Table 2 Study Population

Effective

Collins 2006 [25]

Evaluate the effectiveness of an educational intervention on older adults’ mastery, loneliness and stress

USA

73.2(8.6)

[52–93]

20%

68%

28% did not complete high school; 21% hold degree

70% household income <$19,999 per year.

Creswell 2012 [26]

Evaluate the effect of Mindfulness-Based Stress Reduction program on loneliness

USA

I = 64.4(6.0); WL = 65.2(8.0)

T = 20%;

I = 15%;

WL = 25%

T = 65%; I = 65%; WL = 65%

Total = 73%; I = 70%; C = 75% college degree /graduate work

T(I,WL): 35%(50,20) retired; 3% (0,5) unemployed; 60%(50,70) employed. Mean(SD): BMI = 25.2(4); MMSE I = 28.0(2), WL = 27.8(2)

Gaggioli 2014 [30]

Evaluate the effects of intergenerational reminiscence on cognitively unimpaired elderly participants focussing on self-esteem, loneliness and isolation, and quality of life

Italy

67.5(6.0)

NR

NR

NR

NR

Larsson 2016 [38]

Evaluate the effects of a social internet-based intervention for older adults vulnerable to loneliness

Sweden

T = 71.2[61–89]; group 1 = 73.4[66–89];

group 2 = 69.0[61–76]

T = 20%; group 1 = 20%; group 2 = 20%

NR

T = 57%;

group 1 = 47%; group 2 = 67%

university degree

T(group 1,group 2): 30%(33, 27) married/cohabiting; 87%(93,80) participate in offline social activities at least once a week; 70%(67,73) use email at least once a week

Ehlers 2017 [27]

Examine the effect of social support and stress on change in perceived loneliness after an exercise intervention

USA

65.4(4.6)

32%

84%

59% college graduate

59% married. Mean(SD) BMI = 31.0(5.6)

Bouwman 2017 [22]

Investigate whether an online friendship enrichment program can alleviate loneliness

The Netherlands

61.6(7.2)

[50–86]

22%

NR

Median level = 8 [1 = primary − 9 = university]

40% have a partner; 74% have children; 72% good health

Cohen-Mansfield 2018 [24]

Understand the efficacy of the I-SOCIAL intervention which addresses social integration barriers for loneliness in old age

Israel

I = 76.6(6.8); C = 79.0(6.6)

I = 21%; C = 17%

NR

I/C = 14 mean years education

I = 15%(C = 14%) married. Mean values I(C): children = 2.2(1.6), MMSE = 27.7(27.9), number medical diagnoses = 2.8(2.6), subjective health [range 1–4] = 2.4(2.2)

Hwang 2019 [32]

Develop an understanding of the experience of living with loneliness and social isolation

Canada

76.6[65–88]

13%

NR

NR

69% live alone; 13% caregivers

Kall 2020 [33]

Investigate the long-term effects of an internet-administered programme based on CBT principles

Sweden

T = 47.2(17.6); I = 45.6(16.7); C = 48.8(18.4)

T = 29%;

I = 28%; C = 30%

NR

T = 66%; I = 65%; C = 67% university degree

T(I,C): partner/married 32%(33,30); previous treatment for mental illness 47%(53,41); no use 62%(58,65), previous use 12%(11, 14), ongoing use 26%(31,22) of psychopharmaceutic medication

Ghanbari 2021 [31]

Investigate the effect of a program promoting coping and assessment processes on loneliness in children

Iran

I = 10.6(1.4);

C = 10.2(1.3)

NR

NR

100% in school grades 3–6

I(C): 20%(27) only children; 54%(43) oldest child

Fong 2021 [29]

Evaluate the effectiveness of a community-based intervention designed to increase neighbourhood identification and reduce loneliness

Australia

18+

17%

NR

51% university degree

20% from most disadvantaged areas, 43% average SES, 35% most advantaged areas

Kall 2021 [34]

Investigate the efficacy of two internet-based interventions for loneliness based on cognitive behavioural therapy (CBT) and interpersonal psychotherapy (IPT)

Sweden

T = 47.5(16.4); IPT = 49.7(16.4); CBT = 47.2(15.9); WL = 43.9(17.1)

T = 24%; IPT = 16%; CBT = 28%; WL = 32%

NR

T = 69%; IPT = 74%; CBT = 62%; WL = 77% university degree

T(IPT,CBT,WL): 18%(21,22,6) married/cohabit; 65%(68,56,79) live alone; 68%(68,68,71) employed/student; 57%(63,56,44) previous mental health treatment; 46%(53,40,44) previous/current psychotropic medication; 45%(53,36,47) loneliness from an event. Mean(SD): years duration of loneliness IPT = 11(12), CBT = 12(16), WL = 11(12); age lonely onset IPT = 27(22), CBT = 25(19), WL = 27(19).

