Protective Effect of a High Heat Conductivity Mattress Topper on Sleep During Heat Night

Environmental high temperatures can strongly affect sleep. Our aim was to assess the protective effect of a High Heat Conductivity Mattress topper (HHCM) on sleep duration and quality during one night's exposure to heat. HHCM efficacy was studied in a randomised double-blind crossover design in fifteen healthy young active subjects by overnight polysomnography in a temperature-controlled sleep laboratory, during 4 nights: 2 nights at 22°C (HHCM and Control Mattress, CM) and 2 nights at 32°C (HHCM and CM). Core body temperature (CBT), skin, room and mattress toppers surface temperatures were continuously recorded. We observed interactions between temperature and mattress conditions. At 22°C, we did not show any beneficial effect of HHCM compared to CM on sleep duration, but a longer N3 sleep stage duration (p = 0.03) and higher slow oscillation spectral density (p = 0.03). Heat night exposure (32°C) induced a decrease in total sleep time (TST) (-24.8 ± 7.1 min, p = 0.02), rapid eye movement (REM) duration (p = 0.03), sleep efficiency (p = 0.04), delta power spectral density (p = 0.03) and an increase of wake after sleep onset (p = 0.03) and transition between stages rate (p = 0.02). At 32°C, in comparison to CM, HHCM induced higher TST (+21.4 ± 16.1 min, p = 0.04), sleep efficiency (p = 0.04), REM duration (p = 0.03), and lower awakening duration (p = 0.03). These effects were associated with lower skin temperature and CBT. In conclusion, HHCM improves sleep quality and has a protective effect on CBT and sleep patterns during heat exposure in active healthy subjects. It could be a countermeasure for promoting sleep in particular during heat waves.