Previous work has demonstrated a link between restricted sleep and risk indicators for cardiovascular and metabolic disease, such as levels of cortisol, lipids, and glucose. The present study sought to identify relations between polysomnographic measures of disturbed sleep (frequency of arousals from sleep, total sleep time, and sleep efficiency) and a number of such indicators. A second purpose was to relate the number of arousals to mood, stress, work characteristics, and other possible predictors in daily life.
Twenty-four people (10 men, 14 women; mean age 30 years), high vs. low on burnout, were recruited from a Swedish IT company. Polysomnographically recorded sleep was measured at home before a workday. Blood pressure, heart rate, morning blood sample, and saliva samples of cortisol were measured the subsequent working day. They were also recorded for diary ratings of sleep and stress, and a questionnaire with ratings of sleep, stress, work conditions, and mood was completed.
A stepwise regression analysis using sleep parameters as predictors brought out number of arousals as the best predictor of morning cortisol (serum and saliva), heart rate, systolic and diastolic blood pressure, total cholesterol, high-density lipoprotein (HDL)-, low-density lipoprotein (LDL)-cholesterol, and LDL/HDL-ratio. Work stress/unclear boundaries between work and leisure time was the best predictor of arousals among the stress variables.
Consistent with sleep restriction experiments, sleep fragmentation was associated with elevated levels of metabolic and cardiovascular risk indicators of stress-related disorders. Number of arousals also seems to be related to workload/stress.
ABP = ambulatory blood pressure; DBP = diastolic blood pressure; EEG = electroencephalogram; EMG = electromyographic; EOG = electro-oculogram; HAD = hospital anxiety and depression scale; PSG = polysomnography; SBP = systolic blood pressure; SMBQ = Shirom Melamed burnout questionnaire; TST = total sleep time; WHR = waist to hip ratio.