Background and objective
Loneliness is associated with increased rates of morbidity and mortality, and is a growing public health concern in later life. This study aimed to produce an evidence-based estimate of the prevalence of loneliness amongst older people (aged 60 years and above).
Study design and setting
Systematic review and random-effects meta-analysis of observational studies from high income countries 2008 to 2020, identified from searches of five electronic databases (Medline, EMBASE, PsychINFO, CINAHL, Proquest Social Sciences Premium Collection). Studies were included if they measured loneliness in an unselected population.
Thirty-nine studies reported data on 120,000 older people from 29 countries. Thirty-one studies were suitable for meta-analysis. The pooled prevalence estimate of loneliness was 28.5% (95%CI: 23.9% - 33.2%). In twenty-nine studies reporting loneliness severity, the pooled prevalence was 25.9% (95%CI: 21.6% - 30.3%) for moderate loneliness and 7.9% (95%CI: 4.8% - 11.6%) for severe loneliness (z = -6.1, p < 0.001). Similar pooled prevalence estimates were observed for people aged 65–75 years (27.6%, 95%CI: 22.6% - 33.0%) and over 75 years (31.3%, 95%CI: 21.0% - 42.7%, z = 0.64, p = 0.52). Lower levels of loneliness were reported in studies from Northern Europe compared to South and Eastern Europe.
Loneliness is common amongst older adults affecting approximately one in four in high income countries. There is no evidence of an increase in the prevalence of loneliness with age in the older population. The burden of loneliness is an important public health and social problem, despite severe loneliness being uncommon.
Citation: Chawla K, Kunonga TP, Stow D, Barker R, Craig D, Hanratty B (2021) Prevalence of loneliness amongst older people in high-income countries: A systematic review and meta-analysis. PLoS ONE 16(7): e0255088. https://doi.org/10.1371/journal.pone.0255088
Editor: Muhammad Shahzad Aslam, Xiamen University - Malaysia Campus: Xiamen University - Malaysia, MALAYSIA
Received: April 30, 2021; Accepted: July 9, 2021; Published: July 26, 2021
Copyright: © 2021 Chawla et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the paper and its Supporting Information files.
Funding: This work was supported by the National Institute for Health Research (NIHR) School for Primary Care Research (SPCR, 2016DS to D.S). The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Loneliness is acknowledged as a public health concern, particularly in later life . It is has been defined as an undesirable subjective experience, arising from unfulfilled intimate and social needs . Loneliness is accepted to have a negative impact on quality of life and wellbeing  and the overall risk to health from loneliness has been compared to that of smoking and obesity . Evidence is growing for an association with a wide range of adverse mental  and physical health outcomes, including dementia , long term conditions such as frailty , cardiovascular disease  and premature mortality . Recent studies have also suggested that lonely older people are more likely to be living with multiple health conditions , and that loneliness may be linked with increased use of some health and social care services .
Tackling loneliness is already a policy imperative in many countries, and England and Wales introduced a dedicated strategy in 2018 . Yet despite this, our understanding of the size of the public health problem is limited [13, 14]. To date, reviews of the evidence have been unsystematic , selective [16, 17], or rapid in their approaches . They report prevalence figures of between 2% and 34% for older people with a suggestion that chronic loneliness may affect 10 to 15% of people at all ages . Studies from the UK, New Zealand and elsewhere point to a U-shaped distribution in the prevalence of loneliness across the life-course, but with little agreement over the age at which peaks and troughs in loneliness may be observed [19–21]. There is a perception that loneliness is becoming more common over time, with possible causes being changes in living arrangements, a rise in solitary living , smaller families , the loss of community resources such as libraries and post offices and the advent of the internet . However, analyses of repeated cross-sectional studies in the UK (1946 to1999) , and Sweden (1994 to 2014)  suggest that the prevalence of loneliness has remained stable over time.
A sound knowledge of the epidemiology of loneliness is essential to support intervention design and development, and service planning. This review aims to determine the prevalence of loneliness amongst the general population of older people in high income countries. Where data are available, it will also seek to identify any differences in the prevalence of loneliness by age amongst older people.
