Why does lack of sleep increase risk of diabetes, heart disease and
11 November 2013
University of Helsinki researchers have discovered new biological
links between sleep loss and the immune system. The results help
explain why sleep deprivation increases the risk of inflammatory
diseases such as cardiovascular disease, type 2 diabetes and asthma.
Population-level health studies have previously indicated that
insufficient sleep increases the risk of cardiovascular diseases and
type 2 diabetes, which are known to be linked to inflammatory
responses in the body.
The University of Helsinki Sleep Team has now shown what kinds of
biological mechanisms related to sleep loss affect the immune system
and trigger an inflammatory response. They identified the genes
which are most susceptible to sleep deprivation and examined whether
these genes are involved in the regulation of the immune system. The
study was published in the PLOS ONE journal on 23 October 2013.
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,” explained 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.”
The amount of certain interleukins, or signalling molecules which
promote inflammation, increased, as did the amount of associated
receptors such as Toll-like receptors (TLR). On the gene level, this
was apparent in the higher-than-normal expression of the TLR4 gene
after sleep loss. CRP level was also elevated, indicating
The researchers also examined the impact that long-term sleep
deprivation could have on the immune system. For this follow-up
study, they 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.
The researchers compared participants who believed they were
sleeping sufficiently with those who felt that they were not
sleeping enough. Some of the gene-level changes observed in the
experimental working week sleep restriction study were repeated in
the population sample. These results may help explain the connection
between shorter sleep and the development of inflammatory diseases,
such as cardiovascular disease and diabetes, which has been
established in epidemiological studies.
“These results corroborate the idea that sleep does not only
impact brain function, but also interacts with our immune system and
metabolism. Sleep loss causes changes to the system that regulates
our immune defence. Some of these changes appear to be long-term,
and may contribute to the development of diseases that have been
linked to sleep deprivation in epidemiological research,” Aho said.
Aho V et al. Partial Sleep Restriction Activates Immune
Response-Related Gene Expression Pathways: Experimental and
Epidemiological Studies in Humans. PLOS ONE 23rd Oct, 2013.