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Introduction: Sleep disruption affects biological processes that facilitate carcinogenesis. This retrospective cohort study used de-identified data from the Veterans Administration (VA) electronic medical record system to test the hypothesis that patients with diagnosed sleep disorders had an increased risk of prostate, breast, colorectal, or other cancers (1999-2010, N=663,869). This study builds upon existing evidence by examining whether patients with more severe or longer-duration diagnoses were at a greater risk of these cancers relative to those with a less severe or shorter duration sleep disorder. Methods: Incident cancer cases were identified in the VA Tumor Registry and sleep disorders were defined by International Classification of Sleep Disorder codes. Analyses were performed using extended Cox regression with sleep disorder diagnosis as a time-varying covariate. Results: Sleep disorders were present among 56,055 eligible patients (8% of the study population); sleep apnea (46%) and insomnia (40%) were the most common diagnoses. There were 18,181 cancer diagnoses (41% prostate, 12% colorectal, 1% female breast, 46% other). The hazard ratio (HR) for a cancer diagnosis was 1.45 (95% confidence interval [CI]: 1.37, 1.54) among those with any sleep disorder, after adjustment for age, sex, state of residence, and marital status. Risks increased with increasing sleep disorder duration (short [<1-2 years] HR: 1.04 [CI: 1.03-1.06], medium [>2-5 years] 1.23 [1.16-1.32]; long [>5-12 years] 1.52 [1.34-1.73]). Risks also increased with increasing sleep disorder severity using cumulative sleep disorder treatments as a surrogate exposure; African Americans with more severe disorders had greater risks relative to those with fewer treatments and other race groups. Results among patients with only sleep apnea, insomnia, or another sleep disorder were similar to those for all sleep disorders combined. Discussion: The findings are consistent with other studies indicating that sleep disruption is a cancer risk factor. Optimal sleep and appropriate sleep disorder management are modifiable risk factors that may facilitate cancer prevention.
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BACKGROUND: Although much has been done to examine those factors associated with higher mortality among African American women, there is a paucity of literature that examines disparities among rural African Americans in South Carolina. The purpose of this investigation was to examine the association of race and mortality among breast cancer patients in a large cohort residing in South Carolina for which treatment regimens are standardized for all patients. METHODS: Subjects included 1209 women diagnosed with breast cancer between 2000 and 2002 at a large, local hospital containing a comprehensive breast center. Kaplan-Meier survival curves were calculated to determine survival rates among African American and European American women, stratified by disease stage or other prognostic characteristics. Adjusting for various characteristics, Cox multivariate survival models were used to estimate the hazard ratio (HR). RESULTS: The 5-year overall all-cause mortality survival proportion was â¼78% for African American women and â¼89% for European American women, P < 0.01. In analyses of subpopulations of women with identical disease characteristics, African American women had significantly higher mortality than European American women for the same type of breast cancer disease. In multivariate models, African American women had significantly higher mortality than European American women for both breast cancer-specific death (HR, 2.41; 95% confidence interval [CI], 1.21-4.79) and all-cause mortality (HR, 1.42; 95% CI, 1.06-1.89). CONCLUSIONS: African American women residing in rural South Carolina had lower survival for breast cancer even after adjustment for disease-related prognostic characteristics. These findings support health interventions among African American breast cancer patients aimed at tertiary prevention strategies or further down-staging of disease at diagnosis.