Materials and methods
This review adopted methods recommended by the Centre for Reviews and Dissemination , reporting follows PRISMA guidance . A protocol was registered prospectively with PROSPERO (CRD42017060472).
Five electronic databases were searched from 2008 to July 2020 (Medline, Embase, PsychINFO, CINAHL, Social Sciences Premium Collection), using a search strategy developed and tailored for each database with an information scientist (data in S1 File). Thesaurus headings and key words related to loneliness and older people were used. Grey literature (The Campaign to End Loneliness, Gulbenkian Foundation, and AGE UK websites), ageing journals and reference lists of included studies were also searched. No date or country restrictions were applied at this stage, but we restricted the search to English language material.
Studies were included if they provided cross-sectional data on any measure of loneliness within a defined population of adults from high income countries, defined by the World Bank ; published between 2008 and 2020 aged 60 years and above. Studies focusing on institutionalised populations only were excluded, however because we were looking at the prevalence amongst older people, studies with a small proportion of people in care homes were included. Highly selected samples, such as groups of patients with a single disease (for example heart disease), specific characteristics, or role (e.g., caregivers) were excluded.
Screening and data extraction
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 . 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.
Data were extracted into a bespoke form, developed using relevant guidance . In addition to standard study and population demographic data, information was extracted on the measurement tools/scales, cut-offs used to define loneliness and frequency or intensity of loneliness. Authors were contacted for further information, where necessary, and one response received.
Classification of loneliness
Loneliness was defined by any self-reported measure of loneliness, ranging from a single items question to a multi-item tool . There are numerous tools available to assess loneliness, and if studies measured the number or proportion of people who were experiencing loneliness, irrespective of the loneliness measure used, the study was included.
The experience of loneliness can vary in intensity and frequency within the same individual during their lifetime and therefore a point prevalence may be difficult to interpret. It is believed that both situational and chronic loneliness are associated with adverse health conditions . Therefore, this review sought to measure the prevalence of any feelings of loneliness. For this study we categorised people as lonely if they answered positively to feelings of loneliness such as feeling lonely ‘often’ or ‘always’ or ‘sometimes.’ If they gave a negatively worded response such as ‘not’ lonely or ‘not very’ lonely this was categorised as not lonely.
For those studies which provided the number of participants reporting different intensities or frequencies of loneliness, participants reporting the highest category of loneliness possible in the study were considered ‘severely’ lonely in this review.
Risk of bias
Risk of bias was assessed using the standardised the Joanna Briggs Checklist for Studies Reporting Prevalence Data ; 30% of studies were assessed by two researchers. In this review, risk of bias was judged to be low, moderate, or high if ≤2, 3–4, or 5+ criteria respectively were not fulfilled. However, no studies were excluded because of risk scores.
Where suitable statistical data were reported, we conducted a pooled meta-analysis using Metafor  in R Core Team . Heterogeneity was assessed with the I2 statistic, with a value over 50% taken to indicate substantial heterogeneity . Random-effects meta-analysis was conducted with pre-specified subgroups to explore potential sources of heterogeneity. Subgroup comparisons were made using a Wald type estimator . Data were transformed using the Freeman-Tukey double arcsine transformation .
Thirty-nine studies were included in this review, after screening of 12,849 titles/abstracts and review of 139 full texts. 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. The study selection process is shown in Fig 1; details and main findings of the included studies in Table 1.
The included studies provided information on approximately 140,000 older people (age 60 years and over) from 30 countries. Most of the research was conducted in European countries [7, 25, 39–59, 72, 73] with four from the USA [64–67], two from each of Israel [60, 61] and New Zealand [19, 62] and single studies from Singapore  and Australia . Four studies provided estimates of prevalence across a large proportion of Europe [69–71, 73]. Living circumstances were reported in seven studies; people living in institutions were included in four studies [25, 39, 49, 50], excluded in three [46, 52, 61] and no data available from the remainder.
