Table 3.

Study characteristics.

Study	Intervention name	Section A (1) Population characteristics (CYP)	Significant differences at baseline	Section A (2) Population characteristics (OP)	Significant differences at baseline	Who have outcomes been reported for?	Country	Section C—Outcomes (OP)
Carcavilla (2020)	Smile Connect	Age INT M 16.2 years (SD 0.97) CON M 16.3 years (SD 0.48) Recruitment setting secondary school in Italy Total number recruited n = 48 (24 per group) Gender Female 100% Ethnicity Italian (otherwise not reported)	None	Age INT Mean 83.8 years (SD 7.89) CON Mean 81.5 years (SD 10.9) Recruitment setting place of residence (care home) Place of residence one of three residential care homes in Spain Total number recruited n = 46 (CON 25, INT 21) Gender INT 70% Female CON 52% Female Ethnicity Spanish (otherwise not reported)	None for age, education or cognitive capacity	Children and/or young people Older people	Italy Spain	Self esteem Mental Health
Cardona (2002)	None—Task orientated intergenerational program	Age Mean 16.67 (SD 0.56) Recruitment setting school Total number recruited n = 3 Gender Female 66.6% (n = 2) Male 33.3% (n = 1) Ethnicity not described	Not reported	Age 67–92 range INT Mean 87.57 (SD 3.95) CON Mean 80.83 (SD 8.77) Recruitment setting assisted living facility Place of residence assisted living facility Total number recruited n = 13 Gender 4 Male 9 Female Ethnicity not described	Not reported	Children and/or young people intended to be both but only ended up with 3 younger people Older people	USA	Depression Self‐esteem
Chippendale (2015)	Living Legends	Age not reported but in tertiary education 18+ Recruitment setting not reported Total number recruited n = 24 students (6 at each site) Gender not described Ethnicity not reported	Not reported	Age CON mean 75.81 years (SD 10.86) INT mean 77.85 years (SD 8.55) Recruitment setting—four community based older adult programme sites in New York City Place of residence living in their own apartment Total number recruited n = 47 (data only from 39), from four sites 3 were retirement community programs and 1 was a senior centre. Gender CON Male n = 1 (5.9%) Female n = 15 (93.8%) INT Male n = 3 (13%) Female n = 20 (87%) Ethnicity White 57.5% African American 36% Middle Eastern 12.5%	None	Older people	USA	Agency MLQ‐Presence Scores
Dawson (2017)	Ageless Play	Age Not reported but range is 6–11 years Recruitment setting school Total number recruited Not reported (matched pairs for the OP so 17?) Gender not described Ethnicity not reported	Not reported	Age Mean age 71 years (SD 8.15), range 55–84 years Recruitment setting Word of mouth, flyers, letter and emails in the surrounding community of the senior centre Total number recruited n = 17 (2 removed from analysis) Place of residence Not reported Gender Female 60% Male 40% Ethnicity White (73%), 20% Black/African American (20%) Other (6%)	Significant difference between groups for education only	Older people	USA
Detmer (2020)	None (Intergenerational music therapy)	Age 3–4years Recruitment setting University based child care setting Total number recruited n = 32 (16 in each group) Gender not described Ethnicity not reported	Not reported	Age 72–98 years Recruitment setting Senior living facility (some personal care unit and some memory care unit) Total number recruited n = 15 Place of residence senior living facility (some personal care unit and some memory care unit) Gender not described Ethnicity not reported	Not reported	Children and/or young people Older people	USA
George (2011)	None (Intergenerational Volunteering)	Age 5–6 years and 11–14 years (range 5–14 years) Recruitment setting place of education (The Intergenerational School—TIS) Total number recruited n = 32 (two classes of 16) Gender not described Ethnicity not reported	Not reported	Age INT = Mean 85.7 years (SD 5.97) CON = Mean 81.4 years (SD 8.2) Recruitment setting Place of residence—assisted living facility Total number recruited n = 15 Place of residence Assisted living facility Gender INT 7 Female 1 Male CON 6 Female 1 male Ethnicity not reported	None	Older people	USA
Giglio (2006)	None	Age 3–4 years Recruitment setting Pre‐school classroom from the day care centre in the shared site facility Total number recruited n = 17 Gender Female n = 5 Male n = 12 Ethnicity not reported	Not reported	Age 70–97 years Mean 83.10 (SD 5.75) Recruitment setting Place of residence—memory care centre in a nursing home Total number recruited n = 29 Place of residence continuous care facility—includes retirement living, assisted living, skilled nursing and memory care services. This population were from the memory care centre which houses those with Alzheimers or dementia Gender Ethnicity not reported	Not reported	Older people	USA
