Characteristics of included studies
| Author | Region | Study design | Age | Gender, male (%) | Diagnosis of asthma | Exposure | Measure of exposure | OR with 95% CI | Adjusted covariates |
| Brumpton et al7 | Norway | Prospective cohort study | 20–65 years | 55.7 | Questionnaire about physician diagnosis and prescription of asthma drugs | Insomnia | Questionnaire | 2.67 (1.15 to 5.45) | Age, gender, BMI, education, economics, smoking, anxiety and depression |
| Han et al15 | Korea | Cross-sectional study | 12–18 years | 50.2 | Questionnaire about physician diagnosis | Insufficient sleep | Questionnaire | ˂ 5 hours, 1.09 (1.04 to 1.14); 6 hours, 1.05 (1.00 to 1.10) | Age, gender, BMI, smoking, alcohol use, regular physical activity, economics, residence, school type, sexual experience, drug use, academic achievement, family structure, stress, health status, happiness, depression, suicidal idea, suicidal plan and suicidal attempt |
| Bakour et al19 | The United States | Cross-sectional study | High school students | 50.3 | Questionnaire about physician diagnosis | Insufficient sleep | Questionnaire | 1.22 (1.07 to 1.40) | Age, gender, race, smoking, alcohol use, marijuana use, physical activity |
| Bakour et al21 | The United States | Longitudinal cohort study | 12–18 years | 50.1 | Questionnaire about physician diagnosis | Insufficient sleep | Questionnaire | 1.52 (1.11 to 2.10) | Age, gender, race, BMI, smoking, alcohol, physical activity, parental income, parental education, pubertal development, family history of asthma |
| Björnsdóttir et al33 | Multicenter | Cross-sectional study | 39–67 years | 52.3 | Questionnaire about physician diagnosis | Insufficient sleep | Questionnaire | 0.97 (0.62 to 1.52) | Gender, age, marital status, exercise, smoking, BMI |
| Dashti et al20 | The United States | Cross-sectional study | ≥ 18 years | 57.6 | Medical record | Insufficient sleep | Questionnaire | 1.23 (1.09 to 1.38) | Age, gender, race, BMI |
| Dai et al31 | The United States | Cross-sectional study | ≥ 18 years | 43.6 | Medical record | Insufficient sleep | Questionnaire | ˂ 5 hours, 1.7 (1.1 to 2.4); 6 hours, 1.2 (0.8 to 1.7) | Gender, age, race, education, economics, employment status, depression |
| Choi et al14 | Korea | Cross-sectional study | 19–39 years | 41.8 | Questionnaire about physician diagnosis | Insufficient sleep | Questionnaire | ˂ 5 hours, male, 1.265 (0.79 to 2.206); ˂ 5 hours, female, 1.553 (1.023 to 2.359); 6 hours, male, 1.299 (0.959 to 1.759); 6 hours, female, 1.06 (0.757 to 1.484) | Age, BMI, smoking, alcohol use, physical activity, economics, serum 25(OH)D level, stress level |
| Zhang et al6 | Hong Kong, China | Prospective cohort study | Adults, 40.7±5.4 (mean±SD) | 46.5 | Questionnaire about physician diagnosis | Insomnia syndrome | Questionnaire | 17.9 (2.28 to 140) | Age, gender, education, economics, drug use |
| Nutakor et al17 | Multicenter | Cross-sectional study | ≥ 50 years | 53.5 | Internet interview | Insufficient sleep | Internet interview | 1.34 (0.75 to 2.40) | Gender, residence, age, marital status, education, economics |
| Stangenes et al11 | Norway | Cross-sectional study | ˂ 11 years | NA | Questionnaire about physician diagnosis and prescription of asthma drugs | Poor sleep quality and insufficient sleep | Questionnaire | Poor sleep quality, 1.1 (0.5 to 2.5); insufficient sleep, 2.6 (0.9 to 7.6) | Gender, single parenthood, maternal education |