All thirty-nine studies were cross-sectional in design. Data were collected by face-to-face interview [7, 19, 25, 39, 41, 42, 46, 47, 49–55, 57–61, 64, 67–71], postal questionnaires [40, 43–45, 48, 56, 62, 63, 73] and online questionnaires [65, 66, 72].
Measurement of loneliness
Loneliness was measured using either a single item question, or one of two well established scales. Eight studies used the De Jong Gierveld scale [49, 50, 54, 56, 62, 68, 73], and all but one study  employed the longer 11-point version. The UCLA loneliness measure was used in five studies [7, 65, 66, 68, 72]. Respondents were asked to consider experiences of loneliness in the previous week [63, 64, 69, 71] four weeks [19, 61] or year . In eleven studies, no time frame was specified [25, 39–41, 43, 44, 46, 47, 50, 51, 60]. One study used an 11-tem Loneliness Scale designed for large surveys .
Risk of bias
Using the Joanna Briggs Checklist for Studies Reporting Prevalence Data, the majority (28 out of 39) of studies were judged to have a low risk of bias [7, 25, 39–45, 50–53, 55–59, 61, 64, 66, 67, 69–73]. Ten studies were judged to be moderate risk [19, 46–48, 54, 60, 62, 63, 65, 68] and only one study based in the UK was judged to be at high risk of bias . The potential for bias was identified in 4 out of 9 domains, mainly due to not having enough participants to address the target population. The domains with the greatest risk of bias relate to coverage bias (domain 5) and response rate (domain 9), as detailed in, Fig 2, principally due to the absence of sufficient information on which to make a judgement.
Gender differences in prevalence of loneliness.
Nine studies reported the prevalence of loneliness by gender. Three of the nine studies found no gender differences [62, 68]. Six studies reported that females were more likely than males to be lonely. This was attributed to gender differences in the distribution of risk factors such as living arrangements, marital status, and self-rated health [6, 41, 43, 45, 50, 61].
Two articles reported on loneliness within single sex populations [46, 54]. A study in Oslo with 307 females aged over 75 years and living at home, reported that one third of the female participants were lonely at least some of the time . In Amsterdam, Julsing and colleagues’  study with men aged 64–84 years found a prevalence of loneliness of 43%.
Geographical variation in prevalence of loneliness.
Although this study was not designed to investigate geographical differences, we did observe variation in the reported prevalence of loneliness within and between countries. Figures in European countries ranged from 11.6% to 56.0%. North American studies reported 19.3% to 32.0%; Israel 17.9% to 38.1%, New Zealand 9.6% to 52%, and Singapore 55%. Some of this variation may be due to the differences in the cut off points for loneliness measurements, data collection methods and sample sizes. International comparative studies describe consistent patterns, with reported prevalence higher in Mediterranean countries (e.g., Italy and Portugal) compared to northern European countries (UK, Ireland, Scandinavia) , but not those of the former Soviet Union . Further research to better understand these geographical differences might support learning or understanding from countries with lower prevalence.
Thirty-one of the thirty-nine studies provided data suitable for pooling (Fig 3). The pooled estimate of the prevalence of loneliness amongst people aged over 65 years in high income countries, was 28.5% (95%CI: 23.9% to 33.2%). There was a substantial degree of heterogeneity (I2 99.7%, Q-test p < 0.001), 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.
Two additional a priori specified subgroup analyses were conducted. The first compared people reporting severe loneliness to those reporting moderate loneliness. Twenty-nine studies provided information on loneliness severity (moderate vs severe). Pooled estimates were 7.9% (95%CI: 4.8% to 11.6%) for people reporting severe loneliness, and 25.9% (95%CI: 21.6% to 30.3%) for moderate loneliness (z = -6.1, p < 0.001 for the comparison).
The point estimate for the pooled estimate of loneliness prevalence in people aged over 75 (31.3%, 95%CI: 21.0% to 42.7%) was higher than for people age 65–75 (27.6%, 95%CI: 22.6% to 33.0%), but the confidence intervals for these estimates were wide and overlapping and the comparison was not conventionally statistically significant (z = 0.64, p = 0.52).
