Just 2
days of sleep loss may trigger changes in gut microbiota that are associated
with poor metabolic health. This is the finding of a small study published in
the journal Molecular Metabolism.
For
optimal health and well-being, the American Academy of Sleep Medicine recommend
adults aged 18-60 years get at least 7 hours of sleep every
night.
However, earlier this year, a report from the Centers for Disease Control
and Prevention (CDC) revealed that more than a third of adults in the United
States are not meeting these recommendations.
Lack of sleep has been linked to increased risk of
numerous health problems, including high
blood pressure, stroke, heart
disease, obesity, and type 2 diabetes.
Previous
research has also associated changes in gut microbiota - the community of
microorganisms that reside in the digestive tract - with obesity and type 2
diabetes. Whether sleep loss plays a role in this relationship, however, has
been unclear.
According
to the researchers of the new study - including first author Christian Benedict
of the Department of Neuroscience at Uppsala University in Sweden - some
studies in mice and humans have suggested that gut bacteria have a circadian
rhythm that might be disrupted by sleep loss.
"However,
to date, there are no studies that have investigated the impact of insufficient
sleep on the composition of the human gut microbiota," they add.
"Studies are therefore lacking that assess whether
important adverse metabolic changes that may increase the risk of [type 2
diabetes] and obesity, such as impaired insulin sensitivity, are associated with
changes in the gut microbiome and associated SCFAs [short chain fatty acids]
that could result from recurrent sleep loss."
Restricted
sleep linked to obesity-associated changes in gut microbiota
To
find out more about the link between sleep loss, gut microbiota, and metabolic
changes, Benedict and team enrolled nine healthy, normal-weight males to their
study.
The
researchers analyzed fecal samples from the men after two sleep conditions: 1
day of normal sleep (around 8 hours) and 2 days of restricted sleep (around 4
hours each night).
Meal
times and food intake can affect the composition of gut bacteria, so these were
kept consistent across both sleep conditions.
While
the team found no evidence that sleep loss alters the diversity of gut
bacteria, their analysis did identify changes in microbiota - such as an
increase in the ratio of Firmicutes to Bacteriodetes -
that previous studies have associated with obesity.
Additionally,
the researchers found that following sleep restriction, subjects showed a 20
percent reduction in sensitivity to insulin - the hormone that regulates blood
glucose levels.
"This
decreased insulin sensitivity was however unrelated to alterations in gut
microbiota following sleep loss," says Benedict. "This suggests that
changes in microbiota may not, at least in the short-term, represent a central
mechanism through which one or several nights of curtailed sleep reduce insulin
sensitivity in humans."
While these findings suggest sleep loss can trigger changes
in gut bacteria, the researchers say further investigation is warranted to
better understand whether these changes influence metabolic health.
The
authors add:
"Given our small sample size
that only involved healthy young men, larger and more long-term studies are
required to investigate to what extent these findings persist over longer time
periods and whether these are observed in females, older or diseased patients
and in other sleep restriction paradigms.
Nevertheless, our study is the first to provide evidence for
sleep deprivation-induced changes in microbial families of bacterial gut
species, which have previously been linked to metabolic pathologies."
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