuscript.

Acknowledgements

The authors are grateful to the citizens of Yokohama City for their cooperation in this study. We also thank the Children and Youth Bureau of Yokohama City. Editorial support in the form of medical writing, assembling tables and creating high-resolution images based on authors’ detailed directions, collating author comments, copyediting, fact checking, and referencing, was provided by Editage, Cactus Communications.

Organisation for Economic Co-operation and Development. Fertility rates. In: OECD family database. Organisation for Economic Co-operation and Development. 2022. https://www.oecd.org/els/family/SF_2_1_Fertility_rates.pdf. Accessed 3 March 2023.
Ministry of Land, Infrastructure, Transport and Tourism, Government of Japan. Final summary of "long-term perspectives on national land". In: Reference materials. Ministry of Land, Infrastructure, Transport and Tourism, Government of Japan. 2021. https://www.mlit.go.jp/policy/shingikai/content/001412278.pdf. Accessed 3 March 2023.
Nargund G. Declining birth rate in developed countries: A radical policy re-think is required. Facts Views Vis Obgyn. 2009;1:191-3.
Cabinet Office, Government of Japan. Annual report on the declining birthrate. Cabinet Office, Government of Japan. 2022. https://www8.cao.go.jp/shoushi/shoushika/whitepaper/measures/w-2022/r04pdfhonpen/pdf/s1-5.pdf. Accessed 3 March 2023.
Cabinet Office, Government of Japan. Efforts to deal with the declining birthrate. Cabinet Office, Government of Japan. 2015. https://www8.cao.go.jp/shoushi/shoushika/whitepaper/measures/english/w-2015/pdf/part1_2-1.pdf. Accessed 3 March 2023.
The Japan Times. Japan enacts law to launch new agency to tackle children's issues. The Japan Times. 2022. https://www.japantimes.co.jp/news/2022/06/15/national/children-agency-legislation/. Accessed 3 March 2023.
Hofferth SL. Race/ethnic differences in father involvement in two-parent families: culture, context, or economy? J Fam Issues. 2003;24:185-216.
Yeung WJ, Linver MR, Brooks-Gunn J. How money matters for young children's development: parental investment and family processes. Child Dev. 2002;73:1861-79.
Harkness S, Gregg P, Fernández‐Salgado M. The rise in single‐mother families and children’s cognitive development: evidence from three British birth cohorts. Child Dev. 2020;91:1762-85.
Tanskanen AO, Danielsbacka M. Does parental investment shape adult children’s fertility intentions? Findings from a German family panel. Front Sociol. 2021;6:693119.
Kondo K. Does agglomeration discourage fertility? Evidence from the Japanese general social survey 2000–2010. J Econ Geogr. 2019;19:677-704.
Yamamura E. Effects of siblings and birth order on income redistribution preferences: evidence based on Japanese General Social Survey. Soc Indic Res. 2015;121:589-606.
Organisation for Economic Co-operation and Development. Doing better for families. 2011. Available at: oecd.org/social/soc/doingbetterforfamilies.htm.
Neyer GR, Andersson G. Consequences of family policies on childbearing behavior: effects or artifacts? Popul Dev Rev. 2008;34:699-724.
Yamaguchi S. Effects of parental leave policies on female career and fertility choices. Quant Econ. 2019;10:1195-232.
Lee GHY, Lee SP. Childcare availability, fertility and female labor force participation in Japan. J Jpn Int Econ. 2014;32:71-85.
Rindfuss RR, Guilkey DK, Morgan SP, Kravdal Ø. Child-care availability and fertility in Norway. Popul Dev Rev. 2010;36:725-48.
Bergsvik J, Fauske A, Hart RK. Can policies stall the fertility fall? A systematic review of the (quasi‐) experimental literature. Popul Dev Rev. 2021;47:913-64.
Hwang J, Park S, Shin D. Two birds with one stone: Female labor supply, fertility, and market childcare. J Econ Dyn Control. 2018;90:171-93.
Laroque G, Salanié B. Identifying the response of fertility to financial incentives. J Appl Econom. 2014;29:314-32.
Brewer M, Ratcliffe A, dSmith S. Does welfare reform affect fertility? Evidence from the UK. J Popul Econ. 2012;25:245-66.
Riphahn RT, Wiynck F. Fertility effects of child benefits. J Popul Econ. 2017;30:1135-84.
