Table 1.
Descriptive characteristics of included studies.
| Lead Author (Year) | Location | N | Age/Grade at Baseline (Mean ± SD or Range) | Gender | Setting | Follow-Up Length | Measure of Outdoor Time |
|---|---|---|---|---|---|---|---|
| Studies Beginning in Early Childhood (<5 Years) | |||||||
| Arcury (2017) [34] | United States (North Carolina) | 221 | 2–3 years | 52% girls | Community | 2 years | Parent-reported. 24 h recall: number of minutes child spent (1) at playground and (2) in the yard |
| Cameron (2019) [35] | Australia (Melbourne) | 307 | 3.61 years (range: 3.2–4.5) | Not stated | Cohort | 2 years | Parent-reported OT on an average day in last week |
| Davison (2011) [36] | United States (New York State) | 1322 | 2–5 years | 51.0% girls | Women and children clinics | 1 year | Parent-reported OT (dichotomized as ≥60 min/day vs. less) |
| Essery (2008) [37] | United States (Texas) | 90 | 3.1 ± 1.1 years | 53% girls | Home | 3 months | Parent-reported. Time spent in OP per day |
| Händel (2017) [38] | Denmark (Copenhagen) | 307 | 4 years (median) | 42.2% girls | Municipality (birth registry) | 15 months | Parent-reported OP in min/week |
| Hesketh (2015) [39] | Australia (Melbourne) | 542 | 3.9 ± 1.5 months | 47.4% girls | Maternal and Child Health service | 16 months | Parent-reported OT per day |
| Hnatiuk (2013) [40] | Australia (Melbourne) | 206 | 3.5 ± 1 months | 46.6% girls | First-time parent groups | 5 months | Parent-reported OT in min/week |
| Honda-Barros (2019) [41] | Brazil (Recife, Pernambuco) | 700 | 3–5 years | 47.9% girls | Schools | 2 years | Standardized interview (parent-reported OP in min/day) |
| Huang (2021) [42] | China (Longhua) | 26,611 | 1 year | 45.7% girls | Schools | 2 years | Parent-reported frequency and duration of OT |
| Li (2022) [43] | China (Changsha) | 953 | 12 months | 48.4% girls | Clinics/hospitals | 4 years | Parent-reported OT (hours/day) |
| Lumeng (2017) [44] | United States (Michigan) | 697 | 4.1 ± 0.5 years | 51% girls | Head Start programs (preschool) | 7 months | Parent-reported OT on weekdays and weekend days |
| Sääkslahti (2004) [45] | Finland (Turku) | 228 | Intervention: 4.6 ± 0.5 years; control: 4.4 ± 0.4 | 48.2% girls | Clinic | 3.5 years | Parent-reported. Diary reporting time spent in OP (hours/weekend) |
| Shah (2017) [46] | United Kingdom (Avon) | 2833 | 2 years | 50.2% girls | Cohort | 13 years (6.5 years for OT) | Parent-reported OT per day |
| Tandon (2019) [47] | United States (Seattle, Washington) | 82 | Active play group: 4.5 ± 0.6 years; outdoor play group: 4.6 ± 0.4 | 56.1% girls | Preschools | 12 weeks | Direct observation of outdoor activities (child-initiated and teacher-initiated) |
| Thiering (2016) [48] | Germany | 837 | Birth | 49% girls | Birth cohorts | 15 years | Child-reported OT: h/day |
| Xu (2016) [49] | Australia (Sydney) | 369 | 2 years | 50% girls | Birth cohort | 3 years | Mother-reported. Hours of OP per weekday and weekend day |
| Studies beginning in childhood (5–11 years) | |||||||
| Avol (1998) [50] | United States (Southern California) | 195 | 10–12 years | 48.7% girls | Cohort (hospital) | Mid-spring–late summer (~4–5 months) | Child-reported (diary). Location recorded hourly for four days |
| Bacha (2010) [51] | United States (10 sites) | 868 | Grade 3 | 50.8% girls | Birth cohort | 2 years (for main exposure) | Child-reported OT in the neighbourhood on weekdays between school dismissal and 6 pm (dichotomized as any vs. none) |
| Bagordo (2017) [52] | Italy (5 towns) | 1164 | 6–8 years | 49.1% girls | Schools | ~5 months (winter 2014–2015 to late spring 2015) | Parent-reported OP for >1 h per day (yes/no) |
