TABLE 1.
Studies investigating for causal association between body mass index/birthweight and asthma using MR
| First author, year | Method | Cases No. | Asthma risk measure | Atopic asthma and non‐atopic asthma | Quality score |
|---|---|---|---|---|---|
| Ha et al. (2021) 16 | Inverse‐variance weighted | 35,926 asthma cases and 227,924 controls of European | OR for adult onset moderate‐severe asthma: 1.12 (95% CI: 1.07–1.16), adult‐onset mild OR: 1.06 (1.03–1.08), childhood onset mild OR: 1.02 (0.99–1.05), childhood onset moderate to severe OR: 1.10 (1.04–1.17) | 13 | |
| Hyppönen et al. (2019) 25 | Two‐sample IVW | 325,404 white British individuals (UKB) | OR for asthma per SD (4.1 kg/m2) higher BMI 1.32 (95% CI 1.17–1.48) | 12 | |
| Xu et al. (2019) 24 | Two‐sample bi‐directional MR (Fixed effect meta‐analysis) | 322,154 of European ancestry | OR for asthma per unit (SD) increase in BMI 1.18 (95% CI: 1.11–1.25), p = 2*10−8. In UKB, BMI mean = 27.43 and SD = 4.785 | 12 | |
| Skaaby et al. (2018) 20 | One‐sample IV (2SLS) | 162,124 Europeans >16 years | OR for forever asthma per 1 kg/m2 increase in BMI: 1.07 (95% CI: 1.03–1.10). OR for hay fever per 1 kg/m2 increase in BMI 0.99 (95% CI: 0.96–1.01) | 12 | |
| Zeng et al. (2019) 27 | Two‐sample IVW MR | EGG GWAS consortium for birth weight (143,677 European) and GERA cohort for asthma (61,916 European) | OR for adult asthma per unit SD change of offspring birth weight 1.02 (95% CI: 0.84‐1.24) | 12 | |
| Au Yeung et al. (2021) 15 | Inverse‐variance weighted | 401,837 British of European ancestry (UKB) | OR for asthma per SD increase in childhood BMI 1.10 (95%CI: 0.99–1.22) and for adult BMI (per SD) 1.33 (95% CI: 1.25–1.43) | 11 | |
| Ҫolak et al. (2016) 55 | 85,437 Danish individuals >20 years | OR for any asthma per increase in BMI unit (1 kg/m2) 1.08 (95% CI: 0.98‐1.19) | 11 | ||
| Sun et al. (2020) 18 | Wald method | 56,105 Norwegians >20 years | OR for doctor‐diagnosed asthma per SD (4.1 kg/m2) increase in genetically determined BMI. Overall 1.49 (95% CI: 1.14–1.94), women 1.64 (1.17–2.30), men 1.31 (0.85–2.03) | OR per SD increase in genetically determined BMI forever asthma: 1.25 (0.89–1.77) and 1.42 (1.0–‐1.85) | 11 |
| Zhu et al. (2018) 22 | Generalized summary MR | 162,030 of European ancestry (GERA and UKB) | OR for asthma risk per SD (3.98 kg/m2) associated with BMI: 1.35 (95% CI: 1.20–1.51), and associated with height 0.90 (95% CI: 0.87–0.93). OR for allergic rhinitis associated with height 0.96 (95% CI: 0.92–0.99) | 10 | |
| Zhu et al. (2020) 21 | Summary data‐based MR | 457,690 of European ancestry (GIANT and UKB) | OR for late‐onset asthma after 16 years per SD increase in BMI (p‐value): 1.21 (p = 6.3 × 10−7) | OR for atopic asthma per SD increase in BMI: 1.20 (p = 0.04) and for non‐atopic: 1.10 (p = 8.4 × 10−6) | 9 |
| Chen et al. (2019) 17 | 2SLS regression | 5138 Taiwan children age 10‐11 | IV estimated RR for active asthma per unit z‐score for BMI overall: 1.04 (95% CI: 1.00–1.07). Males: 1.06 (95% CI: 1.01–1.12) and females: 1.02 (95% CI: 0.97–1.06) | 1.02 (1.00–1.04) and 1.03 (1.00–1.06) | 8 |
| Granell et al. (2014) 23 | Two‐stage GMM | 4835 UK children age 7 and 4298 children age 9 | RR for current asthma associated with BMI at 7 years 1.55 (95% CI: 1.16–2.07) and 9 years 1.38 (95% CI: 1.06–1.80) | For 7 years 0.98 (0.92–1.05) and 1.08 (1.02–1.14). For 9 years 0.96 (0.91–1.03) and 1.05 (0.99–1.11) | 8 |
| Chen et al. (2021) 26 | 2SLS method | 6130 Taiwan children | OR for active asthma at age 17 per unite increase in z‐score for BMI at birth weight 1.00 (95% CI: 0.82‐1.16) and at age 17: 1.08 (0.96‐1.22) | 7 |
Abbreviations: BMI, Body Mass Index; CI, Confidence interval; GERA, Genetic Epidemiology Research on adult health and aging; IV, Inverse variance; MR, Mendelian Randomization; OR, Odds ratio; RR, Relative Risk; SD, Standard deviation; 2SLS, Two stages Least Squares; Two‐stage GMM, Two‐stage Generalized moment method; UK, United Kingdom; UKB, United Kingdom Biobank.