Gruenewald (2016)	Experience Corps	Age Not reported—elementary schools Recruitment setting 6 schools Total number recruited Not reported Gender not described Ethnicity not reported	Not reported	Age 60–89 years Mean 67.4 years (SD 5.9) Recruitment setting Community health fairs, senior centres and housing, life care communities, churches, and community organisations; mailings to members of clubs, AARP, and other retiree organisations, senior housing facilities, and senior centres; and targeted radio stations, including public service announcements and advertising Total number recruited n = 702 (INT 352, CON 350) Place of residence Not reported Gender Female 85% Ethnicity 92% Black/African American 5% White/Caucasian 3% other	Not reported	Older people	USA
Low (2015)	Grandfriends	Age All 4 years old Recruitment setting Preschool class of a childcare centre Total number recruited n = 21 Gender Female 48% (n = 10) Male 52% (n = 11) Ethnicity not reported	Not reported	Age Mean 91 years Recruitment setting place of residence (aged care facility) Total number recruited n = 40 Place of residence Three aged care facilities Gender Female 80% (n = 32) Male 20% (n = 8) Ethnicity not reported	None	Children and/or young people Older people	Australia
Rook (2003)	Foster Grandparent program	Age Not described Recruitment setting Place of residence (state hospital) Total number recruited Not reported but presumably one for each OP in the intervention group Gender not described Ethnicity not reported	Not reported	Age 60–92 years Mean 70.52 Recruitment setting Community group through mailings and phone calls to older people chosen randomly but based on age and economic stratification Total number recruited n = 180 (52 INT 59 CON) Place of residence own home Gender Female 65.6% Ethnicity Caucasian 90% Non Caucasian 10%	Some significant differences across 3 study groups including age, chronic health problems, non‐White participants and SES	Older people	USA
Sakurai (2018)	REPRINTS	Age Not described but children from six elementary schools, three kindergardens and six public child care centres Recruitment setting school, kindergarten and public child care centres Total number recruited Not reported Gender not described Ethnicity not reported	Not reported	Age Overall Mean 68.0 (SD 4.9) Recruitment setting Recruited from people involved in the REPRINTS study Total number recruited n = 177 (only 59 completed all assessments at 6 years) Place of residence Own home Gender Female 85% Ethnicity not reported	Only significant difference in number of years of education	Older people	Japan
Shkilnyk (1984)	None (type of visiting programme)	Age Mean 12.47 years (Grade 6–8) Recruitment setting school Total number recruited n = 72 Gender not described Ethnicity not reported	Not reported	Age Mean 84.57 years Recruitment setting Nursing care home Total number recruited n = 54 Place of residence care home Gender not reported Ethnicity not reported	Not reported	Children and/or young people Older people	Canada
Sipsas‐Herrmann (2000)	SCARE (Student Created Aggression Replacement Education)	Age 11–12 years Recruitment setting School Total number recruited n = 194 (172 remained after attrition) Gender Female 102 (92 remained) Male 92 (80 remained) Ethnicity 80% anglo 15% Hispanic 5% other	Not reported	Age INT 60–81 years CON 60–92 years Recruitment setting community and senior centre Total number recruited INT 36 CON 37 (18 assigned to the control group and 18 to the SCARE program plus 37 retired senior citizen volunteers (14 male, 23 female) ages 60 to 92, not actively participating in the project were recruited as non‐trainers for the control condition portion of the cross‐generational investigation) Place of residence own home Gender INT 10 Male 26 Female CON 14 Male 23 Female Ethnicity not reported	Not reported	Children and/or young people Older people	USA
Thornton (2018)	Senior Change makers	Age Mean 24 years (SD 7.53) college students Recruitment setting University through word of mouth, email lists sent to local university students in health‐related fields of study Total number recruited n = 21 Gender Female 81% Male 19% Ethnicity 33% White non‐Hispanic	None	Age Mean 75 (SD 9) years Recruitment setting Place of residence (senior housing residence) Total number recruited n = 60 Place of residence Senior housing residence Gender Female 84% Male 16% Ethnicity White non‐Hispanic 70% Hispanic 10% African American 11% American Indian 7% Asian 5%	None	Children and/or young people Older people	USA