Changes in the human gut microbiome, sometimes referred to as the body's “second brain,” may signal imminent death. That’s the upshot of a preliminary study that zooms in on human fecal matter as potential predictor of mortality.

In the experiment, researchers used fecal matter to sequence and identify the population of micro-organisms living in humans' gut microbiomes. The resulting microbiome profiles enabled the team to accurately predict when participants in the study had died across a 15-year period. In addition, they found that participants with an unusually high amount of a certain kind of bacteria were 15 percent more likely to die in the next 15 years as the other study participants.

The findings were published earlier this month on the preprint server MedRxiv.

The research hasn’t been peer reviewed, so the paper can't be taken as conclusive evidence that the gut microbiome can predict your time of death. But the findings offer a tantalizing clue to the power of the microbiome as a measure of overall health and longevity.

The study includes 7,211 Finnish people who took part in the FINRISK survey in 2002. The participants filled out questionnaires capturing their medical histories and lifestyle. They also completed physical exams and gave blood — and stool — samples.

The researchers compared individuals' fecal microbes with their death certificates — if there was one — and health records. Some 10.2 percent of the participants had died over the course of the study period, which lasted 14.2 years.

The team looked at thousands of different microbes living in the participants’ guts and present in their stool, including bacteria and viruses. They found that one bacteria — Enterobacteriaceae — appeared to be more associated with death than others. The bacteria is common in the gut microbiome and related to the bacteria that cause infectious diseases like E. coli and salmonella. They are abundant in the microbiomes of people with irritable bowel syndrome and colorectal cancer.

Compared to other microbes, the presence of enterobacteriaceae in fecal matter was a “strong predictor” of death from any cause during the study period. People with a high proportion of the bacteria in their microbiome were 15 percent more likely to die within the study period than their peers, the researchers found.

The researchers report a “robust link” between mortality and this bacteria, but more research is needed before any conclusions about the presence of enterobacteriaceae and increased risk of death can be drawn. The research also doesn't answer whether the presence of this bacteria is a signal of disease or another risk factor that might up one’s chances of impending death.

Extensive research is “still warranted before human microbiome sequencing can be used for prediction, prevention, and targeted treatment of disease,” the researchers say.

If the provocative findings are confirmed, it may be possible to leverage the gut microbiome to predict lifespan — and help prevent disease that may prove fatal. Eventually, analyzing the microbes in feces may become a potentially “cost-effective, consistent, and non-invasive” way to predict health outcomes, the researchers say.

Abstract: The collection of fecal material and developments in sequencing technologies have enabled cost-efficient, standardized, and non-invasive gut microbiome profiling. As a result, microbiome composition data from several large cohorts have been cross-sectionally linked to various lifestyle factors and diseases. In spite of these advances, prospective associations between microbiome composition and health have remained uncharacterized due to the lack of sufficiently large and representative population cohorts with comprehensive follow-up data. Here, we analyse the long-term association between gut microbiome variation and mortality in a large, well-phenotyped, and representative population cohort (n = 7211, FINRISK 2002; Finland). We report specific taxonomic and functional signatures related to the Enterobacteriaceae family in the human gut microbiome that predict mortality during a 15-year follow-up. These associations can be observed both in the Eastern and Western Finns who have differing genetic backgrounds, lifestyles, and mortality rates. Our results supplement previously reported cross-sectional associations, and help to establish a methodological and conceptual basis for examining long-term associations between human gut microbiome composition, incident outcomes, and general health status. These findings could serve as a solid framework for microbiome profiling in clinical risk prediction, paving the way towards clinical applications of human microbiome sequencing aimed at prediction, prevention, and treatment of disease.