Asthma, Type 1 Diabetes Often Co-occur in Children, Families

Miriam E. Tucker

March 25, 2020

Asthma and type 1 diabetes often co-occur in individual children and their family members, new research suggests.

Siblings with either condition were at increased risk for the other compared with the general population.

However, although individuals diagnosed with asthma first, at an average age of 3 years, were at increased risk for a subsequent diagnosis of type 1 diabetes (at an average age of 5.9 years), the reverse wasn't found.

The results "support evidence for a familial risk due to shared factors, despite the possible existence of causal pathways between the two diseases," Awad I. Smew, MD, Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm, Sweden, and colleagues write.

Knowing of this comorbidity between asthma and type 1 diabetes and familial coaggregation extending to siblings "is important in understanding the association between atopic and autoimmune disease and may be of future clinical importance," say the authors.

Additionally, "awareness of the known association between the two diseases is important for physicians treating those patients."

Asthma Diagnosis Increases Likelihood of Type 1 Diabetes

The findings, from Swedish national population databases, were published online March 12 in JAMA Network Open.

Among more than 1 million children born in Sweden from 2001 through 2013, type 1 diabetes and asthma co-occurred often in both individuals and within families.

The study population included 1,284,748 children born over a 13-year period who were linked to their biological parents, full and half siblings, and cousins and half cousins. Overall, 9.5% (121,809) had asthma, 0.3% (3812) had type 1 diabetes, and 0.04% had both.

Those prevalence rates were similar among the siblings: 9.6% had asthma, 0.3% had type 1 diabetes, and 0.04% had both.

The average age at diagnosis of asthma was 3.0 years, and for type 1 diabetes, 5.9 years. Asthma was more common among males (61.8%) but the rate of type 1 diabetes didn't differ by sex (51.7% among males).

After adjustment for sex and date of birth, the overall odds ratio for asthma among those with versus without type 1 diabetes at the end of the follow-up period (through 2015) was 1.15, a significantly increased risk.

By age 8 years, that odds ratio was 1.42, which was also significant.

Among those diagnosed with asthma, the adjusted odds ratio of developing subsequent type 1 diabetes compared to those without previous asthma was 1.17, a significantly increased risk.

In contrast, for those previously diagnosed with type 1 diabetes there was no increased risk for subsequent asthma (adjusted odds ratio, 0.91), however.

Thus, children with both asthma and type 1 diabetes typically had already received their asthma diagnosis before they developed type 1 diabetes, Smew and colleagues reiterate.

The odds ratios for familial coaggregation of both conditions were 1.27 for full siblings, which was significant, and 1.08 for full cousins, of borderline significance, but wasn't significant for the other types of relatives.

The authors acknowledge the possibility that treatment of asthma with inhaled corticosteroids could increase the risk of developing type 1 diabetes.

From a clinical perspective, although more evidence is needed before implementation of guidelines, awareness of the known association between the two diseases is important for physicians treating those patients, the authors say.

"An understanding of the comorbidity could be beneficial in terms of avoiding diagnostic delay by recognizing symptoms of asthma that may otherwise be overlooked by caregivers and physicians in the more acute management of patients with type 1 diabetes," they write.

Financial support for the study was provided through grants from the Swedish Research Council, Swedish Initiative for Research on Microdata in the Social and Medical Sciences framework, Forte, Stockholm County Council, and Swedish Heart-Lung Foundation. The authors have reported no relevant financial relationships.

JAMA Netw Open. Published online March 12, 2020. Full text

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