Quality of evidence for overall and subgroup analyses
| Overall and subgroup analyses | Number of studies | OR | 95% CI | Quality of evidence |
| Overall6–17 19–21 29–36 | 23 | 1.38 | 1.10 to 1.74 | ⨁〇〇〇 Very Low |
| Cohort studies6 7 21 29 32 | 5 | 1.73 | 1.16 to 2.57 | ⨁〇〇〇 Very Low |
| Cross-sectional studies8–17 19 20 30 31 33–36 | 18 | 1.20 | 1.14 to 1.28 | ⨁〇〇〇 Very Low |
| Insufficient sleep duration8 9 11 13–17 19–21 30 31 33 | 14 | 1.20 | 1.13 to 1.28 | ⨁〇〇〇 Very Low |
| Poor sleep quality8–12 29 34 | 7 | 1.10 | 1.05 to 1.16 | ⨁⨁〇〇 Low |
| Adults6–8 14 17 20 31 33 34 36 | 10 | 1.36 | 1.18 to 1.57 | ⨁〇〇〇 Very Low |
| Adolescents10 15 16 19 21 29 30 35 | 8 | 1.15 | 1.08 to 1.21 | ⨁〇〇〇 Very Low |
| Children9 11 12 | 3 | 1.13 | 0.97 to 1.32 | ⨁〇〇〇 Very Low |
| Studies conducted in Europe and America7 11 19–21 31 34 35 | 8 | 1.34 | 1.21 to 1.48 | ⨁⨁〇〇 Low |
| Studies conducted in Asia6 8–10 12–16 29 32 | 11 | 1.21 | 1.12 to 1.31 | ⨁〇〇〇 Very Low |
| Studies in which BMI was adjusted7 9 13–16 20 21 30 33 34 | 11 | 1.22 | 1.13 to 1.31 | ⨁〇〇〇 Very Low |
| Studies in which BMI was not adjusted6 8 10–12 17 19 29 31 32 35 36 | 12 | 1.29 | 1.14 to 1.47 | ⨁〇〇〇 Very Low |
| Studies in which family history of asthma was adjusted12 21 | 2 | 1.16 | 0.94 to 1.42 | 〇〇〇〇 Very Low |
| Studies in which family history of asthma was not adjusted6–11 13–17 19 20 29–36 | 21 | 1.27 | 1.18 to 1.36 | ⨁〇〇〇 Very Low |
BMI, body mass index.