Nazari 2021 [39]

Determine the impact of a social participation educational program on the feeling of loneliness for the elderly

Iran

Men:

I = 46.0(38.7); C = 57(47.5)

Women:

I = 73 (61.3); C = 63(52.5)

I = 39%; C = 48%

NR

NR

I(C): 81%(83) married; 19%(18) widow; 8%(7) live alone; 53%(41) unemployed, 60%(52) housewife, 5%(7) employed

Kotwal 2021 [36]

Assess the effect of a peer intervention addressing loneliness in low-income older adults

USA

Median = 70.0, IQR[66–76], range[59–96]

58%

(66% in qualitative interview)

42%

(33% in qualitative interview)

12% college graduate or more

14% married/partner; 88% live alone; 18% LGBT; 62% English primary language; 11% veterans; 36% at least 1 functional impairment; 36% depression; 66% high loneliness.

Can’t tell if effective

Steven 2000 [43]

Evaluate an educational friendship program for older women to alleviate loneliness

The Netherlands

I = 63.4; C = 69.8

0%

NR

NR

I = 25% married; 38% widowed; average 3 children (C = 2 children). Total = 75% live alone

Rolandi 2020 [40]

Investigate the long-lasting

effect of Social Network Site use training in oldest-old adults on loneliness in the context of COVID-19 quarantine

Italy

T = 81.8(1.4); trained=

82.0(1.6); untrained = 81.6(1.2)

T = 48%; trained = 47%; untrained = 49%

NR

Mean(SD) education: T = 9(3); trained = 9(3); untrained = 9(4)

T(trained, untrained): 37%(38,36) live alone. T(trained, untrained) mean ± SD GDS score = 1.9 ± 1.9 (2.0 ± 1.9, 1.8 ± 2.0); MMSE score = 28.4 ± 1.5 (28.3 ± 1.4, 28.4 ± 1.5)

Caputi 2021 [23]

Assess the effects of theory of mind training on loneliness

Italy

9.7(0.9)

[9, 10]

NR

NR

NR

Median socioeconomic status = 6[range 2–9]

Kanter 2021 [35]

Investigate whether a brief mobile based intervention for social relationships can decrease loneliness and improve relationship quality during the COVID-19 pandemic

USA

T = 41.7(15.0); I = 41.2(15.1); C = 42.3(14.9)

T = 18%; I = 20%; C = 17%

T = 77%; I = 76%; C = 78%

NR

T(I,C): 44%(43, 46) married; 51%(54,49) no children; never diagnosed with major depressive disorder 72%(73,71), OCD 94%(94, 94), generalised anxiety disorder 68%(70,66), social anxiety disorder; 89%(90,88)

Shapira 2021 [42]

Explore the effects of a short-term digital group intervention aimed at providing cognitive behavioural and mindfulness tools and skills to reduce loneliness

Israel

T = 72[65–90]; I = 72.1(5.3); C = 71.7(6.8)

T = 20%; I = 19%; C = 22%

NR

T = 71%; I = 76%; C = 59% tertiary education

T(I,C): 37%(38, 35) live alone

Not effective

Fields 2021 [28]

Evaluate the effect of a community-based digital intervention on loneliness, perceived social support, and technology use in isolated older adults

USA

T = 75.0(7.9);

I = 74.0(8.5); WL = 76.0(7.4)

T = 47%;

I = 52%;

WL = 43%

T = 60%; I = 67%; WL = 53%

T = 45%; I = 50%; WL = 40% completed high school or less

T(I,WL): 69%(77,62) household income <$20,000 per year; 13%(12,13) limited English proficiency; 32%(33,30) no cell phone; 54%(56, 53) fair or poor mental health; 21%(29,14) frequent mental distress; 45%(46,44) frequent physical distress; 35%(41,31) frequent functioning interference

Sandu 2021 [41]

Explore the impact of a Good Neighbour Program on reducing loneliness in older adults during the COVID-19 pandemic

USA

60+

38%

67%

NR

60% live alone; 67% low-income; 3% veterans.

Kramer 2022 [37]

Identify whether Embodied Conversational Agents (ECA) could decrease loneliness in older adults

The Netherlands

73(5.33)

[65–85]

44%

NR

59% completed college or university

Mean(SD)[range]: eHealth literacy score 29.3(4.4) [15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34]; malnutrition risk 9.7(1.4) [7,8,9,10,11].