The Effects of Aging on Gut Microbiome Composition and Association With Age-Related Disease States: A Literature Review

Abstract

Introduction: The gut microbiome is the collection of microbial species residing in the gastrointestinal tract that play an important role in metabolism and immune function. A reduction in microbial diversity and/or an altered composition of microbiota results in dysbiosis, which is speculated to place individuals at greater risk for neurological, metabolic, and physical disorders. The purpose of this study is to provide a review of the literature describing alterations in composition and species richness that occur during aging in the gut microbiome whilst identifying how these changes are linked to age-related diseases.

Methods: A review of the current literature was conducted by searching for applicable keywords using scientific, electronic databases. Keywords used to search for articles included (“gut microbiome” OR “gut microbiota” OR “bacteria flora”) AND (“aging” OR “ageing” OR “old age”) AND (“age-related disease” OR “disease”). Articles were screened and chosen for analysis based on the quality and relevance of the study.

Results: There are many changes that occur in the gut microbiome with aging, such as reduced short-chain fatty acid production, lack of overall diversity and increase in pathobionts from phyla Proteobacteria and Enterobacteriaceae. Many age-related diseases display distinct changes in microbiome composition which have been shown to be implicated in disease onset or progression. In cases of extreme longevity, the microbiome displays specific signatures associated with youthfulness and health such as stability, resilience, and taxonomic diversity.

Discussion: The alterations observed in the gut microbiome during aging are likely due to a concurrent deterioration of the immune system and reduction in intestinal function and motility. Microbial dysbiosis promotes a pro-inflammatory state in the gut which has implications for disease. Additionally, many microbial signatures of aging coincided with alterations attributed to diseased states, further supporting that dysbiosis in later years of life may accelerate or promote pathology. In contrast, the microbiome of centenarians and extremely long-lived individuals demonstrate a model for healthy aging and longevity.

Conclusion: The findings from this study highlight the importance of the microbiome in age-related diseases and proposes the microbiome as a potential target for the mitigation and treatment of disease in elderly populations.