Does sleep differ among patients with common musculoskeletal pain disorders?

Most patients with chronic musculoskeletal pain report poor-quality sleep. The impact of chronic pain on sleep can be described as a vicious circle with mutual deleterious influences between pain and sleep-associated symptoms. It is difficult, however, to extract quantitative or consistent and specific sleep variables (eg, total sleep time, slow-wave sleep, sleep stage duration) that characterize the pain-related disruption of sleep. Comorbidity (eg, fatigue; depression; anxiety, sleep, movement, or breathing disorders) often confounds the reading and interpretation of sleep traces. Furthermore, many other methodologic issues complicate our ability to generalize findings (low external validity) to first-line medicine. Because sleep alterations in common musculoskeletal pain are neither specific nor pathognomonic, the aim is to provide a critical overview of the current understanding of pain and sleep interaction, discussing evidence-based and empiric knowledge that should be considered in further research and clinical applications.