Our guts are full of resident microbes that make up our “gut microbiome”. The microbiome ecosystem plays a significant role in our health and likely impacts how well we age. Generally, a diverse microbiome is a healthy microbiome and greater diversity associates with greater health. In this study we evaluated how the microbiome changes as we age and how that change may be different in healthy older individuals relative to less healthy. Typically, there are a few abundant species that make up a large portion of the microbiome with thousands of other species having lower representation. We found that in healthy aging a few of these dominant species decreased over time so that the diversity of the microbial community increased. Additionally, this increase in diversity was highly unique in individuals who experienced healthy aging—meaning not only did diversity increase within each healthy-aging individual, but their microbiomes became very different from each other as well.

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Results roundup:

• Alpha diversity is a measure of how diverse a gut microbiome community is within an individual. Beta diversity is a measure of how unique an individual's gut microbiome community is compared to other people’s gut microbiomes. We found that healthy aging is associated with increases in both alpha and beta diversity over time—becoming more diverse within an individual and more unique compared to other individuals.
• Healthy aging was evaluated based on five metrics: medication use, self-perceived health, walking speed, life space score (a measure of mobility), and a composite score of the previous four. Healthy aging was associated with increased microbiome diversity after age 50 and became more pronounced as aging continued into the 70s and 80s.
• Decreased levels of Bacteroides, a dominant microbe in younger people, was the primary driver for increasing the diversity of the microbiome community.
• Individuals that did not show age-related increases in diversity had lower survival rates over time.

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https://doi.org/10.1038/s42255-021-00348-0

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