Researchers at the University of Illinois, Chicago, have recently published research demonstrating that disrupted sleep leads to elevated blood pressure and alterations to the bacterial microbiome.[i] I’ve been covering this subject for a while as I myself am a terrible sleeper, and have a life long history of irritable bowel…and sleep and IBS go hand-in-hand all too often. I’ve pointed out in past posts (like this one, for example) that research shows that alterations to the bacterial microbiome lead to disrupted sleep, and disrupted sleep leads to higher levels of inflammation which adversely affect the gut flora. In this study, the scientists looked at long term (28 day) sleep disruption in an animal model. The rats had their sleep disrupted while having their brain activity, blood pressure and heart rates monitored. The researchers also analyzed their fecal microbial content. There was a control group of animals used for comparison.
They noted that the rats had an increase in blood pressure which lasted (for an as yet unspecified period of time) even after the animals were permitted to return to normal sleep. Likewise, they noted that the disrupted sleep led to adverse microbiome alterations, as has been shown in previous research. (ugh) The microbiome shift, however, did not take place immediately: it took a week for these alterations to start. And when they did, the scientists noted an increase in species associated with higher levels of inflammation, as per prior findings. (double ugh)
Some specifics: they noted that in the intervention group, short chain fatty acid (SCFA) production was altered, there was less bacterial diversity, there was a lower ratio of Firmicutes to Bacterioidetes species, and there were higher levels of Proteobacteria, as compared to the controls. There were also certain fecal metabolites that are significantly correlated with high blood pressure.
Previous research has shown that metabolites produced by gut bacteria, like SCFAs and something called succinate, can increase blood pressure. It’s also known that sleep fragmentation (SF) is linked to adverse cardiovascular changes in both rodents and humans, and in rodents, it’s also documented that disrupted sleep leads to changes in the endothelial lining of the gut. In humans, disrupted sleep is specifically associated with cardiovascular issues like arterial stiffness, hypertension and as well as metabolic syndrome and more.
There are 3 novel findings in this research: 1. The degree of arterial pressure is directly linked with the amount of sleep that is lost (the more sleep lost, the higher the blood pressure); 2. After a week of fragmented sleep, changes in the gut microbiota are apparent including a reduction in diversity, altered ratios of bacteria (as noted above), an increase in the abundance of Proteobacteria, and the relative abundance of butyrate-producing bacteria. 3. The relative abundance of certain bacteria (those that produce acetate and succinate) as well as several fecal metabolites are correlated with arterial pressure.
To sum up: sleep fragmentation seems to affect blood pressure without microbiome influence at first, but the gut microbiome is “clearly impacted” by extended periods of fragmented sleep. Understanding these changes is really important because it provides a means, hopefully, of preventing cardiovascular disease, etc. in both night-shift workers as well as those with sleep disorders including sleep apnea (untreated, sleep apnea is well known to lead to potentially fatal cardiovascular events). This is a really interesting point, from the conclusion of this paper: this research, “…provides insights indicating that changes to the gut microbiota from SF are not unidirectional, and alterations in specific metabolite producing bacterial populations are dependent on the ‘dose’ of SF and blood pressure elevation.” That is, the severity of the sleep fragmentation matters. The less sleep you get, the worse off you are.
Says one of the authors of the paper, “We hope to find an intervention that can help people who are at risk for cardiovascular disease because of their work and sleep schedules. People will always have responsibilities that interrupt their sleep. We want to be able to reduce their risk by targeting the microbiome with new therapies or dietary changes…”[ii]
[i] Katherine A. Maki et al, Sleep fragmentation increases blood pressure and is associated with alterations in the gut microbiome and fecal metabolome in rats, Physiological Genomics (2020). DOI: 10.1152/physiolgenomics.00039.2020