Correlation between rest-activity rhythm and survival in cancer patients experiencing pain

The purpose of this study was to investigate the influence of rest-activity rhythm on the survival of cancer patients. This study collected data related to cancer patients experiencing pain who had been hospitalized for treatment between August 2006 and October 2007. Data included the Karnofsky Performance Status Index as a representation of functional condition as well as the Brief Pain Inventory and the Pittsburgh Sleep Quality Index. Actigraphic methods were used to record the dichotomy index (I<O) of patients' rest-activity rhythms over periods of three consecutive days. Patients were closely followed until 31 July 2013. Results were analyzed using Kaplan-Meier survival analysis, log-rank testing and Cox proportional hazards regression analysis to evaluate whether alterations in the rest-activity rhythm affected the survival rate of the patients. Of the 68 hospitalized cancer patients experiencing pain at the time of admission, 51 subsequently died within the study period. A significant difference was observed in the survival curves between the regular I<O group and the disrupted I<O group (log rank=7.942, p=0.005). A multivariable proportional hazard model was used for analysis of overall survival, revealing that the risk of death within the study period among patients with disrupted I<O was 4.59 times higher than that of patients with regular I<O (95% CI: 1.92-10.96, p=0.001). Among patients with poor performance status, the risk of death among patients with disrupted I<O was 8.68 times higher than that of patients with regular I<O (95% CI: 2.50-30.09, p=0.001). Disruptions in rest-activity rhythm were negatively correlated with the survival of hospitalized cancer patients experiencing pain. Effects were particularly pronounced in cancer patients with poor performance status.