Poor sleep can heighten sensitivity to pain, research suggests.
Scientists conducted an experiment in which volunteers were "tortured" after sleeping well or badly, with the 25 young participants having uncomfortable levels of heat applied to their legs.
They rated their thermal pain on a scale of one to 10, generally reporting discomfort about 44C.
After having their baseline pain sensitivity recorded following a full night's sleep, the volunteers underwent the same ordeal but this time when they were sleep-deprived.
Generally, they reported feeling pain sooner, typically about 41.6C.
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Researcher Adam Krause, from the University of California at Berkeley, said: "Across the group, they were feeling discomfort at lower temperatures, which shows that their own sensitivity to pain had increased after inadequate sleep.
"The injury is the same but the difference is how the brain assesses the pain without sufficient sleep."
The findings, published in the Journal of Neuroscience, suggest sleep must be placed "close to the centre of patient care", especially in hospitals, the scientists said.
Brain scans conducted alongside the tests showed sleep loss not only amplified pain-sensing regions of the brain but blocked pain-suppressing centres.
An online survey carried out among 230 adults of all ages suggested even minor shifts in sleep and wake patterns affected pain sensitivity.
"The results clearly show that even very subtle changes in nightly sleep, reductions that many of us think little of in terms of consequences, have a clear impact on your next day pain burden," said Krause, a PhD student who was the study's lead author.
