Prevalence of loneliness amongst older people in high-income countries: A systematic review and meta-analysis

Kavita Chawla; Tafadzwa Patience Kunonga; Daniel Stow; Robert Barker; Dawn Craig; Barbara Hanratty

doi:10.1371/journal.pone.0255088

Peer Review History

Original SubmissionApril 30, 2021
7 Jun 2021 Decision Letter - Muhammad Shahzad Aslam, Editor PONE-D-21-14347 Prevalence of Loneliness amongst Older People in High-Income Countries: A Systematic Review and Meta-analysis PLOS ONE Dear, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. Please improve the discussion and elaborate in details of comment as under. Please submit your revised manuscript by 15th June 2021. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file. Please include the following items when submitting your revised manuscript: A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'. A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'. An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'. If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter. If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols. We look forward to receiving your revised manuscript. Kind regards, Muhammad Shahzad Aslam, Ph.D.,M.Phil., Pharm-D Academic Editor PLOS ONE Journal Requirements: When submitting your revision, we need you to address these additional requirements. 1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf 2. Please amend either the abstract on the online submission form (via Edit Submission) or the abstract in the manuscript so that they are identical. 3. Please include a separate caption for each figure in your manuscript. 4. Please include captions for ALL your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly. Please see our Supporting Information guidelines for more information: http://journals.plos.org/plosone/s/supporting-information. [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Yes Reviewer #2: Yes ******** 2. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ****** 3. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: Yes ****** 4. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: Yes ****** 5. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: 1. Introduction: “Tracking loneliness is …… public health problem is limited.” Any added literature support? 2. Search strategy will be confirmed. “Five electronic databases were searched from inception to July 2020”, however, Inclusion criteria mentioned, “published between 2008 and 2020”. The search strategy was not matched. It may readers misunderstanding and difficulty to qualify methodology. 3. Classification of Loneliness: Added references for definition. 4. Definition and criteria for the “High-income countries”. 5. Strengthen and limitation: Readers lack understand of this manuscript's strengths and limitations. Please add more specific paragraphs to the end of this manuscript. Reviewer #2: 1- Please provide data identification method clearly 2-Please provide details discussion by comparison of finding of relevant studies 3-Please rewrite the conclusion. According to author "Even though older age is not synonymous with loneliness, approximately one in four older adults experience loneliness experience loneliness. Even though severe or prolonged loneliness is less common, the burden of loneliness in amongst older adults is an important public health and social problem" The paragraph is unclear and does not correspond to conclusion 4-Please elaborate prisma flow diagram particularly reason of exclusion in data screening stage 5-According to author statement". There was a very high degree of heterogeneity" Please elaborate in discussion why there is high heterogeneity observed? 6-Please provide rationale of meta-analysis results and explain in discussion 7-It is recommended to draw the illustration of Geographical variation in prevalence of loneliness within and between countries mentioned inside the manuscript. 8-please provide rationale on high risk of bias in studies identified. ****** 6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #1: Yes: Yun Jin Kim Reviewer #2: Yes:** Saima Nisar [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0255088.r001
Revision 1
15 Jun 2021 Author Response Reviewers' comments: Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: 1. Introduction: “Tracking loneliness is …… public health problem is limited.” Any added literature support? Our response: Thank you for your suggestion. We have added the following reference to support our narrative: Cacioppo JT, Cacioppo S. The growing problem of loneliness. The Lancet. 2018 Feb 3;391(10119):426. Gerst-Emerson K, Jayawardhana J. Loneliness as a public health issue: the impact of loneliness on health care utilization among older adults. American journal of public health. 2015 May;105(5):1013-9. 2. Search strategy will be confirmed. “Five electronic databases were searched from inception to July 2020”, however, Inclusion criteria mentioned, “published between 2008 and 2020”. The search strategy was not matched. It may readers misunderstanding and difficulty to qualify methodology. Our response: Thank you for your comments. The text has been amended to “Five electronic databases were searched from 2008 to July 2020”. 3. Classification of Loneliness: Added references for definition. Our response: Thank you for your suggestion. We have added a reference to support our statement. Valtorta NK, Kanaan M, Gilbody S, Hanratty B. Loneliness, social isolation and social relationships: what are we measuring? A novel framework for classifying and comparing tools. BMJ Open. 2016;6(4) 4. Definition and criteria for the “High-income countries”. Our response: Thank you. We have included the following statement and reference in support: High income countries were included as defined by the World Bank. World Bank Group. High Income. 2021Available from: https://data.worldbank.org/country/XD 5. Strengthen and limitation: Readers lack understand of this manuscript's strengths and limitations. Please add more specific paragraphs to the end of this manuscript. Our response: Thank you for your suggestion. We have added the following text: Loneliness by definition is a subjective experience. Differences in social structures, ways of life, social norms and expectations are likely to impact on the prevalence of loneliness. Therefore, this review has sought to look at the prevalence of loneliness in countries at a similar stage of economic development over recent years to attempt to produce a more homogenous population group. In using all measures of loneliness, we have pooled people experiencing loneliness over different durations (some over the last week, some over the past year), differing intensities and also differing frequencies. It is yet unclear whether these have similar natural histories. What is known is that both chronic and recent loneliness are associated with increased mortality but it is not clear how the different intensities affect health. Reviewer #2: 1- Please provide data identification method clearly Our response: Thank you. We have reworded the section to include: The selection process consisted of two stages of screening, conducted by two reviewers. Articles were exported from Endnote X9 to Rayyan, an online bibliographic database [26]. The inclusion criteria were tested and refined on sample of titles and abstracts to ensure that they were robust enough to capture relevant articles. One researcher then screened all titles and abstracts of the included articles and another researcher checked 10% of these for accuracy. All articles included for full-text examination were independently checked by both reviewers. Disagreements between the reviewers were resolved either by discussion between the reviewers or with arbitration from another member of the review team. 2-Please provide details discussion by comparison of finding of relevant studies Our response: Thank you for your suggestion. We have added the following text: There is evidence to support the fact that loneliness levels have been static over the past 70 years. A study conducting a comparative analysis of four surveys from the UK between 1945 and 1999, found no change in variations of loneliness between cohorts. Between five and nine percent of people were often lonely, which is similar to the estimated rate of ‘severe’ loneliness with our findings. The range of people feeling at least ‘sometimes lonely’ was more variable. In one of the surveys it was 17 percent and in the other three surveys (including the more recent survey) it was between 27 and 34 percent which is in keeping with this review’s results. 3-Please rewrite the conclusion. According to author "Even though older age is not synonymous with loneliness, approximately one in four older adults experience loneliness experience loneliness. Even though severe or prolonged loneliness is less common, the burden of loneliness in amongst older adults is an important public health and social problem" The paragraph is unclear and does not correspond to conclusion Our response: Thank you for your suggestion, we have reworded our conclusion to: The idea that older age is synonymous with being lonely should be challenged. Whilst one in four older people experience loneliness at some time, severe or prolonged loneliness is uncommon, not universal, and loneliness does not increase with age. Therefore, the burden of loneliness in amongst older adults is an important public health and social problem. 4-Please elaborate prisma flow diagram particularly reason of exclusion in data screening stage Our response: Thank you for your suggestion, we have added the following statement: Reasons for exclusion included: not high income country, having a disease or role-related to those people with a specific health condition (for example heart disease), aged <60 years, baseline not a general population, data not reported, a study reported in more than one paper, published before 2008, and loneliness score were divided into quartile and quintiles and used as cut-offs. 5-According to author statement". There was a very high degree of heterogeneity" Please elaborate in discussion why there is high heterogeneity observed? Our response: Thank you for your comment. We have added the following statement: “…likely due to the differences in the types of measurement tools used, different methods of obtaining data (online, face to face, postal questionnaire), differences in response rates as well as gender..” 6-Please provide rationale of meta-analysis results and explain in discussion Our response: Thank you for your comment, we have changed the statement in our discussion from: Approximately 1 in 4 older adults over 60 experience loneliness at least sometimes. . . TO Our pooled estimate of loneliness prevalence (28.5%, 95%CI: 23.9% to 33.2%) suggests that approximately 1 in 4 older adults over 60 experience some degree of loneliness at least some of the time. Our a-priori subgroup analyses suggest that a smaller proportion of people (around 1 in 12) experience severe loneliness than moderate loneliness (approximately 1 in 4). There was no suggestion that loneliness is more common in people age over 75 than in those age 60-75. 7-It is recommended to draw the illustration of Geographical variation in prevalence of loneliness within and between countries mentioned inside the manuscript. Our response: Thank you for your comment, as this was not initially a focus in our review, there was insufficient data to merit the addition of a figure, however at the end of the paragraph, and we have acknowledged that: Further research to better understand these geographical differences might support learning or understanding from countries with lower prevalence. 8-please provide rationale on high risk of bias in studies identified. Our response: Thank you for your suggestion. We have added the following statement: The potential for bias was identified in 4 out of 9 domains, mainly due to not having enough participants to address the target population. Attachments Attachment Submitted filename: Response to Reviewers.docx https://doi.org/10.1371/journal.pone.0255088.r002
12 Jul 2021 Decision Letter - Muhammad Shahzad Aslam, Editor Prevalence of Loneliness amongst Older People in High-Income Countries: A Systematic Review and Meta-analysis PONE-D-21-14347R1 Dear, We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements. Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication. An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org. If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Muhammad Shahzad Aslam, Ph.D.,M.Phil., Pharm-D Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation. Reviewer #1: All comments have been addressed Reviewer #2: All comments have been addressed ******** 2. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Yes Reviewer #2: Yes ****** 3. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: I Don't Know ****** 4. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: Yes ****** 5. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: (No Response) ****** 6. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: Dear. Author. Many thanks for submitting your revised manuscript to this journal. Overall, the revised manuscript is improved and is relevant to the scope of this journal. Reviewer #2: (No Response) ****** 7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #1: Yes: Dr. Yun Jin Kim, Ph.D Reviewer #2: Yes:** Saima Nisar https://doi.org/10.1371/journal.pone.0255088.r003
Formally Accepted
14 Jul 2021 Acceptance Letter - Muhammad Shahzad Aslam, Editor PONE-D-21-14347R1 Prevalence of Loneliness amongst Older People in High-Income Countries: A Systematic Review and Meta-analysis Dear Dr. Kunonga: I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org. If we can help with anything else, please email us at plosone@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Muhammad Shahzad Aslam Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0255088.r004

Open letter on the publication of peer review reports

PLOS recognizes the benefits of transparency in the peer review process. Therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. Reviewers remain anonymous, unless they choose to reveal their names.

We encourage other journals to join us in this initiative. We hope that our action inspires the community, including researchers, research funders, and research institutions, to recognize the benefits of published peer review reports for all parts of the research system.

Learn more at ASAPbio .