Lead author Edward J. Stepanski of the Accelerated Community Oncology Research Network in Memphis, said the relationship between pain and sleep often has been assumed to be reciprocal. In the present study, a model of reciprocal causation could not be fit to the data, and models in which pain caused trouble sleeping did not fit as well as the model in which trouble sleeping caused pain.
"We believed we would find a bi-directional relationship between insomnia and pain, but instead we found that trouble sleeping was more likely a cause, rather than a consequence, of pain in patients with cancer," Stepanski said in a statement.
The researchers report that increases in depressed mood also led to increased ratings of pain.
The study included demographic, clinical and patient-reported outcomes data from 11,445 cancer patients with an average age of 61.5 years undergoing treatment in Memphis. The majority of participants -- 74 percent -- were female and 25 percent of study subjects had received chemotherapy in the last 30 days.
The findings are published in the Journal of Clinical Sleep Medicine.
