Evidence reveals that diabetes mellitus (DM) could induce inflammatory and fibrotic changes in the lungs. Moreover, a large European study recently found that DM is one of several diseases associated with idiopathic pulmonary fibrosis (IPF)-related mortality. Several observational studies have also reported on the association between DM and IPF, yielding heterogeneous results. However, a comprehensive systematic review combined with pooled analysis was urgently needed to adequately evaluate their true association. Therefore, we conducted a study-level pooled analysis from updated published evidence.

For a paper published in the Journal of Clinical Endocrinology & Metabolism, we and our colleagues compared the prevalence of DM among patients with IPF with that of individuals without IPF, and the prevalence of IPF among patients with DM with that of individuals without DM. We conducted a literature search through January 2021, identifying observational studies, including cohort, cross-sectional, and case-control studies. Ultimately, 16 studies with a total of 25,180 individuals with IPF and 73,434 controls were included and evaluated for the prevalence of DM among individuals with and without IPF. Two studies evaluated the prevalence of IPF among individuals with DM. In total, more than 26 million participants were evaluated in the two analyses.

1.54 Times Increased Odds of DM

We found that people with IPF had increased odds of DM when compared with non-IPF controls, whereas patients with DM showed a slight decrease in the risk for developing IPF. The overall pooled OR of DM in individuals with IPF compared with non-IPF controls suggests that people with IPF have 1.54 times increased odds of DM. However, significant heterogeneity was observed across the included studies (I2=90.7%), and thus, the results should be interpreted with caution (Figure).

Moreover, our results indicate that the prevalence of DM among individuals with IPF compared with non-IPF controls is greater for people with a mean age of younger than 65. This finding is stable around the globe, as well as in hospital-based and population-based subjects.

Early Detection of DM in Patients With IPF Is Critical

Our findings have important implications for physicians, particularly endocrinologists and pulmonologists. Although the exact mechanism of the association between DM and IPF is not clear, our study shows that early detection of DM in patients with IPF is critical so that immediate and adequate therapy can effectively slow disease progression and improve patients’ quality of life. As the prevalence of prediabetes and undiagnosed DM are both increasing, a closer relationship between endocrinologists and pulmonologists is needed, not only to better understand the deleterious effects of DM on lung parenchyma, but also to successfully target pulmonary dysfunction. Therefore, we suggest that physicians form a multidisciplinary team to supervise and control these diseases and manage related complications. Pulmonologists should be familiar with, monitor, and report the condition of patients with IPF and the likelihood of developing DM, and in the process of long-term management of patients with DM, endocrinologists should be aware of IPF caused by lung damage.

Due to the limited number of studies investigating the prevalence of IPF in patients with DM, we cannot draw a complete and valid conclusion about whether patients with DM have an increased risk for IPF. Therefore, future large, prospective, cohort studies investigating the prevalence of IPF in patients with DM are warranted. In addition, further studies are needed to explore the mechanism of interaction between DM and IPF to help further develop targeted treatment.