Table 1.
Characteristics of studies included in meta‐analysis and dose–response analysis
| Study (first author, year) | Participants [region] | Outcomes | Total score (percentage) | Quality |
|---|---|---|---|---|
| Myopia Incidence – Clinical Trial | ||||
| He et al. (2015) | 1903 schoolchildren; mean age: 6.61 years in the intervention group and 6.57 years in the control group; follow‐up for 3 years. [Guangzhou, China] | An additional 40‐min class of outdoor activities was added to each school day in the intervention group. Cumulative incidence of myopia: intervention group: 30.4%, control group: 39.5%; cumulative myopia progression: intervention group: −1.42 (−1.58 to −1.27) D, control group: −1.59 (−1.76 to −1.43) D. | 23 (92%) | High |
| Jin et al. (2015) | 391 schoolchildren; mean age: 10.77 years in the intervention group and 10.42 years in the control group; follow‐up for 1 year. [Shenyang, China] | An additional 40‐min class of outdoor activities was added to each school day in the intervention group. Incidence of myopia: intervention group: 3.7%, control group: 8.5%; myopia progression: intervention group: −0.10 ± 0.65 D, control group: −0.27 ± 0.52D. | 19 (76%) | High |
| Wu et al. (2013) | 571 schoolchildren; mean age: 8.89 years in the intervention group and 9.02 years in the control group; follow‐up for 1 year. [Taiwan] | Children were encouraged to go outside for outdoor activities during recess. Incidence of myopia: intervention group: 8.41%, control group: 17.65%; myopia progression: intervention group: −0.25 ± 0.68 D, control group: −0.38 ± 0.69D. | 15 (60%) | Medium |
| Yi & Li (2011) | 80 schoolchildren; mean age: 8.8 years in the intervention group and 8.9 years in the control group; follow‐up for 1 years. [Changsha, China] | Did near‐ and middle‐vision activities <30 hr/week and more outdoor activities than 14–15 hr/week. Annual myopia progression: intervention group: −0.38 ± 0.15D, control group: −0.52 ± 0.19D. | 15 (60%) | Medium |
| Myopia Incidence – Cohort Study | ||||
| French et al. (2013) | 863 schoolchildren in younger cohort; mean age: 6 years; follow‐up for an average of 6.1 years. | In both younger and older cohorts, there was a significant trend towards greater incident myopia in children who spent less time outdoors (younger cohort: low versus high: OR = 2.84, moderate versus high: OR = 1.14; older cohort: low versus high: OR = 2.15, moderate versus high: OR = 2.00) after adjusting for age, gender and parental myopia. | 11 (73.3%) | High |
| 1196 schoolchildren in older cohort; mean age: 12 years; follow‐up for an average of 4.6 years. [Sydney, Australia] | ||||
| Guggenheim et al. (2012) | 2005 schoolchildren; mean age: 11 years; follow‐up for an average of 4 years. [UK] | Time spent outdoors in age 8–9 years was predictive for incident myopia in age 11 years (OR = 0.65, 95% CI = 0.45 to 0.96). Adjusted for parental myopia, time reading, gender, physical activity/sedentary behaviour and constant. | 11 (73.3%) | High |
| Saw et al. (2006) | 994 schoolchildren; age: 7–9 years; follow‐up for an average of 3 years. [Singapore] | Outdoor activity was not associated with incident myopia (RR = 1.01, 95% CI = 0.98 to 1.04) in multivariate analyses. | 12 (80%) | High |
| Myopia Prevalence – Cross‐sectional Study | ||||
| Chua et al. (2015) | 572 children; age: 3 years. [Singapore] | Outdoor activity at 24 months was not associated with myopia in 3 years old (OR = 0.84, 95% CI = 0.61 to 1.17). | 11 (91.7%) | High |
| Zhou et al. (2015) | 1902 schoolchildren; mean age: 9.8 years. [Guangzhou, China] | More time outdoors was associated with less myopia (OR = 0.97, 95% CI = 0.95 to 0.99) in multilevel mixed‐effects logistic regression models of potential predictors of age, gender, total CSHQ score, night‐time sleep time and total time spent in near work. | 11 (91.7%) | High |
| Lee et al. (2015) | 5048 male military conscripts; age: 18–24 years. [Taiwan] | Engaging in fewer outdoor activities was significantly related to prevalence of myopia (OR = 0.94, 95% CI = 0.90 to 0.98) after adjusting for age, parental myopia, education level, reading distance, time spent reading, using computer, watching television and urbanization level. | 10 (83.3%) | High |