To our knowledge, this is the first systematic review to present pooled estimates of loneliness amongst older adults living in high income countries. 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 65–75. However, there was some evidence that the prevalence of loneliness is lowest in northern European countries and higher in Mediterranean countries and Eastern Europe.
Comparison with other work
The prevalence estimates from our meta-analysis sit within the previously published ranges, which are wide. 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. In addition, published prevalence rates have been most consistent for very frequent or severe loneliness amongst the older population, at between 5 and 13% . The proportion of older people who reported feeling at least sometimes lonely showed more variation, at 17% to 34%. These findings held true when data from multiple countries were examined, in a review published in 1996 which reported a prevalence of severe loneliness between 2% and 16% and moderate loneliness between 7% and 42% . A recent review of loneliness in care home residents estimated the mean prevalence of moderate and severe loneliness to be higher than the general older population (at 61% and 35%), but confidence intervals are wide .
Strengths and limitations
This review brings together, for the first time, data from studies of the prevalence of loneliness in unselected older populations. Our approach was systematic, using validated methods. We restricted the review to studies from high-income countries to reduce some of the cultural and socioeconomic variation between study populations. However, we acknowledge that a focus on English language publications may have led us to overlook some relevant material, although we expect that the impact on overall findings would be minimal. We sought to identify differences between people in early and later old age, but data were not available to support this.
Inclusion of all measures of loneliness used in the published studies, different measurement schedules and intensity of loneliness produced a heterogeneous group of studies. 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. However, we set out to produce a comprehensive review and at present, our understanding of the natural history of different experiences of loneliness (e.g., chronic versus more intense loneliness) is insufficient to justify excluding individual studies.
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.
Overall, we have shown that loneliness is a common experience in later life, though severe loneliness affects only a small proportion of the population. As loneliness is both distressing and associated with adverse outcomes, it is a legitimate target for action. There are numerous potential risk factors for loneliness, including personal characteristics (age, gender, ethnicity), health, disability, life events (bereavement, retirement), living circumstances and social resources (single person households, social networks, presence of a confidante), and geographical area (social disadvantage, perception of crime) [81, 82]. We have reported prevalence according to a small number of factors that are not mutable. Nevertheless, they provide useful information for directing health and societal interventions to people at highest risk. Work to identify the characteristics of people affected by severe loneliness and the aetiological factors, is needed to complement any interventions to positively impact population level experiences of loneliness. Our work also emphasises the need to deepen our understanding of effective strategies to prevent or ameliorate loneliness. There is evidence that group interventions many be more effective than individual initiatives, but the range of interventions that have been tested is narrow, with a strong focus on befriending and telephone support . The appropriateness of health or social services responses to this problem is far from clear.
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.
The authors wish to thank Sarah Khan and Aalya Al-Assaf for their contributions for title and abstract screening and data extraction.
- 1. Forbes A. Caring for Older People: Loneliness. British Medical Journal. 1996;313(7053):352. pmid:8760749
- 2. Peplau LA, Perlman D. Loneliness: A Sourcebook of Current Theory, Research and Practice, Perspectives on loneliness. 1982. New York: John Wiley; [1–17]. Available from: http://www.peplaulab.ucla.edu/Peplau_Lab/Publications_files/Peplau_perlman_82.pdf.
- 3. Kearns A, Whitley E, Tannahill C, Ellaway A. Loneliness, social relations and health and well-being in deprived communities. Psychology, Health & Medicine. 2015;20(3):332–44. pmid:25058303
- 4. Holt-Lunstad J, Smith TB, Layton JB. Social relationships and mortality risk: a meta-analytic review. PLOS Medicine. 2010;7(7):e1000316. pmid:20668659
- 5. Meltzer H, Bebbington P, Dennis MS, et al. Feelings of loneliness among adults with mental disorder. Social Psychiatry and Psychiatric Epidemiology. 2013;48(5):5–13. pmid:22570258
- 6. Holwerda TJ, Deeg DJH, Beekman ATF, et al. Feelings of loneliness, but not social isolation, predict dementia onset: results from the Amsterdam Study of the Elderly (AMSTEL). Journal of Neurology, Neurosurgery & Psychiatry. 2014;85(2):135–42.
