Our results corroborate the idea that sleep does not only impact brain function, but also interacts with our immune system and metabolism, Vilma Aho says.
Population-level studies have indicated that insufficient sleep increases the risk of cardiovascular diseases and type 2 diabetes. These diseases are known to be linked to inflammatory responses in the body.
University of Helsinki researchers have now shown what kinds of biological mechanisms related to sleep loss affect the immune system and trigger an inflammatory response. The study was published in PLOS ONE journal.
Conducted at the sleep laboratory of the Finnish Institute of Occupational Health, the study restricted the amount of sleep of a group of healthy young men to four hours per night for five days, imitating the schedule of a normal working week. Blood samples were taken before and after the sleep deprivation test.
White blood cells were isolated from the samples, and the expression of all genes at the time of the sampling was examined using microarrays. The results were compared with samples from healthy men of comparable age who had been sleeping eight hours per night for the week.
– We compared the gene expression before and after the sleep deprivation period, and focused on the genes whose behaviour was most strongly altered, explains researcher Vilma Aho.
The expression of many genes and gene pathways related to the functions of the immune system was increased during the sleep deprivation. There was an increase in activity of B cells which are responsible for producing antigens that contribute to the body’s defensive reactions, but also to allergic reactions and asthma.
– This may explain the previous observations of increased asthmatic symptoms in a state of sleep deprivation, Aho says.
The amount of certain interleukins, or signalling molecules which promote inflammation, increased, as did the amount of associated receptors. CRP level was also elevated, indicating inflammation.
For the follow-up study, researchers used material from the national FINRISKI health survey. Participants in this population study underwent blood tests but also answered questions about their health, for example whether they were getting enough sleep.
– Some of the gene-level changes observed in the experimental working week sleep restriction study were repeated in the population sample, Aho tells.