Study: Causal Relationship Found Between Pneumonia, Gestational Diabetes

A causal association between bacterial pneumonia and gestational diabetes has been found, with additional data suggesting a plausible causal link between pneumonia and type 1 diabetes (T1D), according to a study published in Islets. In the study, investigators used mendelian randomization (MR), which uses genetic variation as a major variable, to determine causal associations between exposures and outcomes in randomized control trials.¹

In a study published in the American Journal of Obstetrics & Gynecology, the study authors reported that pregnant women with pneumonia had an increased risk of low birthweight, preterm birth, small size for gestational age, cesarean section, and preeclampsia/eclampsia, at 1.73, 1.71, 1.35, 1.77, and 3.05, respectively.² They also reported that the mechanisms behind these results were not known.²

The authors of the current study indicated that they explored the relationship between bacterial pneumonia and subtypes of diabetes through MR analyses of 2-sample. The MR tests need to demonstrate single-nucleotide polymorphisms (SNPs) that are strongly correlated with exposure; SNPs that are not directly related to outcomes; SNPs that are not associated with possible confusing factors; and contains no genetic assortative mating, according to the study’s methods. Data from genome-wide associated studies were used, with SNPs selected as the instrumental variables for bacterial pneumonia and included either T2D, T1D, or other forms of diabetes, including gestational diabetes.¹

Investigators identified 20 SNPs that were significantly associated with bacterial pneumonia; however, they found no significant associations with any form of diabetes. The results showed that 11, 13, 104, and 94 SNPs were identified as instrumental variables for gestational diabetes, T1D, T2D, and other types of diabetes, respectively, in reverse MR studies, according to the study authors.¹

The results of the study demonstrated a strong causal relationship between both bacterial pneumonia and gestational diabetes as well as T1D. The weighted median for gestational diabetes and T1D yielded the same results as the instrumental variable weighting analysis. Both types of diabetes did not have the same results with MR-Egger intercept. There was no association observed between causal relationships with T2D or other types of diabetes, according to the study authors.¹

In the MR analysis, the results indicated that gestational diabetes had significant instrumental variable weighting results when exposed to bacterial pneumonia. Investigators concluded that the results supported the occurrence of bacterial pneumonia’s attribution to gestational diabetes. However, the MR analysis did not show any causal relationship between T1D, T2D, and other types of diabetes when exposed to bacterial pneumonia.¹

The study authors concluded that these results showed a bidirectional causal connection between gestational diabetes and bacterial pneumonia, according to the results of the MR and reverse MR analyses. They also added that the results of this study, and other bodies of evidence, have shown the significance of diabetes as a risk factor for various severe infections. The investigators indicated that, due to their data and other similar data regarding the association with diabetes and bacterial pneumonia, additional randomized clinical trials are required to further understand the causality. While their findings do suggest a plausible causal link between bacterial pneumonia and T1D, further studies will be needed to confirm these results.¹

Reference

1. Pan S, Zhang Z, Pang W. The causal relationship between bacterial pneumonia and diabetes: a two-sample mendelian randomization study. Islets. 2024;16(1):2291885. doi:10.1080/19382014.2023.2291885
2. Chen YH, Keller J, Wang IT, Lin CC, Lin HC. Pneumonia and pregnancy outcomes: a nationwide population-based study. Am J Obstet Gynecol. 2012;207(4):288.e1-288.e2887. doi:10.1016/j.ajog.2012.08.023