Type 1 diabetes and asthma: a systematic review and meta-analysis of observational studies

Type 1 diabetes (T1D) and asthma are both the top concurrent non-communicable diseases in the world, and the existence of a relationship between the two is an area of debate.

All eligible observational studies in PubMed and EMBASE databases from inception to August 2021 were searched for data extraction and analysis. The pooled odds ratio (OR) with corresponding 95% confidence intervals (95% CI) was evaluated using fixed-effects or random-effects models in RevMan 5.3, and I² and Cochran Q tests were used to assess the heterogeneity.

22 studies with 25,578 T1D and 3,330,901 non-T1D were included in this meta-analysis. After data analysis, there seems to be no apparent connectivity between asthma and T1D as the crude OR (cOR) was 1.07 (95%CI, 0.93-1.23). Nevertheless, after limiting the meta-analysis to 6 studies with adjusted OR (aOR) available, the results suggested a positive association between T1D and asthma (aOR, 1.15; 95%CI, 1.06-1.25). Corresponding with this, a meta-analysis of cohort studies also found a positive association between T1D and asthma with the pooled cOR of 1.27 (95% CI, 1.09-1.49) and aOR of 1.15 (95%CI, 1.05-1.26). Further analysis of 7 studies in which the diagnosis of asthma precedes T1D onset revealed that asthma patients are at increased risk of subsequent T1D with the pooled cOR of 1.23 (95%CI, 1.04-1.44) and aOR of 1.58 (95% CI, 1.11-2.24).

Our meta-analysis suggests a possible association between T1D and asthma, and patients who were previously diagnosed with asthma carried higher odds of developing T1D.