The current study aimed to determine the frequency of sleep disturbances in women prior to adjuvant therapy for breast cancer (BCa), and whether greater sleep dysfunction uniquely predicts poorer functional outcomes. We assessed subjective sleep reports and associated them with multiple indicators of psychosocial adaptation in 240 women with Stage I-III BCa before they had begun adjuvant treatment. The average global score on the Pittsburgh Sleep Quality Index (PSQI) was 8.49 (SD=4.16); 54% scoring above the suggested adjusted cutoff for cancer populations of 8.0. Controlling for various medical, sociodemographic, and psychosocial covariates, multiple regression analyses revealed that higher global PSQI score was significantly associated with poorer functional well-being, greater fatigue intensity, greater disruptions in social interactions, and lower positive states of mind. Specifically, a poorer 'sleep efficiency' PSQI component was associated with poorer functional quality of life and the SIP-Social Interactions subscale, while a poorer 'sleep quality' (SQ) PSQI component was associated with all of the outcomes except for the SIP-Recreations and Pastimes subscale. Results indicate consistent associations between a clinical indicator of sleep dysfunction, particularly those subscales of the PSQI comprising the 'SQ' component, and multiple indicators of psychosocial adaptation among women treated for BCa, independent of anxiety and depression, and suggest the value of comprehensive psychosocial interventions that consider sleep problems. (c) 2009 John Wiley & Sons, Ltd.
