Plain language summary
Respiratory tract infections (RTIs) are a leading cause of morbidity and mortality among children worldwide. Probiotics are thought to be able to balance the gut microbiota and interact with the immune system, which may promote resistance against pathogens. There are conflicting results from studies investigating the effect of probiotics on RTI infection. The aim of this systematic review and meta-analysis was to provide the latest and convincing evidence of the effect of probiotic consumption on RTIs in children. 32 studies were included in the qualitative analysis, and 23 in the quantitative meta-analysis. All trials were randomised, double-blinded, and placebo-controlled. Probiotic supplementation had a significant effect on the reduction of number of subjects having at least 1 respiratory symptom episode, on the number of days the children were ill and the number of days absent from day care/school. There was no significant statistical difference of illness episode duration. There was statistical heterogeneity among the trials, and subgroup analysis did not highlight the source of this. It was noted, however, that the probiotic strain, the duration of regimens, administration forms, doses, and follow-up times differed across the included studies, as did the age of children. The authors conclude that probiotic consumption may decrease the incidence and illness duration of RTIs, and that further research is needed to establish optimal probiotic strains, dosing, administration form, time of intervention, and long-time follow-up.
BACKGROUND Respiratory tract infections (RTIs) represent one of the main health problems in children. Probiotics are viable bacteria that colonize the intestine and affect the host intestinal microbial balance. Accumulating evidence suggests that probiotic consumption may decrease the incidence of or modify RTIs. The authors systematically reviewed data from randomized controlled trials (RCTs) to investigate the effect of probiotic consumption on RTIs in children. METHODS MEDLINE/PubMed, Embase, Cochrane Library, and Web of Science were systematically searched for RCTs regarding the effect of probiotics on RTIs in children. The outcomes included number of children experienced with at least 1 RTI episode, duration of illness episodes, days of illness per subject, and school/day care absenteeism due to infection. A random-effects model was used to calculate pooled relative risks, or mean difference (MD) with the corresponding 95% confidence interval (CI). RESULTS A total of 23 trials involving 6269 children were eligible for inclusion in the systematic review. None of the trials showed a high risk of bias. The quality of the evidence of outcomes was moderate. The age range of subjects was from newborn to 18 years. The results of meta-analysis showed that probiotic consumption significantly decreased the number of subjects having at least 1 RTI episode (17 RCTs, 4513 children, relative risk 0.89, 95% CI 0.82-0.96, P = 0.004). Children supplemented with probiotics had fewer numbers of days of RTIs per person compared with children who had taken a placebo (6 RCTs, 2067 children, MD -0.16, 95% CI -0.29 to 0.02, P = 0.03), and had fewer numbers of days absent from day care/school (8 RCTs, 1499 children, MD -0.94, 95% CI -1.72 to -0.15, P = 0.02). However, there was no statistically significant difference of illness episode duration between probiotic intervention group and placebo group (9 RCTs, 2817 children, MD -0.60, 95% CI -1.49 to 0.30, P = 0.19). CONCLUSION Based on the available data and taking into account the safety profile of RCTs, probiotic consumption appears to be a feasible way to decrease the incidence of RTIs in children.