Lack of sleep has been said to have a similar effect on concentration and performance as being drunk and can lead to higher levels of stress, anxiety, and depression and also to unnecessary risk-taking. Although sleep deprivation is known to impair performance and have negative effects on learning and memory, the molecular mechanisms underlying changes in brain function remain poorly understood.
Researchers at the University of Pennsylvania, the University of Glasgow and the University of Toronto have now shown that brief sleep deprivation in mice leads to increased levels of PDE4 and reduced levels of cAMP in the hippocampus, an area of the brain associated with learning and memory. When the mice were treated with the PDE4 inhibitor, rolipram, cAMP signalling was restored, together with synaptic plasticity and hippocampus-dependent memory. The team hope that their findings, which are published in the journal Nature, will lead to new treatments for the cognitive impairment that accompanies sleep disturbances seen in disorders such as sleep apnea, Alzheimer’s disease and schizophrenia.
PDE4 is the major cAMP-metabolising enzyme in inflammatory and immune cells and inhibitors were originally investigated for the treatment of asthma, rhinitis and COPD. Dose-limiting nausea and vomiting have been observed with PDE4 inhibitors, likely because of lack of selectivity for the different isoforms of PDE4, and these side effects will need to be overcome if PDE4 inhibitors are to be used to reduce the impact of sleep deprivation.
The study represents an important advance in understanding how lack of sleep affects our brain and, although many of us may just prefer a decent night’s sleep, could lead to much needed help when lifestyle or illness make this an impossible dream.
A good night’s sleep makes a big difference to how we feel, and a new US study suggests that it could also reduce our risk of catching a cold. People who sleep for fewer than seven hours a night were found to be almost three times more likely to get a cold than those who average eight or more hours a night. Having trouble falling asleep or waking up during the night increased the risk even more.
In the study, 54 out of 153 healthy men and women (average age 37) developed cold symptoms in the 5 days after nasal administration of drops containing a rhinovirus. After 28 days, blood samples were tested for antibodies to the virus and it was found that 135 people had become infected, although not all had developed a cold.
For two weeks before being exposed to the virus, the participants were asked each day about the duration and quality of their sleep. In the five days following exposure to the virus, people who had slept for fewer than seven hours each night in the previous two weeks were almost three times more likely to report symptoms than those who had slept for eight hours or more. Broken sleep was found to be even more important: those who were awake for more than 8% of sleep time were five and a half times more likely to show symptoms than those who were awake for 2% or less of the time. Interestingly, the development of cold symptoms did not correlate with how well rested the subjects felt. After taking into account a wide variety of other factors, how long – and especially how well – individuals slept were the strongest predictors of who would develop a cold. Previous research had suggested a link between sleep deprivation and impaired immune function, but this is the first study to show that sleep disturbances can affect susceptibility to cold viruses in normal healthy people. The study is published in the January 12th edition of Archives of Internal Medicine.