Gut microbiome dysbiosis in chronic lung disease: a systematic review and meta-analysis

Objectives Recent data suggest that the gut–lung axis plays a role in the development of lung disease. However, the potential association between the gut microbiota and chronic lung disease (CLD) remains unclear. This study aimed to investigate changes in the gut microbiome in patients with CLD. Methods We searched PubMed, Web of Science, Cochrane, Embase, China National Knowledge Infrastructure, Wanfang, and VIPC databases from inception to August 1, 2024. The inclusion criteria involved studies that reported on gut flora in patients with CLD. Two independent reviewers used standardized methods to search, screen, and code included studies. Publication bias was analyzed using Egger’s test. Changes in the gut microbiome were assessed through α-diversity, β-diversity, and changes/differences in relative abundance, and results were evaluated using a random-effects model. Results A total of 27 studies were included: 21 on chronic obstructive pulmonary disease (COPD; 1,273 patients and 6,718 healthy controls HCs), six on asthma (559 patients and 5,310 HCs), one on COPD and asthma combined, and one on pulmonary cystic fibrosis. Compared with HCs, α-diversity was decreased in patients with COPD (Shannon index: standard mean difference SMD = −0.38; 95% confidence interval CI, −0.76 to 0.00, I 2 = 72%; n=7). In COPD, Bacteroides was increased (SMD = 0.76; 95% CI, 0.00 to 1.52; I 2 = 91%; n=4), while Bifidobacterium (SMD = −0.88; 95% CI, −1.39 to −0.37; I 2 = 88%; n=5) and Lactobacillus (SMD = -0.73; 95% CI, -1.00 to -0.46; I 2 = 66%; n=5) were decreased. No difference was found in Shannon and Simpson diversity indexes between patients with asthma and HCs. Conclusion The gut microbiota of patients with COPD is imbalanced, and the abundance of probiotics is lower than in healthy individuals. Further exploration of the potential role of probiotics in COPD may provide promising targets for treatment. Systematic review registration https://www.crd.york.ac.uk/PROSPERO/ , identifier CRD42022378296.