EFFECTS OF SLEEP ON A HIGH HEAT CAPACITY MATTRESS ON SLEEP STAGES, EEG POWER SPECTRA, CARDIAC INTERBEAT INTERVALS AND BODY TEMPERATURES IN HEALTHY MIDDLE-AGED MEN

STUDY OBJECTIVES: This study deals with the question whether a slow (non-disturbing) reduction of core body temperature (CBT) during sleep increases sleep stage N3 and EEG slow wave energy (SWE) and leads to a slowing of heart rate in humans. METHODS: A high-heat capacity mattress was used to lower body temperatures in sleep and was compared to a conventional low-heat capacity mattress in a double-blinded fashion. Polysomnography was performed accompanied by measurements of skin-, core body- and mattress surface-temperatures, and heart rate. EEG power spectral analyses were carried out using Fast Fourier Transform. Inter-beat intervals were derived from the electrocardiogram. RESULTS: The high-heat capacity mattress led to a larger decline in CBT, mediated through higher heat conduction from the core via the proximal back skin onto the mattress together with reduced heart rate. These effects occurred together with a significant increase in sleep stage N3 and standardized slow wave energy (sSWE, 0.791-4.297Hz) accumulated in NREM sleep. In the 2nd half of the night sSWE increase was significantly correlated with body temperature changes, e.g. with CBT decline in the same phase. CONCLUSIONS: A high-heat capacity mattress subtly decreases CBT, leading to an increased amount of sleep stage N3 and of sSWE, as well as a slowing of heart rate.