Is There an Association Between Type 1 Diabetes and Impaired Pulmonary Function?

Type 1 diabetes (T1D) is associated with impaired pulmonary function, independent of sex, age, smoking status, body mass index (BMI), and geographic locale, according to the results of a meta-analysis published in the Respiratory Medicine.

It is well known that T1D affects all organs of the body, with a number of studies demonstrating pulmonary microcirculation disorders and fibrotic changes in the lungs among patients with the disorder. Hypothesizing that the lung might be a target organ of T1D, researchers conducted an exhaustive literature search and meta-analysis exploring the association between T1D and pulmonary function tests. They also carried out a sensitivity analysis based on the publication date of the study, size of the group with T1D, and quality of the study.

A total of 39 studies from multiple countries were included in the meta-analysis, including 35 case-control studies, 3 cross-sectional studies, and 1 longitudinal study. These studies comprised a total of 1274 patients with T1D and 1353 control participants (age range, 10.0 to 50.7 years; 42.3% female). Studies were classified as good, fair, or poor; although all studies were included in the meta-analysis, the sensitivity analysis included only studies deemed to be good quality.

The pooled mean difference (MD) for pulmonary function measures among these patients was as follows:

1. Predicted percentage of forced expiratory volume in 1 second (FEV₁; MD, –6.40; 95% CI, –8.55 to –4.25; P <.001);
2. Forced vital capacity (FVC; MD, –6.39; 95% CI, –8.46 to –4.33; P <.001);
3. Forced expiratory flow between 25% and 75% of total lung capacity (FEF_25%-75%; MD, –6.14; 95% CI, –10.73 to –1.56; P =.009);
4. Peak expiratory flow (PEF; MD, –9.32; 95% CI, –14.15 to –4.50; P =.0002); and
5. Diffusing capacity of the lungs for carbon monoxide (DL_CO; MD, –0.64; 95% CI, –1.12 to –0.16; P =.008).

No difference in the ratio of FEV₁/FVC (MD, –0.33; 95% CI, –1.70 to 1.03; P =.28) was reported.

Notably, the investigators found considerable heterogeneity among the studies that upon metaregression was not explained by patient age, sex, BMI, smoking or geographical region.

Limitations of the meta-analysis included: resolution of discrepancies in study selection and quality assessment via consensus, rather than by calculating Cohen’s kappa; heterogeneity between studies; and the small number of studies providing data that were separated according to sex.

Findings of the meta-analysis and sensitivity analysis were consistent. The researchers concluded, “Our meta-analysis shows that all of the pulmonary function test results, except the FEV₁/FVC ratio, were decreased for the patients with T1D.” Although the significance of impaired lung function in those with T1D is still unknown, they added, “we think that pulmonary function impairment in T1D is relevant, and prospective longitudinal studies are necessary to elucidate the progression of patients with diabetes and pulmonary impairment.”  

Reference

Diez-Manglano J, Samper UA. Type-1 diabetes and pulmonary function tests: a meta-analysis. Respir Med. Published online September 22, 2022. doi:10.1016.j.rmed.2022.106991