Abstract
Insomnia is a highly prevalent condition that predisposes to the development of many chronic pain disorders, with most of them showing a pronounced sexual dimorphism. We investigated whether prolonged exposure to experimental insomnia-like sleep disturbances affect spontaneous pain and pain sensitivity, and whether responses are modulated by sex. Twenty-four healthy participants (50% females, 28.3±5.9 years of age) underwent two 19-day long in-laboratory protocols in randomized order – an experimental sleep disturbance protocol consisting of repeated nights of short and disrupted sleep with intermittent nights of recovery sleep, and a sleep control protocol consisting of nights with an undisturbed 8-hour sleep. Spontaneous pain was assessed through electronic rating scales throughout the daytime and nighttime wake periods of the protocol. Pain sensitivity was assessed through pressure and heat pain threshold measures at every other day of the protocol. With respect to spontaneous pain, females responded with greater pain to sleep disturbances, while males responded with less pain (p<0.05 for condition*sex). With respect to pain sensitivity, females developed greater pressure pain sensitivity, while males develop greater pain sensitivity to heat pain (both p<0.05 for condition*sex) following the exposure to experimental sleep disturbances. Nighttime pain was greater than daytime pain and worsened across successive nights of sleep disturbances (p<0.05 for condition*day*daytime/nighttime), suggesting that pain management strategies may specifically target nighttime pain. In conclusion, sex strongly affects spontaneous pain and pain sensitivity responses to sleep disturbances, and these sex-differential responses may be one factor contributing to the overrepresentation of females in most chronic pain disorders.
Trial Registration: ClinicalTrials.gov NCT03377543.