- 7. Gale CR, Westbury L, Cooper C. Social isolation and loneliness as risk factors for the progression of frailty: the English Longitudinal Study of Ageing. Age and ageing. 2018;47(3):392–7. pmid:29309502
- 8. Valtorta NK, Kanaan M GS, Ronzi S, Hanratty B. Loneliness and social isolation as risk factors for coronary heart disease and stroke: systematic review and meta-analysis of longitudinal observational studies. Heart. 18/04/2016 ed2016. p. 1009–16. pmid:27091846
- 9. Holt-Lunstad J, Smith TB, Baker M, Harris T, Stephenson D. Loneliness and social isolation as risk factors for mortality: a meta-analytic review. Perspectives on Psychological Science. 2015;10(2):227–37. pmid:25910392
- 10. Taube E, Kristensson J, S., et al. Loneliness and health care consumption among older people. SCAND J CARING SCI. 2015;29(3):435–43. pmid:24826811
- 11. Valtorta NK, Moore DC, Barron L, Stow D, Hanratty B. Older adults’ social relationships and health care utilization: a systematic review. American journal of public health. 2018;108(4):e1. pmid:29470115
- 12. Department for Digital Culture Media and Sport. A connected society: A strategy for tackling loneliness-laying the foundations for change London: HM Government; 2018 [Available from: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/748212/6.4882_DCMS_Loneliness_Strategy_web.pdf.
- 13. Cacioppo JT, Cacioppo S. The growing problem of loneliness. The Lancet. 2018;391(10119):426. pmid:29407030
- 14. 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;105(5):1013–9. pmid:25790413
- 15. Victor C, Scambler S, Bond J, Bowling A. Being alone in later life: Loneliness, social isolation and living alone. Reviews in Clinical Gerontology. 2000;10(4):407–17.
- 16. Luanaigh CO., Lawler BA. Loneliness and the health of older people. International Journal of Geriatric Psychiatry. 2008;23(12):1213–21. pmid:18537197
- 17. Ong AD, Uchino BN, Wethington E. Loneliness and health in older adults: a mini-review and synthesis. Gerontology. 2016;62(4):443–9. pmid:26539997
- 18. Jopling K., Sserwanja I. Loneliness across the lifecourse: The Gulbenkian foundation; 2016 [Available from: https://content.gulbenkian.pt/wp-content/uploads/sites/18/2016/07/01175346/27-07-16-Loneliness-Across-the-Life-Course-Full-Report.pdf.
- 19. Ministry of Social Development. The Social Report 2016 Wellington: New Zealand Government; 2016 [Available from: http://socialreport.msd.govt.nz/social-connectedness/loneliness.html.
- 20. Pinquart M, Sorensen S. Influences on Loneliness in Older Adults: A Meta-Analysis. Basic and Applied Social Psychology. 2001;23(4):245–66.
- 21. Victor CR, Yang K. The Prevalence of Loneliness Among Adults: A Case Study of the United Kingdom. The Journal of Psychology. 2012;146(1–2):85–104. pmid:22303614
- 22. Office for National Statistics. Families and Households: 2017: Office for National Statistics; 2017 [Available from: https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/families/bulletins/familiesandhouseholds/2017.
- 23. Griffin J. The Lonely Society: Mental Health Foundation; 2010 [Available from: https://www.mentalhealth.org.uk/sites/default/files/the_lonely_society_report.pdf.
- 24. Victor CR, Scambler SJ, Shah S, et al. Has loneliness amongst older people increased? An investigation into variations between cohorts. Ageing and Society. 2002;22(5):585–97.
- 25. Dahlberg L, Agahi N, Lennartsson C. Lonelier than ever? Loneliness of older people over two decades. Archives of Gerontology & Geriatrics. 2018;75:96–103. pmid:29220739
- 26. Centre for Reviews and Dissemination. Systematic Reviews: CRD’s guidance for undertaking reviews in health care. York: CRD; 2009.
