Creating a sleep-permissive condition using bed warming

Abstract

Recent studies showed that mild skin warming, without hampering core body temperature decline, improved sleep onset and promoted slow wave sleep and sleep maintenance [1,2]. We were challenged to translate these findings, originating from fully controlled laboratory studies, into a prototype for a home-applicable, sleep promoting solution. As a suitable solution, a multi-zoned low power feedback controlled electric heating blanket was developed. It was hypothesized that mild bed warming will increase skin temperature – without affecting core body temperature – and subsequently affect sleep. 8 healthy sleepers (4 males) were studied in the sleep experience laboratory for two nights. Participants slept one night in a bed warmed to 34°C (W) and one night in a non-warmed bed (N). Bed temperature was controlled via a multi-zoned low power feedback controlled electric heating blanket developed at our technical department. Skin temperature was calculated by means of temperature sensors placed on 9 standard body positions. Sleep was measured using PSG and questionnaires. Relative amount of Wake (N: 2.5 ± 0.6% vs. W: 0.9 ± 0.2%; p = 0.023) and S1 (N: 3.7 ± 0.7% vs. W: 2.4 ± 0.3%; p = 0.043) was suppressed whilst sleeping in the warmed bed. Furthermore, SOL was shorter (N: 16.8 ± 4.4 min vs. W: 10.4 ± 4.1 min; p = 0.009) and the sleep efficiency (N: 94.5 ± 0.9% vs. W: 97.0 ± 0.8%; p = 0.004) was higher in the bed warming condition. The reduction in the relative amount of Wake was also reflected in the subjective reports on wakefulness (N: 16.8 ± 7.6 min vs. W: 6.3 ± 3.6 min; p = 0.034). Surprisingly, no significant differences in skin temperature were observed between the bed warming condition and the control condition. In the present study, we showed that feedback-controlled bed warming improved sleep, even without observing an overall higher mean skin temperature. Since we did not replicate warming effects on SWS sleep [2], we concluded that mild bed warming (without affecting skin temperature) is creating a sleep-permissive condition rather than a sleep promoting condition. These findings show that the use of temperature manipulations to affect sleep go beyond well-controlled laboratory settings; bed warming is an affordable and easy to apply sleep aid that might be of use in a clinical/therapeutic setting as well. [1] Raymann RJ et al., AJP, 2005;1589–97. [2] Raymann RJ et al., Brain, 2008;500–13.