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| |  Insomnia in Women With Breast Cancer Linked to Heart Rate Dysregulation WESTCHESTER, Ill. -- October 15, 2008 -- Respiratory sinus arrhythmia (RSA) is a significant predictor of insomnia in women with breast cancer and confirmed that longer nocturnal wake episodes were associated with a flatter diurnal cortisol slope, according to a study in the October 15 issue of the Journal of Clinical Sleep Medicine. Results of this study confirmed a relationship between frequent awakenings and abnormal cortisol, rhythms in metastatic breast cancer, thus concluding that a disrupted cortisol rhythm may have serious medical implications in women with breast cancer. With the addition of demographics, disease severity and psychological variables, findings suggest that Vagal regulation, assessed via RSA, an important marker of parasympathetic tone, is the most consistent and significant predictor of sleep continuity disturbance.. "It was surprising to see that the strongest association was between a parasympathetic nervous system dysregulation and sleep problems even after we considered patients' age, their disease severity, type of treatment and psychological variables such as pain and stress," said the study's lead author, Oxana Palesh, PhD, University of Rochester Cancer Center, Rochester, New York The study included 99 women aged over 45 years who had metastatic breast cancer or recurrent breast cancer. Of the patients, 39 took antidepressants and 19 took medications specifically prescribed for treating disrupted sleep during study baseline. Participants collected saliva for cortisol measurement for 2 days, completed questionnaires, wore actigraphs to monitor their sleep-wake cycles for 3 days, and participated in the Trier Social Stress Task (TSST) approximately 1 to 2 weeks after the cortisol baseline collections. Demographic and cancer diagnosis history was collected from the women through self-report. Heart rate dysregulation during a stress task was associated with 4 objective measures of sleep disruption: sleep efficiency, wake after sleep onset, average number of awakenings and average length of waking episode. Estimates from 2 nights of actigraphy indicate that participants spent about 8 hours in bed and had wakefulness after sleep onset (WASO) of more than 71 minutes. They also had an average of 15 wake episodes each night with an average duration of 4.81 minutes. While demographics explained some portion of the development of sleep disruption, 4 of the 6 sleep parameters examined were best explained by low RSA. In healthy people, cortisol levels peak early in the morning and level-out by the end of the day. However, in one-third to two-thirds of women with metastatic breast cancer, circadian rhythms are disrupted and diurnal cortisol slopes are either flattened, have multiple peaks, or are elevated at the end of the day. According to Palesh, one of the best interventions for regulation of autonomic functioning is diaphragmatic breathing. Any number of stress management techniques would be effective, including biofeedback treatment, hypnosis, visualisation exercises, meditation, progressive muscle relaxation, and yoga. SOURCE: American Academy of Sleep Medicine
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