Paradigm Shift of Microbiota-gut-brain Axis During Aging: Potential Role of Probiotics to Improve Cognitive Decline.

Population aging is a global demographic inevitability, driven by advancements in healthcare, increased life expectancy, and declining fertility rates. Growing evidence implicates gut microbiota dysbiosis in the pathogenesis of cognitive impairments and neurodegenerative disorders commonly associated with aging, primarily through disruptions in immune, metabolic, and neuroendocrine signaling along the gut-brain axis. This review synthesizes current literature on the therapeutic potential of probiotic bacteria, such as Lactobacillus and Bifidobacterium, to enhance glial function, maintain blood-brain barrier integrity, and neurocognitive performance in older adults. However, probiotic efficacy is highly strain-specific and context-dependent, necessitating individualized evaluation of each microbial strain's therapeutic profile. Future research should prioritize precision microbiome-based strategies to elucidate mechanisms of action, optimal strain combinations, and their effectiveness across varying degrees of cognitive decline in the aging population. Furthermore, diet, physical activity, and microbial exposures represent essential, non-pharmacological tools for maintaining microbiota eubiosis and supporting neurocognitive health in aging populations.