Subgroup analyses according to possible factors that may modify the association between insomnia and asthma
| Characteristics of studies | Number of studies | OR with 95% CI | Heterogeneity (%) |
| Cohort studies6 7 21 29 32 | 5 | 1.73 (1.16 to 2.57) | 93.3 |
| Cross-sectional studies8–17 19 20 30 31 33–36 | 18 | 1.20 (1.14 to 1.28) | 54.9 |
| Insufficient sleep duration8 9 11 13–17 19–21 30 31 33 | 14 | 1.20 (1.13 to 1.28) | 56.1 |
| Poor sleep quality8–12 29 34 | 7 | 1.10 (1.05 to 1.16) | 0 |
| Adults6–8 14 17 20 31 33 34 36 | 10 | 1.36 (1.18 to 1.57) | 56.4 |
| Adolescents10 15 16 19 21 29 30 35 | 8 | 1.15 (1.08 to 1.21) | 59.8 |
| Children9 11 12 | 3 | 1.13 (0.97 to 1.32) | 14.7 |
| Studies conducted in Europe and America7 11 19–21 31 34 35 | 8 | 1.34 (1.21 to 1.48) | 22.2 |
| Studies conducted in Asia6 8–10 12–16 29 32 | 11 | 1.21 (1.12 to 1.31) | 79.8 |
| Studies in which BMI was adjusted7 9 13–16 20 21 30 33 34 | 11 | 1.22 (1.13 to 1.31) | 62.7 |
| 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) | 79.4 |
| Studies in which family history of asthma was adjusted12 21 | 2 | 1.16 (0.94 to 1.42) | 53.1 |
| 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) | 76.1 |
BMI, body mass index.