Cold showers are rarely fun. But if you suffer from insomnia, they can be downright painful.
A new study from the Norwegian Institute of Public Health in Bergen, Norway, found that people who struggle with insomnia or other sleep disruption issues also tend to have lower pain tolerances. It is the first study of its size to link these two conditions, as well as reveal that the association grows even stronger in people who also suffer from chronic pain as well as experience problematic sleep at least twice a week.
The team of Norwegian researchers, led by University of Bergen professor Børge Sivertsen, surveyed 10,400 adult participants. The survey included questions about whether or not participants struggled with any kind of sleep impairment, including insomnia, how long they slept each night on average and how long it typically took them to fall asleep. They also recorded whether the subjects dealt with chronic pain issues or psychological disorders like depression or anxiety.
Participants then underwent a well-known pain threshold test, the cold pressor test, during which they were forced to place their hand in a bath of ice water and leave it submerged for 106 seconds. The research team monitored how long each subject was able to withstand the cold water test, and then analyzed the relationships between their pain threshold performance and the personalized data gathered via the survey.
Only 32 percent of all participants were able to keep their hands submerged in the frigid water for the full duration of the test. But when the researchers looked specifically at those who suffered from insomnia, they found that they were more likely to take their hand out of the water early (42 percent) than those who didn't have insomnia (31 percent). They also noticed that the insomniac subjects exhibited increased pain sensitivity the more frequent and severe their sleeping problems were. Compared to non-insomnia participants, the rate of reduced pain tolerance was 52 percent higher for those who suffered insomnia at least twice a week and 24 percent higher for those with insomnia at least once a month.
The researchers found that psychological factors had a small but significant impact on pain tolerance as well. They also acknowledged a correlation between pain sensitivity and the time at which participants typically went to sleep each night. But surprisingly, the average length of sleep seemed to have no effect.
When looking closely at the subjects who previously reported issues with insomnia and chronic pain, Sivertsen and his team found that those people were more than twice as likely to have an increased pain sensitivity than subjects who dealt with only one (or none) of these ailments. Their report was published in PAIN, the journal of the International Association for the Study of Pain, this week.
"While there is clearly a strong relationship between pain and sleep, such that insomnia increases both the likelihood and severity of clinical pain, it is not clear exactly why this is the case," the researchers wrote. Since this is the first study to observe this link between insomnia and pain tolerance, and the first to determine that psychological factors like anxiety and depression could be contributors to that relationship, further research is required to look into the potential role neurotransmitters are playing in our experience of pain and sleep.
Prior research has significantly explored the detriments of sleep disorders like insomnia, finding that chronic disruptors of rest can compromise mental health later in life, harm your heart, and exacerbate psychological issues, to name a few issues. Some have also found chronic pain to be a preexisting condition causing a person's sleep troubles. It seems clear that these health issues are all linked -- it's just a matter of fully understanding the "why" behind their connections.