Not getting enough sleep before having surgery may increase post-operative pain. This suggests that improvements in recovery time may require good amounts of sleep not just after an operation but also before going under the knife.
at Johns Hopkins University in Maryland and her colleagues assessed post-operative pain outcomes in sleep-deprived mice to determine how sleep can affect the healing process.
The researchers kept six mice from falling asleep for 9 hours before surgery with several distractions. They introduced new nesting materials and objects the mice had never seen before into their cages, and occasionally tapped on the cage as well. Afterwards, they gave them an anaesthetic and made an incision in the rodents鈥� hind paws before stitching the wound closed.
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For the next two weeks, the team measured pain daily in the mice by stroking nylon fibres against their wounds. Each fibre placed a different amount of pressure on the injury, and the researchers tracked how much force was needed before the animals retracted their paw. If minimal force made the mice pull away, it indicated greater pain sensitivity.
The researchers found that, starting five days after surgery, mice that had previously been sleep deprived showed greater sensitivity to pain compared with an equal number of animals who slept sufficiently. For instance, two weeks post-operation, 50 per cent more pressure was needed to make the well-rested animals retract their paws than was needed to make the sleep-deprived mice do so. Bicca presented these findings at a meeting of the Society for Neuroscience in Washington DC on 13 November.
The team also found that sleep-deprived mice had more inflammatory cells at the site of their incision than those that had slept enough. This suggests that lack of sleep impairs the immune system鈥檚 ability to resolve inflammation, which is our body鈥檚 first line of defence against injury or illness, says Bicca. Inflammation also causes pain.
Whether these findings will translate to humans is unclear, says at Cleveland Clinic in Ohio. It is certainly possible, though, given the well-known link between sleep, inflammation and pain in humans, he says.
鈥淲ith our modern lifestyle, we are frequently not prioritising sleep,鈥� says Bicca. 鈥淭hat means most people facing surgery are [potentially] going to develop some sort of pain hypersensitivity and/or delayed tissue healing.鈥�
Healthcare facilities could lower this risk by minimising sleep disruptions, such as noise and light, says Cheng. 鈥淔or people with sleep disorders, like insomnia or obstructive sleep apnoea, sleep therapy should be part of the [pre-surgery] care to improve outcomes,鈥� he says.