| Pan et al. (2015) | 4413 residents; age: 50 years or older. [Yunnan, China] | Less time spent outdoors per day in childhood was significantly associated with the presence of myopia (OR = 0.92, 95% CI = 0.84 to 0.98). | 12 (100%) | High |
| Guo et al. (2015) | 1565 schoolchildren; mean age: 11.9 years. [Inner Mongolia, China] | Presence of myopia was significantly associated with less hours spent outdoors after school (OR = 0.80, 95% CI = 0.64 to 0.99). | 9 (75%) | High |
| Zhou et al. (2014) | 823 schoolchildren; mean age: 9.21 years. [Lanzhou, China] | Outdoor activities was inversely associated with prevalence of myopia, although not statistically significant (OR = 0.937, 95% CI = 0.775 to 1.896) | 9 (75%) | High |
| Guo et al. (2013) | 681 primary students in rural and urban regions; mean age: 7.7 years. [Beijing, China] | Presence of myopia was associated with less time spent outdoors (OR = 0.32, 95% CI = 0.21 to 0.48) after adjusting for age and maternal myopia. | 10 (83.3%) | High |
| Low et al. (2010) | 3009 preschool children; age: 6–72 months. [Singapore] | Outdoor activity was not associated with preschool myopia (OR = 0.95, 95% CI = 0.85 to 1.07). Adjusted for familial clusters, age, gender, height, parental myopia and time spent reading words or pictures alone. | 10 (83.3%) | High |
| Deng et al. (2010) | 147 schoolchildren; age: 6–18 years. 89 | There was a statistically significant association between myopia and outdoor activities during the school year (OR = 0.915, 95% CI: 0.843 to 0.994) and the summer (OR = 1.00, 95% CI, 0.969 to 1.033), adjusting for age and number of myopic parents. | 8 (66.7%) | Medium |
| Dirani et al. (2009) | 1249 schoolchildren; mean age: 13.7 years. [Singapore] | Children who spent more time outdoors were 0.90 (95% CI = 0.84 to 0.96) times likely to have myopia, after adjusting for age, gender, ethnicity, school, books read per week, height and parental myopia, father's education level and IQ level. | 9 (75%) | High |
| Lu et al. (2009) | 998 schoolchildren; mean age: 14.6 years. [Xichang, China] | In logistic regression models of factors potentially predictive of myopia, outdoor activity was not significantly associated with myopia (OR = 1.14, 95% CI = 0.69 to 1.89). | 11 (91.7%) | High |
| Ip et al. (2008) | 2339 schoolchildren; mean age: 12 years. [Sydney, Australia] | Outdoor activity was significantly associated with myopia (OR = 0.97, 95% CI = 0.94 to 0.995). | 12 (100%) | High |
| Mutti et al. (2002) | 366 schoolchildren; mean age: 13.7 years. 89 | Myopes tended to spend less time engaged in sports activities (OR = 0.936, 95% CI = 0.892 to 0.983). Adjusted for parental myopia, dioptre‐hours per week, ITBS reading local and ITBS total language local. | 9 (75%) | High |
| Myopia Progression – Cohort Study | ||||
| Oner et al. (2015) | 50 myopic children; age: 9–14 years; follow‐up for 33.3 ± 10.3 (ranging from 17 to 55) months. [Turkey] | Outdoor activities had no correlation with annual myopia progression rate (r = −0.041, p = 0.766). | 10 (66.7%) | Medium |
| Li et al. (2015) | 2267 grade 7 students; age: 10 to 15 years; follow‐up for two years. [Anyang, China] | Outdoor activity was measured as a categorical variable and was not associated with change in SER (high versus low: β = 0.029 D/y, 95% CI = −0.015 to 0.072, p = 0.196). | 14 (93.3%) | High |
| Jones‐Jordan et al. (2012) | 835 myopic children who participated in CLEERE study; ages: ranging from 6 to 14 years; 1‐year progression interval. [USA] | An additional 10 hr of weekly outdoor activity was associated with 0.01 D progression per year (95% CI = −0.03 to 0.06), which was not statistically significant. | 12 (80%) | High |
| Jones et al. (2007) | 514 schoolchildren; mean age: 8.63 years; follow‐up for an average of 5 years. [USA] | The nonmyopic child participated in an average of 11.65 ± 6.97 hr/week of sports and outdoor activity, whereas the future myopic child participated in an average of 7.98 ± 6.54 hr/week (OR = 0.91, 95% CI = 0.87 to 0.95) after adjusting for parental myopia. | 13 (86.7%) | High |
| Saw et al. (2000) | 153 children; age: 6 to 12 years; mean follow‐up for 28 months. [Singapore] | No statistically significant associations between SER change and outdoor activities (hr/week) were observed (β: 0.013; 95% CI = −0.013 to 0.04; p: 0.33). | 10 (66.7%) | Medium |
OR = odds ratio, CI = confidence interval, RR = relative risk.