Objective: The specific link between obstructive sleep apnea (OSA) and pain is unknown, but it has been hypothesized that OSA patients are hyperalgesic because of fragmented sleep and hypoxemia that enhance sensitivity to pain, promote inflammation, and increase spontaneous pain. We conducted a systematic review of the literature assessing whether OSA is a risk factor for subjective pain intensity and experimental pain tolerance and threshold.
Design/participants: A search of published studies in English in MEDLINE, PubMed, Embase, and the Cochrane Database of Systematic Reviews from database inception through May 2017 was performed. Search terms included "sleep apnea," "continuous positive airway pressure," "CPAP," "pain," and "chronic pain."
Methods: We included any study that reported an association between OSA or polysomnogram assessments with pain outcomes or reported the effect of CPAP on pain outcomes. Controlled studies, cohort studies, and case-control studies were included.
Results: We identified 448 studies from PubMed and 959 studies from Embase, giving a combined 1,333 studies after removing duplicates. After detailed selection, 28 articles were reviewed in full and 12 met study inclusion criteria. Whereas several studies found an association between OSA and pain intensity or experimental pain, there was considerable variability among study outcomes. Delivery of CPAP may improve pain and decrease opioid use, although the exact nature of the relationship between pain and the various pathophysiologic components of OSA is unclear.
Conclusions: This systematic review summarizes the current evidence for the association of OSA and pain outcomes. Further research is needed to identify the differential effects of nocturnal hypoxemia and fragmented sleep on pain intensity. Clinicians might consider screening patients with chronic pain for OSA.