A longitudinal study of sleep and leukemia incidence among postmenopausal women

We sought to assess the relationship between sleep duration, sleep disturbance and leukemia incidence among postmenopausal women. This study included 130343 postmenopausal women 50-79 years, who were enrolled in the Women’s Health Initiative during 1993-1998. Variables of self-reported, typical sleep duration and sleep disturbance were obtained at baseline by questionnaire, and the sleep disturbance level was defined according to the WHI Insomnia Rating Scale (WHIIRS). WHIIRS 0-4, 5-8 and 9-20 comprised 37.0%, 32.6% and 30.4% of all women, respectively. After an average of 16.4 years (2,135,109 cumulative person-years) of follow-up, 930 of the participants were identified with incident leukemia in this study. Compared to women with the lowest sleep disturbance (WHIIRS 0-4), women having higher sleep disturbance level (WHIIRS 5-8 or 9-20) had a 22% (95% CI: 1.04-1.43) and 18% (95% CI: 1.00-1.40) excess risk of leukemia respectively, after multivariable adjustment. A significant dose-response trend was found for sleep disturbance and leukemia risk (P for trend 0.048). In addition, women with highest sleep disturbance had a higher risk of myeloid leukemia (WHIIRS 9-20 vs WHIIRS 0-4, HR: 1.39, CI: 1.05-1.83). Higher sleep disturbance level was associated with increased risk of leukemia, especially for myeloid leukemia among postmenopausal women.