BACKGROUND:Poor sleep, prevalent among cancer survivors, is associated with disrupted hormonal circadian rhythms and poor quality of life. Using a prospective research design, this study aimed to clarify the relationship between objective measures of sleep efficiency and sleep disruption with survival among women with advanced breast cancer. METHOD:We examined sleep quality and duration via wrist-worn actigraphy and sleep diaries for 3 days among 97 women in whom advanced breast cancer was diagnosed (age = 54.6 ± 9.8 years). Sleep efficiency was operationalized using actigraphy as the ratio of total sleep time to total sleep time plus wake after sleep onset. RESULTS:As hypothesized, better sleep efficiency was found to predict a significant reduction in overall mortality (hazard ratio [HR], 0.96; 95% confidence interval [CI], 0.94-0.98; P < 0.001) at median 6 y follow-up. This relationship remained significant (HR, 0.94; 95% CI, 0.91-0.97; P < 0.001) even after adjusting for other known prognostic factors (age, estrogen receptor status, cancer treatment, metastatic spread, cortisol levels, and depression). Secondary hypotheses were also supported (after adjusting for baseline prognostic factors) showing that less wake after sleep onset (HR, 0.41; 95% CI, 0.25-0.67; P < 0.001), fewer wake episodes, (HR, 0.93; 95% CI, 0.88-0.98; P = 0.007); and shorter wake episode duration (HR, 0.29; 95% CI, 0.14-0.58; P < 0.001) also contributed to reductions in overall mortality. CONCLUSIONS:These findings show that better sleep efficiency and less sleep disruption are significant independent prognostic factors in women with advanced breast cancer. Further research is needed to determine whether treating sleep disruption with cognitive behavioral and/or pharmacologic therapy could improve survival in women with advanced breast cancer.