| Buller (2020) [53] | United States (California) | 1758 | 8.16 ± 2.04 years | 49.1% girls | Schools | 20 months a | Parent-reported. OT between 10 am and 4 pm during the week (none, 30 min or less, or 31 min or more) |
| Christiana (2017) [54] | United States (Western North Carolina) | 70 | 5–13 years | 44.3% girls | Pediatric clinics | 3 months | Parent-reported frequency of OT |
| Cleland (2008) [55] | Australia (Melbourne) | 548 | Two cohorts: 5–6 years and 10–12 years | 53% girls | Schools | 3 years | Parent-reported OT on weekdays and weekend days for warmer and cooler months |
| Cleland (2010) [56] | Australia (Melbourne) | 421 | Two cohorts: 5–6 years and 10–12 years | 51.5% girls | Schools | 5 years | Parent-reported OT on weekdays and weekend days for warmer and cooler months |
| Cortinez-O’Ryan (2017) [57] | Chile (Santiago) | 100 | 4–12 years | 51% girls | Neighbourhood | 12 weeks | Parent-reported frequency and duration of OP |
| Flynn (2017) [58] | United States (Southeast region) | 27 | 10.7 ± 3.3 years | 51.9% girls | Neighbourhoods | 4 weeks | Parent-reported. Total minutes of outdoor PA/week |
| Ford (2002) [59] | United States (Atlanta, Georgia) | 28 | 7–12 years | 53.4% girls | Community clinic | 4 weeks | Parents and children reported together: typical amount of OT per day |
| Gerards (2015) [60] | Netherlands (Limburg) | 56 | 7.2 ± 1.4 years | 55.8% girls | Public health services | 12 months | Parent-reported. Days per week and number of hours playing outside |
| Handy (2008) [61] | United States (Northern California) | 272 | <16 years | Not stated | Neighbourhoods | 1 year (retrospective) | Parent-reported. Frequency of OP in previous week |
| He (2015) [12] | China (Guangzhou) | 1848 | 6–7 years | 46% girls | Schools | 3 years | Parent-reported OT in min/day |
| Kemp (2022) [62] | Australia (national) | 2971 | 10.4 ± 0.5 years | 49.2% girls | Home | 2 years | Child-reported time-use diaries with a category for non-organized outdoor/nature PA in min/day |
| Li (2021) [63] | Canada (Toronto) | 265 | 5.5 ± 2.5 years | 47.5% girls | Clinics/hospitals | 3 months | Parent-reported OT (hours and min/day) |
| Milne (2000) [64] | Australia (Perth) | 1386 | 5–6 years | 48% girls | Schools | 17 months | Parent-reported. Average time each day that the children were outdoors between 8 am and 4 pm and between 11 am and 2 pm |
| Milne (2007) [65] | Australia (Perth) | 1116 | 5–6 years | 49.8% girls | Schools | 4 years | Parent-reported. Average time each day that the children were outdoors between 8 and 11 AM, between 11 AM and 2 PM, and between 2 and 5 PM |
| Nigg (2021) [66] | Germany | 570 | 5.3 ± 0.8 years | 54.7% girls | Community | 11 years | Participant-reported OP frequency in a typical week (from 0 to 7 days) |
| Ngo (2009) [67] | Singapore | 285 | 6–12 years | 45.9% girls | Program/community | 9 months | Parent-reported OT on weekdays and weekend days (questionnaire and diary) |
| Nordvall-Lassen (2018) [68] | Denmark (Aarhus) | 4941 | 9–11 years | 49.6% girls | Birth cohort | 9–11 years | Parent-reported OT (h/week) |
| Ostrin (2018) [69] | United States (Houston, Texas) | 60 | 7.6 ± 1.8 years | 40% girls | Cohort | 1 year | Parent-reported OT and Actiwatch-measured ambient light exposure |
| Remmers (2014a) [70] | Southern Netherlands | 1317 | 5.0 ± 0.5 years | 49% girls | Cohort | 2 years | Parent-reported OP. Frequency and duration in an average week for the last 4 weeks |
| Remmers (2014b) [71] | Netherlands | 2007 | 5.75 ± 0.42 years | 49.5% girls | Healthcare cohort | 2 years | Parent-reported. Total duration of unstructured OP in an average week |
