After working a night shift, healthy people experience cold stimulus almost one third more painfully than before the night shift. After a night of rest, pain perception is back to normal again. This interaction between sleep and pain can play a relevant role in pain chronification. These are the core findings of a study conducted by the Department for Psychotherapy and Biopsychosocial Health at Danube University Krems to test pain perception of night shift workers with the aid of pain stimuli.

The body uses pain as a warning signal to protect the body from injury. However, how strongly people experience pain depends on many factors: do I cause the pain to myself or is it caused by another person? Do I associate the pain with a pleasant feeling such as during a massage, or with an unpleasant feeling? Pain perception is also controlled by psychic factors such as mood and pain memory.

A new study conducted by the Department for Psychotherapy and Biopsychosocial Health at Danube University Krems, in cooperation with the Department for Neurology at the University Clinic St. Pölten indicates that sleep deprivation also influences how we experience pain.

Pain perceived more strongly by a third
The study examined how pain was experienced by care staff at the University Clinic St. Pölten before and after the night shift. After the night shift, staff were noticeably more sensitive to pain, the same pain stimulus was rated almost 30 percent stronger than in a rested state. After a night of rest, pain sensitivity was back to normal.

“What the more intense pain experience is really due to – tiredness, mood or reduced pain inhibition - is still unclear,” says Univ.-Prof. Dr. med. univ. Christoph Pieh, head of the Department for Psychotherapy and Biopsychosocial Health at Danube University Krems.

Determining pain thresholds
The pain threshold and pain perception was tested with the aid of “pain stimuli.” To do this, a thermode was attached to the back of the test persons’ hands. A thermode is a device that stimulates heat and cold pain. In order to determine the test persons’ pain threshold, the thermode corrects the temperature downwards. The experiment began at 32°C and the temperature sank by 1°C every second. When the test persons began to experience the pain as unpleasant, they stopped the test by pressing a button. In the second experiment, the test persons had to rate a constant cold stimulus on a scale of 0 (not painful) to 100 (maximum imaginable pain.)

Search for other factors
This study is a further indication of the bilateral relationship between pain and sleep. “It’s like a cycle that mutually perpetuates itself. Sleep is disturbed by pain, and sleep deprivation makes people more sensitive to pain. Further studies will show what other factors influence pain perception, and whether night shift work is a possible pain chronification factor,” says Christoph Pieh, who led the study.

Publication: Pieh, C.; Jank, R.; Waiß, C.; Pfeifer, C.; Probst, T.; Lahmann, C.; Oberndorfer (Mai 2018): Night-shift work increases cold pain perception. In: Sleep Medicine: Vol. 54, S. 74-79.


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