- 27. Liberati A, Altman DG, Tetzlaff J, et al. The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate healthcare interventions: explanation and elaboration. BMJ. 2009;339. pmid:19622552
- 28. World Bank Group. High Income: World Bank Group; 2021 [Available from: https://data.worldbank.org/income-level/high-income.
- 29. Ouzzani M HH, Fedorowicz Z, Elmagarmid A. Rayyan- a web and mobile app for systematic reviews. Systematic Reviews. 2016;5(1).
- 30. The Joanna Briggs Institute. Joanna Briggs Institute Reviewers Manual:2014 edition/supplement: The Joanna Briggs Institute; 2014 [Available from: http://joannabriggs.org/assets/docs/sumari/ReviewersManual_The-Systematic-Review-of-Prevalence-and-Incidence-Data.pdf.
- 31. 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). pmid:27091822
- 32. Shiovitz-Ezra S, Ayalon L. Situational versus chronic loneliness as risk factors for all-cause mortality. International Psychogeriatrics. 2010;22(3):455–62. pmid:20003631
- 33. Joanna Briggs Institute. Critical Appraisal Tools: Joanna Briggs Institute; 2018 [Available from: http://joannabriggs.org/research/critical-appraisal-tools.html.
- 34. Wolfgang Viechtbauer. Conducting meta-analyses in R with the metafor package. Journal of Statistical Software. 2010;36(3):1–48.
- 35. Pinheiro J BD, DebRoy S, Sarkar D, R Core Team (2021). nlme: Linear and Nonlinear Mixed Effects Models. [R package version 3.1–152]. 2021 [19 July 2018]. Available from: https://cran.r-project.org/package=nlme.
- 36. Deeks JJ HJ, Altman DG Chapter 9: Analysing data and undertaking meta-analyses. 2011. In: Cochrane Handbook for Systematic Reviews of Interventions Version 51 [Internet]. The Cochrane Collaboration. Available from: www.handbook.cochrane.org.
- 37. Rubio-Aparicio M, López-López JA, Viechtbauer W, et al. Testing categorical moderators in mixed-effects meta-analysis in the presence of heteroscedasticity. The Journal of Experimental Education. 2020;88(2):288–310.
- 38. Barendregt JJ, Doi SA, Lee YY, Norman RE, Vos T. Meta-analysis of prevalence. Journal of Epidemiology and Community Health. 2013;67(11):974. pmid:23963506
- 39. Nyqvist F, Cattan M, Conradsson M, Nasman M, Gustafsson Y. Prevalence of loneliness over ten years among the oldest old. SCAND J PUBLIC HEALTH. 2017;45(4):411–8. pmid:28381194
- 40. Djukanovic I, Sorjonen K, Peterson U. Association between depressive symptoms and age, sex, loneliness and treatment among older people in Sweden. Aging & Mental Health. 2015;19(6):560–8.
- 41. Aartsen M, Jylhä M. Onset of loneliness in older adults: results of a 28 year prospective study. European Journal of Ageing. 2011;8(1):31–8. pmid:21475393
- 42. Heikkinen RL, Kauppinen M. Mental well-being: a 16-year follow-up among older residents in Jyvaskyla. Archives of Gerontology & Geriatrics. 2011;52(1):33–9. pmid:20207429
- 43. Eloranta S, Arve S, Isoaho H, Lehtonen A, Viitanen M. Loneliness of older people aged 70: a comparison of two Finnish cohorts born 20 years apart. Archives of Gerontology & Geriatrics. 2015;61(2):254–60. pmid:26143336
- 44. Tilvis RS, Routasalo P, Karppinen H, et al. Social isolation, social activity and loneliness as survival indicators in old age a nationwide survey with a 7-year follow-up. European Geriatric Medicine. 2011;3(1).
- 45. Lasgaard M, Friis K, Shevlin M. "Where are all the lonely people?" A population-based study of high-risk groups across the life span. SOC PSYCHIATRY PSYCHIATR EPIDEMIOL. 2016;51(10):1373–84. pmid:27571769
- 46. Bergland A, Engedal K. Living arrangements, social networks, health, mobility, and balance of older women. Physical & Occupational Therapy in Geriatrics. 2011;29(2):90–101.
