Influence of the TH1/TH2 Paradigm: The Prevalence of Asthma and Allergic Diseases in Patients with Type 1 Diabetes in the United States

Prevalence of asthma in people with type 1 diabetes mellitus: a scoping review

BACKGROUND

According to the Th1/Th2 paradigm, the expansion of Th1-type clones in individuals with type 1 diabetes results in reduced Th2-type clones, preventing the development of atopic diseases and vice versa. However, there is no consensus regarding the direct or inverse relationship between autoimmune and atopic diseases.

OBJECTIVE

The aim of this scoping review was to examine the knowledge gap about the possibility of coexistence of asthma and type 1 diabetes and determine the prevalence of this association.

METHODS

A scoping review was conducted, following the proposal of the Joanna Briggs Institute. The Population, Concept, and Context strategy was used to formulate the guiding question. The proposed question was: "What is the prevalence of asthma in people with T1DM?" After excluding duplicate articles, analyzing titles and abstracts, and excluding articles that did not answer the guiding question, 17 articles remained and were included in this review.

RESULTS

Most of the articles selected conformed to the Th1/Th2 hypothesis, as the prevalence of asthma was lower in individuals with T1DM. However, similar or higher prevalence of asthma was found between cases and controls in few articles.

CONCLUSION

The prevalence of asthma in people with T1DM ranged from 1.7% to 23.1%. Maybe the mechanisms that characterizes the Th1/Th2 paradigm aren't as simple as just the interaction of certain cytokines, since Th1-mediated autoimmune diseases and Th2- mediated atopy can coexist.

Childhood asthma and type 1 diabetes mellitus: A meta-analysis and bidirectional Mendelian randomization study

BACKGROUND

Worldwide incidence and prevalence of both asthma and type 1 diabetes mellitus (T1DM) in children have been increasing in past decades. Association between the two diseases has been found in some but not in other studies.

OBJECTIVE

We conducted a meta-analysis to verify such an association, and bidirectional Mendelian randomization analysis to examine the potential cause-effect relationships.

METHODS

Three databases (PubMed, Embase, and Web of Science) were searched from their inception to February 1, 2021. Pooled hazard ratios (HR) or odds ratios (OR), and 95% confidence intervals, were calculated. Associations between single-nucleotide polymorphisms with childhood asthma and T1DM were selected based on genome-wide association studies. The outcome datasets were obtained from FinnGen study. We used the inverse-variance-weighted (IVW), weighted median and MR-Egger methods to estimate causal effects. To assess robustness and horizontal pleiotropy, MR-Egger regression and MR pleiotropy residual sum and outlier test were conducted.

RESULTS

In meta-analysis, childhood asthma was associated with an increased risk of T1DM (HR = 1.30, 95% CI 1.05-1.61, P = .014), whereas T1DM was not associated with the risk of asthma (HR = 0.98, 95% CI 0.64-1.51, P = .941; OR = 0.84, 95% CI 0.65-1.08, P = .168). MR analysis indicated increased genetic risk of T1DM in children with asthma (OR = 1.308; 95% CI 1.030-1.661; P = .028). Analysis using the IVW method indicated no association between T1DM and genetic risk of asthma (OR = 1.027, 95%CI 0.970-1.089, P = .358).

CONCLUSION

Both meta-analysis and MR study suggested that childhood asthma was a risk factor for T1DM. No epidemiological or genetic evidence was found for an association of T1DM with asthma incidence. Further studies could be carried out to leverage this newfound insight into better clinical and experimental research in asthma and T1DM.

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

PURPOSE

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.

METHODS

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.

RESULTS

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).

CONCLUSION

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.

Prevalence of asthmatic symptoms in Lebanese patients with type 1 diabetes and their unaffected siblings compared to age-matched controls

Patients with type 1 diabetes (a TH1 disease) have been reported to be at a lower risk of developing asthma (a TH2 disease). Both diseases are affected by environmental and genetic factors. Our objective is to examine this relationship in Lebanon, a Middle-Eastern country, where no previous similar studies are available. This is a cross-sectional observational study conducted at the Chronic Care Center, a referral medical center for type 1 diabetics. Patients with type 1 diabetes aged 6-39 years old, their unaffected siblings and age-matched control completed the International Primary Care Airways Group asthma screening questionnaire. The prevalence of asthma symptoms was compared among the three groups and separately within a subgroup of diabetics in relation to their carrier state of previously collected genetic data. Among 305 diabetics, 776 siblings and 187 controls, diabetics were at lower risk of having any asthma symptoms than controls; OR 0.48 (95% CI 0.32-0.72, p < 0.001) and siblings were at lower risk than diabetics and controls; OR 0.64 (95% CI 0.45-0.91, p = 0.01) and 0.28 (95% CI 0.19-0.42, p < 0.001), respectively. Among 66 diabetics, carriers of the HLA-DQB1*0201 allele were at lower risk of having any asthma symptoms than non-carriers (25.5 vs. 53.3%, p = 0.04). Only a statistically non-significant trend of higher risk was observed in carriers of HLA-DQB1*0301 and G allele at the 49 (A/G) nucleotide of CTLA-4 gene. The TH1-TH2 paradigm might partially explain these findings, since siblings were the least to report asthma symptoms. Future research is needed with diagnostic tests for asthma and extensive genetic testing.

A meta-analysis of the association between childhood type 1 diabetes and atopic disease

OBJECTIVE

To review the published literature and perform a meta-analysis summarizing the evidence in support of an inverse association between type 1 diabetes and the atopic disorders: asthma, eczema, and allergic rhinitis in children.

RESEARCH DESIGN AND METHODS

MEDLINE, Web of Science, and PubMed were searched to identify relevant studies. These were assessed on quality criteria, and odds ratios (ORs) and 95% CIs were calculated for each study from the reported prevalences of atopy in children with diabetes and in control children. Meta-analysis was then used to derive a combined OR and test for heterogeneity in findings between studies.

RESULTS

Twenty-five studies were identified. Heterogeneity in the findings from different studies was evident but was considerably reduced when the asthma and rhinitis analyses were restricted to those studies judged to be of adequate design. The meta-analysis revealed an inverse association between asthma and type 1 diabetes, but the finding only attained significance when analysis was restricted to the studies of adequate design (OR 0.82, 95% CI 0.68-0.99). In this subset an association of similar magnitude was observed between eczema and type 1 diabetes (0.82, 0.62-1.10) although this failed to attain statistical significance, and heterogeneity between studies was still present. There was little evidence of an association between rhinitis and type 1 diabetes (0.97, 0.82-1.16) in this subset of studies.

CONCLUSIONS

Our analysis suggests that there is a small but significant reduction in the prevalence of asthma in children with type 1 diabetes, but the findings for the other atopic diseases are less conclusive.