The researchers studied 9 normal-weight men (mean age 23.3 years) in a randomized within-subject crossover study with fixed meal times and exercise schedules: they examined the subjects after 2 nights of partial sleep deprivation (sleep opportunity 02:45-07:00h) and after 2 nights of normal sleep (sleep opportunity 22:30-07:00h). Faecal samples for microbiota composition and short-chain fatty acid content analysis were collected within 24 hours before (baseline), and after the 2 in-lab nights, of either partial sleep deprivation or normal sleep. Furthermore, participants underwent an oral glucose tolerance test following each sleep intervention.
Overall the researchers did not find evidence that suggested the diversity of the gut microbiota was altered by the sleep restriction, which may be expected due to the short-term nature of the intervention and the small sample size. However, after 2 days of partial sleep deprivation, individuals exhibited an increased Firmicutes:Bacteroidetes ratio and an increase in bacteria from the families Coriobacteriaceae and Erysipelotrichaceae, with decreases in Tenericutes, when compared to normal sleep. Changes in these families of bacterial gut species were previously associated with metabolic perturbations in some studies both in mice and humans. However, faecal short-chain fatty acid levels did not change depending on sleep duration. Fasting and postprandial insulin sensitivity decreased after partial sleep deprivation but were unrelated to alterations in the gut microbiota. This suggests that changes in gut microbiota may not represent a central mechanism by which short-term sleep deprivation reduces insulin sensitivity in humans.
On the whole, these are the first results that show how short sleep duration impacts the human gut microbiota. Further research is needed in order to elucidate the extent to which changes to the gut microbial communities contribute to the known metabolic consequences of sleep loss.
Andreu Prados Andreu Prados holds a Bachelor of Science Degree in Pharmacy & Human Nutrition and Dietetics. Science writer specialised in gut microbiota and probiotics, working also as lecturer and consultant in nutrition and healthcare. Follow Andreu on Twitter @andreuprados