Publications (14) View all
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Article: Quantitative exposure metrics for sleep disturbance and their association with breast cancer risk.
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ABSTRACT: PURPOSE: It has been acknowledged by those in the field of sleep epidemiology that the current measures of sleep used in many epidemiological studies do not adequately capture the complexity and variability of sleep. A number of ways to improve the measurement of sleep have been proposed. This study aimed to assess the relationship between novel 'sleep disturbance' metrics, as expanded measures of sleep, and breast cancer risk. METHODS: Data for this study were derived from a population-based case-control study conducted in Western Australia between 2009 and 2011. Participants completed a self-administered questionnaire that included questions about demographic, reproductive, and lifestyle factors in addition to questions on sleep. Four metrics of exposure to sleep disturbance (cumulative, average, duration, and peak) were developed. Unconditional logistic regression was used to examine the association between metrics of sleep disturbance and breast cancer risk. RESULTS: There was no evidence to support an association between any of the sleep disturbance metrics and breast cancer risk. Compared with the reference group of unexposed women, the fully adjusted ORs for cumulative sleep disturbance (harm) metric were as follows: 1st tertile 0.90 (95 % CI: 0.72-1.13); OR for the 2nd tertile 1.04 (95 % CI: 0.84-1.29); and OR for the 3rd tertile 1.02 (95 % CI: 0.82-1.27). CONCLUSIONS: This study found no association between several metrics of sleep disturbance and risk of breast cancer. Our experience with developing metrics of sleep disturbance may be of use to others in sleep epidemiology wishing to expand their scope of sleep measurement.Cancer Causes and Control 02/2013; · 2.88 Impact Factor -
Article: Self-reported Sleep Duration, Sleep Quality, and Breast Cancer Risk in a Population-based Case-Control Study.
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ABSTRACT: Breast cancer is one of the most commonly diagnosed invasive cancers. Established risk factors account for only a small proportion of cases. Previous studies have found reductions in sleep duration and quality in the general population over time. There is evidence to suggest a link between poor sleep and an increased risk of breast cancer. In this study, we investigated the relationship between breast cancer and sleep duration and quality in Western Australian women. Data were obtained from a population-based case-control study conducted from 2009 to 2011. Participants completed a self-administered questionnaire that included questions on sleep. Odds ratios and 95% confidence intervals were calculated using unconditional logistic regression. Sensitivity analysis for potential selection and misclassification bias was also conducted. We found no association between self-reported sleep duration on workdays and risk of breast cancer (for <6 hours, odds ratio (OR) = 1.05 (95% CI: 0.82, 1.33); for 6-7 hours, OR = 0.96 (95% CI: 0.80, 1.16); and for >8 hours, OR = 1.10 (95% CI: 0.87, 1.39), compared with the reference category of 7-8 hours' sleep). In addition, we found no association between sleep duration on nonworkdays, subjective sleep quality, or combined duration and quality and risk of breast cancer. This study does not provide evidence to support an association between self-reported sleep duration or quality and the risk of breast cancer.American journal of epidemiology 01/2013; · 5.59 Impact Factor -
Article: Girschik et al. Respond to "Sleep Duration and Breast Cancer"
American journal of epidemiology 01/2013; · 5.59 Impact Factor -
Article: Validation of self-reported sleep against actigraphy.
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ABSTRACT: Background: Self-report remains the most practical and cost-effective method for epidemiologic sleep studies involving large population-based samples. Several validated questionnaires have been developed to assess sleep, but these tools are lengthy to administer and may be impractical for epidemiologic studies. We examined whether a 3-item sleep questionnaire, similar to those typically used in epidemiologic studies, closely corresponded with objective measures of sleep as assessed using actigraphy monitoring.Methods: Eligible participants were Western Australian women aged 18 to 80 years. Participants completed a sleep questionnaire, wore a wrist actigraph for 7 nights, and completed a brief daily sleep log. Objective actigraphy measurements for 56 participants were summarized by mean and mode and compared with the subjective reports, using weighted kappa and delta.Results: Data collected from the questionnaire showed poor agreement with objectively measured sleep, with kappas ranging from -0.19 to 0.14.Conclusions: Our results indicate that sleep questions typically used in epidemiologic studies do not closely correspond with objective measures of sleep as assessed using actigraphy. The findings have implications for studies that have used such sleep questions. A means of appropriately measuring sleep as a risk factor in epidemiologic studies remains to be determined.Journal of Epidemiology 07/2012; 22(5):462-8. · 1.86 Impact Factor -
Article: Reliability of a sleep quality questionnaire for use in epidemiologic studies.
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ABSTRACT: The longer-term health impacts of poor sleep quality are of increasing interest, as evidence suggests that there are rising levels of sleep disturbance in the community. Studies have reported links between sleep quality and increased morbidity and mortality. However, the results of these studies are constrained by limitations in the measurement of sleep quality in epidemiologic studies. The Breast Cancer Environment and Employment Study (BCEES) has developed a sleep questionnaire that attempts to address some of the limitations of previous sleep questionnaires. The present study assessed the test-retest reliability of the sleep questionnaire used in the Breast Cancer Environment and Employment Study (BCEES). Subjects for this reliability study were women who were participating as controls in the BCEES study. Test-retest reliability was evaluated for individual items, using weighted kappa for categorical variables and intraclass correlation coefficients (ICC) and limits of agreement for continuous variables. Most sleep questions showed good agreement, ranging from 0.78 to 0.45. The ICC was 0.45 (95% CI 0.32-0.59) for lifetime sleep loss per year and 0.60 (95% CI 0.49-0.71) for symptom severity. The test-retest reliability of the general sleep questions was good, and future epidemiologic studies of sleep could reliably expand the number of assessed domains of sleep quality. However, reliability decreased as increasing detail was required from participants about specific periods of sleep disturbance, and changes to the questionnaire are warranted.Journal of Epidemiology 02/2012; 22(3):244-50. · 1.86 Impact Factor