| Sadeh-Sharvit (2020) [72] | United States | 7 | 5.95 ± 3.57 years | Not available | Hospital | 8 weeks | Parent-reported. OP checklist |
| Sanchez-Tocino (2019) [73] | Spain (Valladolid and Burgos, Castilla y León) | 82 | 10 ± 3 years | 52.4% girls | Hospitals | 1.5 years | Parent-reported OT. Hours/week |
| Schneor (2021) [74] | Israel (central) | 19 | 10.2 ± 0.9 years | 0% girls | Clinics | 21 months | Actiwatch-measured ambient light exposure |
| Shepherd-Banigan (2014) [75] | United States (Eastern Washington State) | 99 | 6–12 years (median: 9.5) | 48% girls | Farming setting | 9 months | Parent-reported. Daily diary reporting children’s OT |
| Sum (2022) [76] | Singapore | 604 | 7.1 ± 3.6 years | 50.8% girls | Clinics | 3–5 months (retrospective) | Parent-reported frequency of OP or exercise |
| Van Griecken (2014) [77] | Netherlands | 293 | 5.8 ± 0.4 years | 61.9% girls | Healthcare centres | 2 years | Parent-reported (dichotomized as playing outside <1 h vs. ≥1 h per day) |
| Van Stralen (2012) [78] | Netherlands (Amsterdam) | 600 | 9.8 ± 0.7 years | 51% girls | Schools | 20 months | Child-reported frequency of OP |
| Walker (2021) [79] | United States (Texas) | 13 | 5–10 years | 46% girls | University (OP room) | 8 weeks | Parent-reported OT (hours/day) on weekdays and weekend days |
| Wolters (2022) [80] | Belgium, Cyprus, Estonia, Germany, Hungary, Italy, Spain, and Sweden | 2094 | 6.2 ± 1.8 years | 49% girls | School | 6 years | Child- or parent-reported OT (hours/day) for weekdays and weekend days |
| Studies beginning in adolescence (12–17 years) | |||||||
| Dunton (2007) [81] | United States (Southern California) | 524 | 14.5 ± 0.5 years | 49% girls | Schools | 4 years | Electronic ecological momentary assessment: proportion of entries in outdoor context |
| Evenson (2018) [82] | United States (California and Minnesota) | 265 | Grades 10–11 | 100% girls | Parks | 1 year | GPS-measured. Minimum park visit duration of 3 min to count as time spent in parks |
| French (2013) [83] | Australia (Sydney) | 1739 | 6.7 (younger cohort) and 12.7 (older cohort) | 47.3% girls | Cohort | 5–6 years | Parent-reported (and child-reported if 12+ years old). Sum of weekly time spent in outdoor leisure and sport |
| Gopinath (2013) [84] | Australia (Sydney) | 752 | 12.7 years at baseline | 53.3% girls | Cohort | 5 years | Sum of youth-reported time spent in different outdoor sporting activities in an average week |
| Lin (2017) [85] | China (Beijing) | 217 | 8.4 ± 1.1 and 14.2 ± 1.7 years for the primary and secondary students | 51.2% girls | Clinics | 3 years | Child-reported (parental help if needed). Sum of hours spent in outdoor sports and leisure after school |
| Miller (2017) [86] | United States (Chicago, Illinois) | 250 | Mean age of 12 years | 59% girls | Neighbourhoods | 1 year | Child-reported (ecological momentary assessment). Location reported ~7 times throughout the day. |
| Watowicz (2012) [87] | United States (Midwest) | 135 | 12.8 ± 2.8 years | 60% girls | Hospital (patients of a pediatric weight management centre) | 45 months (range = 8 to 86 months) [retrospective] | Children and parents completed questionnaire together (OP dichotomized as <1 vs. ≥1 h/day) |
Note: N = Sample size (only participants with outdoor time data were included); OP = outdoor play; OT = outdoor time; PA = physical activity; SD = standard deviation. a For the Buller et al. [33] study, the time period between pretest and post-test was not clear, but the intervention lasted 20 months.