- 47. Nicolaisen M, Thorsen K. Loneliness among men and women—a five-year follow-up study. Aging & Mental Health. 2014;18(2):194–206. pmid:23895066
- 48. Tomstad S, Dale B, Sundsli K, Sævareid HI, Söderhamn U. Who often feels lonely? A cross-sectional study about loneliness and its related factors among older home-dwelling people. International Journal of Older People Nursing. 2017;12(4):n/a-n/a. pmid:28752653
- 49. Scharf T, de Jong Gierveld J. Loneliness in urban neighbourhoods:an Anglo-Dutch comparison. European Journal of Ageing. 2008;5(2):103–15. pmid:28798565
- 50. Brittain K, Kingston A, Davies K, et al. An investigation into the patterns of loneliness and loss in the oldest old–Newcastle 85+ Study. 2017;37(1):39–62.
- 51. Victor CR, Bowling A. A longitudinal analysis of loneliness among older people in Great Britain. Journal of Psychology: Interdisciplinary and Applied.146(3):313–31. pmid:22574423
- 52. Dahlberg L, McKee KJ. Correlates of social and emotional loneliness in older people: evidence from an English community study. Aging & Mental Health. 2014;18(4):504–14. pmid:24251626
- 53. Thomas J. Insights into Loneliness, Older People and Well-being, 2015: Office for National Statistics; 2015 [Available from: https://backup.ons.gov.uk/wp-content/uploads/sites/3/2015/10/Insights-into-Loneliness-Older-People-and-Well-being-2015.pdf.
- 54. Julsing JE, Kromhout D, Geleijnse JM, Giltay EJ. Loneliness and All-Cause, Cardiovascular, and Noncardiovascular Mortality in Older Men: The Zutphen Elderly Study. American Journal of Geriatric Psychiatry. 2016;24(6):475–84.
- 55. Holwerda TJ, Beekman AT, Deeg DJ, et al. Increased risk of mortality associated with social isolation in older men: only when feeling lonely? Results from the Amsterdam Study of the Elderly (AMSTEL). Psychological Medicine. 2012;42(4):843–53. pmid:21896239
- 56. Honigh-de Vlaming R, Haveman-Nies A, Bos-Oude Groeniger I, de Groot L, van ‘t Veer P. Determinants of Trends in Loneliness Among Dutch Older People Over the Period 2005–2010. Journal of Aging & Health. 2014;26(3):422–40. pmid:24452851
- 57. Tabue Teguo M, Simo-Tabue N, Stoykova R, et al. Feelings of Loneliness and Living Alone as Predictors of Mortality in the Elderly: The PAQUID Study. Psychosomatic Medicine. 2016;78(8):904–9. pmid:27583712
- 58. Golden J, Conroy RM, Bruce I, et al. Loneliness, social support networks, mood and wellbeing in community-dwelling elderly. International Journal of Geriatric Psychiatry. 2009;24(7):694–700. pmid:19274642
- 59. Molloy GJ, McGee HM, O’Neill D, Conroy RM. Loneliness and emergency and planned hospitalizations in a community sample of older adults. JAmGeriatrSoc. 2010;58(8):1538–41.
- 60. Stessman J, Shimshilashvili I, Jacobs JM. Loneliness from age 70 to 85: A medical or social problem? JAmGeriatrSoc.1:S141–S2.
- 61. Cohen-Mansfield J, Shmotkin D, Goldberg S, et al. Loneliness in old age: longitudinal changes and their determinants in an Israeli sample. International Psychogeriatrics. 2009;21(6):1160–70. pmid:19785916
- 62. La Grow S, Neville S, Alpass F, Rodgers V. Loneliness and self-reported health among older persons in New Zealand. Australasian Journal on Ageing. 2012;31(2):121–3. pmid:22676172
- 63. Franklin A., Tranter B. Loneliness in Australia Hobart, Tasmania: University of tasmania: Housing and Community Research Unit; 2008 [Available from: http://apo.org.au/system/files/4070/apo-nid4070-53476.pdf.
