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 < or =4 years post-treatment for Stage I (> or =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 > or =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.