Abstract
- Background
Probiotics are live microorganisms that may confer beneficial physiological effects when administered in adequate amounts, with some clinical trials demonstrating their ability to prevent respiratory infections. Although a previously published Cochrane review indicated the benefits of probiotics for acute upper respiratory tract infections, several new studies have emerged, prompting this updated systematic review first published in 2011 and updated in 2015.
- Objectives
To assess the effectiveness and safety of probiotics, using any specified strain or dose, compared with placebo or no treatment, in preventing acute upper respiratory tract infections across individuals of all ages at risk of infection.
- Methods
A comprehensive literature search was conducted across multiple databases—including CENTRAL, MEDLINE, Embase, Web of Science, and Chinese biomedical literature and dissertation databases—alongside international clinical trials registries up to May 2022. Individual randomized controlled trials and cluster-randomized controlled trials comparing probiotics with placebo or no treatment for preventing acute upper respiratory tract infections in community, care facility, school, or hospital settings were selected. Data collection and analysis followed standard Cochrane methodological procedures using a random-effects model, with risk ratios for dichotomous outcomes and mean differences for continuous outcomes, evaluated via the GRADE approach.
- Results
Twenty-three individual randomized controlled trials and one cluster-randomized controlled trial involving a total of 6,950 participants—including children, adults, and older people—were included. Most studies evaluated one or two strains administered at daily doses ranging from $10^{9}$ to $10^{11}$ colony-forming units for more than three months. Meta-analysis indicated that probiotics may reduce the number of participants diagnosed with upper respiratory tract infections experiencing at least one event (risk ratio: 0.76; 95% confidence interval: 0.67 to 0.87; $P < 0.001$) and likely reduce those experiencing at least three events (risk ratio: 0.59; 95% confidence interval: 0.38 to 0.91; $P = 0.02$). Furthermore, probiotics may reduce the incidence rate of infections, shorten the mean duration of an episode by over one day, likely decrease the number of participants prescribed antibiotics, and show little to no increase in adverse events compared to control groups.
- Conclusions
Overall, probiotics are more effective than placebo or no treatment in preventing acute upper respiratory tract infections, demonstrating a favorable safety profile.
https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006895.pub4/full