Ian Buller

Ph.D., M.A.

National Cancer Institute

Postdoctoral Fellow

PLCO (Learn more about this study)

PLCO-749

Mar 15, 2021

Geographic variation of the oral microbiome in the United States: A spatial analysis in three prospective cohorts

Communities of microbial organisms inhabit the human body but vary in their composition and density across individuals. Understanding these differences is a chief pursuit of human microbiome research in part because the human microbiome has been linked to various health outcomes, including cancer incidence and mortality. In addition to dissimilar lifestyles and diet, variation in the geographic location of persons may explain the variation in their microbiome. However, spatial scale is a common yet important consideration for assessing geographic variation because patterns at large and small spatial scales are often discordant. Few studies have evaluated geographic variation in the human microbiome, primarily at large spatial scales. Geographically-varying lifestyle factors such as, for example, diet and hygiene, may also explain the oral microbiota variation between countries. Further, few studies have evaluated smaller-scale variation or geographic clustering in human microbial diversity, where clustering is the tendency for microbiota to be increasingly similar the closer they are geographically located. To our knowledge, no study has examined regional variation in or geographic clustering of the microbial diversity of the human oral cavity within the U.S.

The microbial community in the oral cavity has been linked to cancer. As described in a recent review, multiple species of oral bacteria have been identified as indicators of various cancers of the oral cavity, colon, pancreas, and lungs. These associations are still tentative and are an active area of research, including methodological studies to develop consistent collection protocols and other methods. Additionally, these studies did not account for potential geographic variation in oral microbial diversity among their study participants. An understanding of the underlying geographic distribution of the oral microbiome and its potential covarying factors can potentially inform future studies investigating the link between the oral microbiome and health outcomes, including cancer.

A limited understanding and mixed evidence from a small number of studies regarding geographic variation and other covarying lifestyle factors in the human oral microbiome provide justification for a descriptive evaluation of geographic variation of the microbiota in the human oral cavity in the U.S. In collaboration with several branches within the Division of Cancer Epidemiology and Genetics (DCEG), we will leverage an existing case-cohort study that includes participants spanning 18 states and metropolitan areas to evaluate the geographic variation in the oral microbiota of study participants.