Probiotics improve lung function and QOL in participants with exposure to fine particulate matter air pollution: a randomized, double-blind, placebo-controlled clinical trial

<i>Background</i>: Probiotics have been reported to alleviate pulmonary inflammation through the gut-lung axis. However, their effects on PM_2.5-induced toxic reactions have not yet been well studied. <i>Objective</i>: This study aims to investigate the effects of probiotics on lung function and quality of life in participants exposed to PM_2.5, as well as to explore the potential mechanisms underlying these effects. <i>Methods</i>: 120 volunteers were randomly assigned in a double-blind manner to receive either a placebo or 2.5 × 10⁹ cfu g^-1 LGG probiotics once daily for four consecutive weeks, with a follow-up period of 6 months. An analysis of covariance was conducted for data statistics, using PM_2.5 exposure and baseline measurements as covariates. Least squares means and their 95% confidence intervals were calculated to explore the effect of PM_2.5 exposure on changes in the intestinal microbiota. A mixed linear model analysis was used to construct a model with baseline values and PM_2.5 exposure as covariates to analyse the effects of PM_2.5 on SF-36, COOP/WONCA charts, and lung function, and the intervention effect of LGG on these parameters. <i>Results</i>: 120 participants were included. Probiotic intervention demonstrated benefits in the Shannon index and β diversity. After the probiotic intervention, the scores of quality-of-life charts increased during the follow-up period. The pulmonary function indicators, including FEV1, FEF50%, and FEF75%, were statistically different from those in the placebo group. <i>Conclusion</i>: Probiotic intervention can reshape the gut microbiota, offering potential benefits for improving the quality of life in participants chronically exposed to PM_2.5.