Efficacy of probiotics on cognition, and biomarkers of inflammation and oxidative stress in adults with Alzheimer’s disease or mild cognitive impairment — a meta-analysis of randomized controlled trials

Abstract

Probiotics are live microbes that confer health benefits to the host. Preliminary animal evidence supports the potential role of probiotics in ameliorating cognitive health, however, findings from clinical trials in Alzheimer's disease (AD) or mild cognitive impairment (MCI) subjects are controversial. Thus, a meta-analysis is needed to clarify the efficacy of probiotics on cognition in AD or MCI patients. EMBASE, PubMed, Web of Science and Cochrane library were systematically searched and manually screened for relevant published randomized controlled trials (RCTs). Among the 890 citations identified, 5 studies involving 297 subjects met eligibility. There was a significant improvement in cognition (SMD = 0.37; 95% CI, 0.14, 0.61; P = 0.002; I 2 = 24%), while a significant reduction in malondialdehyde (SMD = −0.60; 95% CI, −0.91, −0.28; P = 0.000; I 2 = 0.0%) and high-sensitivity Creactive protein (SMD = −0.57; 95% CI, −0.95, −0.20; P = 0.003; I 2 = 0.0%) post-intervention levels between the probiotics and control group. This meta-analysis indicated that probiotics improved cognitive performance in AD or MCI patients, possibly through decreasing levels of inflammatory and oxidative biomarkers. However, current evidence is insufficient, and more reliable evidence from large-scale, long-period, RCT is needed.

Gut microbes in neurocognitive and mental health disorders

“…There is increasing research to study the effects of probiotic supplementation in the treatment of mental health and cognitive disorders. A meta-analysis of randomised controlled trials examining patients with both MCI and AD found significant improvements (p ¼ 0.002) in cognition [159]. As well, a meta-analysis found patients with mood disorders receiving probiotic treatment had significantly lower depression scores (SMD ¼ À0.47, 95% CI: À0.67 to À0.27, p¼0.27) without any significant change in anxiety scores [160].…”

Gut–Brain Axis: Role of Gut Microbiota on Neurological Disorders and How Probiotics/Prebiotics Beneficially Modulate Microbial and Immune Pathways to Improve Brain Functions

“…Additionally, the probiotic intake significantly increased the levels of IL-22 and TRANCE expression at weeks [ 174 ]. A meta-analysis of randomized controlled trials showed that probiotics intake improved cognitive functions in AD and mild cognitive impairment (MCI) subjects, possibly via decreasing the levels of inflammatory and oxidative markers [ 175 ]. In contrast, the meta-analysis of randomized controlled trials showed no remarkable difference between probiotics/prebiotics and placebo in alleviating anxiety and depressive symptoms [ 176 , 177 ].…”

Addition of probiotics to antibiotics improves the clinical course of pneumonia in young people without comorbidities: a randomized controlled trial

“…The concept of probiotics as immune modulators and their various applications for preventing, modifying, or treating diseases have been highlighted. Probiotics affect various organs outside the GI tract, and gut-lung crosstalk may be involved in the probiotic-mediated control of acute respiratory infections 30 , 31 . Viral infections in higher vertebrates elicit potent innate and adaptive host immune responses.…”