| Seow et al8 | Singapore | Cross-sectional study | ≥ 18 years | 49.6 | Questionnaire about physician diagnosis | Poor sleep quality and insufficient sleep | Questionnaire | Poor sleep quality, 1.011 (0.784 to 1.304); insufficient sleep, 1.174 (0.899 to 1.534) | Sociodemographic and lifestyle factors, physical and mental disorder |
| Blank et al35 | The United States | Cross-sectional study | 13–18 years | 48.6 | Face-to-face interview | Insomnia | Face-to-face interview | 1.53 (1.19 to 1.96) | Age, gender, race |
| Lim et al16 | Korea | Cross-sectional study | 12–18 years | 51.6 | Questionnaire about physician diagnosis | Insufficient sleep | Questionnaire | ˂ 6 hours, 1.38 (1.15 to 1.65); 6 to 7 hour, 1.07 (0.9 to 1.27) | Age, genders, region, economics, smoking, physical activity, sitting time, obesity |
| Estanislau et al30 | Brazil | Cross-sectional study | 12–17 years | 43.8 | Questionnaire about physician diagnosis | Insufficient sleep | Questionnaire | 1.17 (1.01 to 1.35) | Age, gender, type of school, mental disorders, excess weight |
| Gureje et al36 | Nigeria | Cross-sectional study | ≥ 65 years | 46.2 | Face-to-face interview | Insomnia | Face-to face interview | 2.1 (1.4 to 3.1) | Age, gender |
| Basnet et al34 | Finland | Cross-sectional study | 25–74 years | 47.3 | Questionnaire about physician diagnosis | Poor sleep quality | Questionnaire | 1.435 (0.96 to 2.14) | Age, gender, living status, education, region, smoking, alcohol intake, physical activity, BMI |
| Ma et al9 | China | Cross-sectional study | 3–6 years | 51.7 | Questionnaire about physician diagnosis | Insufficient sleep and difficulty maintaining sleep | Questionnaire | Insufficient sleep, 0.95 (0.49 to 1.84); difficulty maintaining sleep, 1.49 (1.05 to 2.13) | Age, gender, region, maternal education, BMI, delivery mode, birth weight, maternal tobacco exposure during pregnancy, feeding pattern before 6 months |
| Chen et al10 | China | Cross-sectional study | 12–18 years | 64.4 | Questionnaire about physician diagnosis | Poor sleep quality | Questionnaire | Difficulty falling asleep, 1.00 (0.77 to 1.31); difficulty maintaining sleep, 1.25 (0.94 to 1.67) | Demographic characteristics, family structure, gestation, delivery, feeding, socioeconomic status, health problems, daily activity and behaviour routine |
| Lin et al32 | Taiwan, China | Prospective cohort study | All ages | 40.0 | Medical record | Insomnia | Medical record | 1.89 (1.64 to 2.17) | Age, gender, comorbidity, region, economics |
| Chen et al29 | Taiwan, China | Prospective cohort study | 12–17 years | 51.2 | Questionnaire about physician diagnosis | Poor sleep quality | Questionnaire | 1.10 (1.03 to 1.17) | Age, sex, parental education, economics |
| Chen et al12 | China | Cross-sectional study | ≤2 years | 51.1 | Medical record | Poor sleep quality | Face-to-face interview | Difficulty falling asleep, 1.05 (0.89 to 1.24); difficulty maintaining sleep, 1.06 (0.81 to 1.39) | Gender, maternal age, maternal education level, economics, family history of allergy, delivery mode, household secondhand smoke |
| Hu et al13 | China | Cross-sectional study | All ages | 46.5 | Questionnaire about physician diagnosis | Insufficient sleep | Questionnaire | 1.72 (1.32 to 2.24) | Gender, age, smoking, alcohol, region, BMI |
.BMI, body mass index; NA, not applicable.