Nomaguchi KM, Milkie MA. Costs and rewards of children: the effects of becoming a parent on adults’ lives. J Marriage Fam. 2003;65:356-74.
McDonald P. Gender equity in theories of fertility transition. Popul Dev Rev. 2000;26:427-39.
Wiechmann T, Pallagst KM. Urban shrinkage in Germany and the USA: A comparison of transformation patterns and local strategies. Int J Urban Reg Res. 2012;36:261-80.
Haase A, Rink D, Grossmann K, Bernt M, Mykhnenko V. Conceptualizing urban shrinkage. Environ Plan A. 2014;46:1519-34.
Kessler RC, Andrews G, Colpe LJ, Hiripi E, Mroczek DK, Normand SL, et al. Short screening scales to monitor population prevalences and trends in non-specific psychological distress. Psychol Med. 2002;32:959-76.
Cabinet Office, Government of Japan. Report on the 2020 international attitude survey on low fertility society. Cabinet Office, Government of Japan. 2021. https://www8.cao.go.jp/shoushi/shoushika/research/r02/kokusai/pdf_index.html. Accessed 3 March 2023.
Russell DW. UCLA Loneliness Scale (Version 3): Reliability, validity, and factor structure. J Pers Assess. 3^rd version. 1996;66:20-40.
Arimoto A, Tadaka E. Reliability and validity of Japanese versions of the UCLA loneliness scale version 3 for use among mothers with infants and toddlers: a cross-sectional study. BMC Womens Health. 2019;19:105.
Arimoto A, Tadaka E. Individual, family, and community factors related to loneliness in mothers raising children less than 3 years of age: a cross-sectional study. BMC Womens Health. 2021;21:226.
Shafer EF. Wives’ relative wages, husbands’ paid work hours, and wives’ labor-force exit. J Marriage Fam. 2011;73:250-63.
Sommers BD, Goldman AL, Lee D, Epstein AM. Survey mode effects and insurance coverage estimates in the redesigned Gallup well-being index. Health Serv Res. 2019;54:940-6.
National Bureau of Economic Research. An economic analysis of fertility. In: Demographic and economic change in developed countries. National Bureau of Economic Research; 1960. https://www.nber.org/system/files/chapters/c2387/c2387.pdf. Accessed 15 March 2023.
Doepke M, Kindermann F. Bargaining over babies: theory, evidence, and policy implications. Am Econ Rev. 2019;109:3264-306.
Fernández R. Women's rights and development. National Bureau of Economic Research. 2009. Available at: http://www.nber.org/papers/w15355.
Galor O. The demographic transition: causes and consequences. Cliometrica (Berl). 2012;6:1-28.
Goldin C. The quiet revolution that transformed women's employment, education, and family. Am Econ Rev. 2006;96:1-21.
Greenwood J, Seshadri A. Technological progress and economic transformation. In: Aghion P, Durlauf S, editors. Handbook of Economic Growth. Elsevier; 2005. p. 1225-73.
Kögel T. Did the association between fertility and female employment within OECD countries really change its sign? J Popul Econ. 2004;17:45-65.
Stomp-van den Berg SG, Van Poppel MN, Hendriksen IJ, Bruinvels DJ, Uegaki K, De Bruijne MC, et al. Improving return-to-work after childbirth: design of the Mom@Work study, a randomised controlled trial and cohort study. BMC Public Health. 2007;7:43.
Muto G, Yokoyama K, Endo M. Solutions against declining birthrates confronting Japan's aging society by supporting female workers in harmonizing work with their health and social issues: fertility, chronic illness, and raising children. Nihon Eiseigaku Zasshi. 2018;73:200-9 [Article in Japanese].

No competing interests reported.

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Version 1

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You are reading this latest preprint version

Evaluation of planned number of children, the well-being of the couple, and associated factors in a prospective cohort in Yokohama (HAMA study): study protocol

Status:

Version 1

Abstract

Figures

BACKGROUND

METHODS

Study design

Inclusion criteria

Exclusion criterion

Collection and assessment of data

Primary endpoints

Secondary endpoints

Data management

Patient and public involvement

Sources of bias

Maintaining confidentiality

Statistical analyses

Dissemination of data

Ethics approval

DISCUSSION

Abbreviations

Declarations

References

Additional Declarations

Status:

Version 1