- 64. Theeke L. Predictors of Loneliness in U.S. Adults over Age Sixty-Five. Archives of Psychiatric Nursing. 2009;23(5):387–96. pmid:19766930
- 65. American Association Of Retired People. Loneliness among older Adults: A national Survey o Adults 45+ Washington DC: AARP; 2010 [Available from: https://assets.aarp.org/rgcenter/general/loneliness_2010.pdf.
- 66. Hawkley LC, Wroblewski K, Kaiser T, Luhmann M, Schumm LP. Are US older adults getting lonelier? Age, period, and cohort differences. Psychology and Aging. 2019;34(8):1144. pmid:31804118
- 67. Pavela G, Kim Y-i, Salvy S-J. Additive effects of obesity and loneliness on C-reactive protein. PloS one. 2018;13(11):e0206092. pmid:30439985
- 68. Lim KK, Chan A. Association of loneliness and healthcare utilization among older adults in Singapore. Geriatrics and Gerontology International.17(11):1789–98. pmid:28060447
- 69. Yang K, Victor C. Age and loneliness in 25 European nations. Ageing and society.31(8):1368–88.
- 70. Hansen T, Slagsvold B. Late-Life Loneliness in 11 European Countries: Results from the Generations and Gender Survey. Social Indicators Research.129(1):445–64.
- 71. Sundström G, Fransson E, Malmberg B, Davey A. Loneliness among older Europeans. European Journal of Ageing. 2009;6(4):267–75. pmid:28798610
- 72. Lara E, Caballero FF, Rico‐Uribe LA, et al. Are loneliness and social isolation associated with cognitive decline? International journal of geriatric psychiatry. 2019;34(11):1613–22. pmid:31304639
- 73. Tan SS, Fierloos IN, Zhang X, et al. The association between loneliness and health related quality of life (HR-QoL) among community-dwelling older citizens. International journal of environmental research and public health. 2020;17(2):600. pmid:31963427
- 74. World Atlas. The Countries of Northern Europe: World Atlas; 2018 [Available from: https://www.worldatlas.com/articles/which-countries-are-considered-to-be-part-of-northern-europe.html.
- 75. World Atlas. Former Soviet Union Countries: World Atlas; 2018 [Available from: https://www.worldatlas.com/articles/what-countries-made-up-the-former-soviet-union-ussr.html.
- 76. Iecovich E, Jacobs JM, Stessman J. Loneliness, social networks, and mortality: 18 years of follow-up. The International Journal of Aging and Human Development. 2011;72(3):243–63. pmid:21834390
- 77. Heinrich LM, Gullone E. The clinical significance of loneliness: A literature review. Clinical Psychology Review. 2006;26(6):695–718. pmid:16952717
- 78. Wenger GC, Davies R, Shahtahmasebi S, Scott A. Social isolation and loneliness in old age: review and model refinement. Ageing and Society. 1996;16(3):333–58.
- 79. Gardiner C, Laud P, Heaton T, Gott M. What is the prevalence of loneliness amongst older people living in residential and nursing care homes? A systematic review and meta-analysis. Age and Ageing. 2020;49(5):748–57. pmid:32396600
- 80. Patterson AC, Veenstra G. Loneliness and risk of mortality: A longitudinal investigation in Alameda County, California. Social Science & Medicine. 2010;71(1):181–6. pmid:20417589
- 81. de Jong Gierveld J,. A review of loneliness: concept and definitions, determinants and consequences. Reviews in Clinical Gerontology. 1998;8(1):73–80.
- 82. Victor CR, Scambler SJ, Bowling A, Bond J. The prevalence of, and risk factors for, loneliness in later life: a survey of older people in Great Britain. Ageing and Society. 2005;25(6):357–75.
- 83. Windle K, Francis J, Coomber C. Preventing loneliness and social isolation: interventions and outcomes. London: Social Care Institute for Excellence; 2011.