The relative importance of specific risk factors for insomnia in women treated for early-stage breast cancer

Background. Many individual risk factors for insomnia have been identified for women with a history of breast cancer. We assessed the relative importance of a wide range of risk factors for insomnia in this population. Methods: Two thousand six hundred and forty-five women <= 4 years post-treatment for Stage I (>= 1 cm)-IIIA breast cancer provided data on cancer-related variables, personal characteristics, health behaviors, physical health/symptoms, psychosocial variables, and the Women's Health Initiative-Insomnia Rating Scale (WHI-IRS; scores >= 9 indicate clinically significant insomnia). Results: Thirty-nine per cent had elevated WHI-IRS scores. In binary logistic regression, the variance in high/low insomnia group status accounted for by each risk factor category was: cancer-specific variables, 0.4% (n.s.); personal characteristics, 0.9% (n.s.); health behaviors, 0.6% (n.s.); physical health/symptoms, 13.4% (p<0.001); and, psychosocial factors, 11.4% (p<0.001). Insomnia was associated with worse depressive (OR = 1.32) and vasomotor symptoms (particularly night sweats) (OR = 1.57). Conclusion: Various cancer-specific, demographic, health behavior, physical health, and psychosocial factors have been previously reported as risk factors for insomnia in breast cancer. In our study (which was powered for simultaneous examination of a variety of variables), cancer-specific, health behavior, and other patient variables were not significant risk factors when in the presence of physical health and psychosocial variables. Only worse depressive and vasomotor symptoms were meaningful predictors. Copyright (C) 2007 John Wiley & Sons, Ltd.