Meta-analysis
Two cohort studies reported HR as the measure for the risk of T1DM in asthmatic patients. There was significant heterogeneity (I ² = 90.2%, P = 0.001). In random-effects model analysis, pooled HR for the risk of T1DM was 1.30 (95% CI 1.05–1.61, P =0.014). Figure 2 shows the forest plot of the included studies.
Three studies reported HR as the measure for asthma risk in T1DM patients. There was significant heterogeneity (I ² = 92.7%,P < 0.001). In random-effects model analysis, pooled HR was 0.98 (95% CI 0.64–1.51,P =0.941). In the meta-analysis of the 12 studies that reported OR as the measure for asthma risk in T1DM patients, pooled OR was 0.84, 95% CI 0.65–1.08, P =0.168). Figure 3 shows the forest plot of the included studies. Subgroup analysis indicated that geographical location and quality grade could not explain the heterogeneity (Table S4). In meta-regression analysis, the observed heterogeneity could not be explained by the year of publication, region, incidence of asthma in the control group, sample size and quality score (Table S5). Sensitivity analysis failed to show significant bias caused by any single study (Figure S1). Funnel plots indicated some degree of publication bias (Figure S2), but Begg’s test did not confirm the bias (P of =0.82).