Effects of bedtime periocular and posterior cervical cutaneous warming on sleep status in adult male subjects: a preliminary study

Abstract

Appropriate warming of the periocular or posterior cervical skin has been reported to induce autonomic or mental relaxation in humans. To clarify the effects of cutaneous warming on human sleep, eight male subjects with mild sleep difficulties were asked to try three experimental conditions at home, each lasting for 5 days, in a cross-over manner: warming of the periocular skin with a warming device for 10 min before habitual bedtime, warming of the posterior cervical skin with a warming device for 30 min before habitual bedtime, and no treatment as a control. The warming device had a heat- and steam-generating sheet that allowed warming of the skin to 40 °C through a chemical reaction with iron. Electroencephalograms (EEGs) were recorded during nocturnal sleep using an ambulatory EEG device and subjected to spectral analysis. All the participants reported their sleep status using a visual analog scale. We found that warming of the periocular or posterior cervical skin significantly improved subjective sleep status relative to the control. The EEG delta power density in the first 90 min of the sleep episode was significantly increased under both warming of the periocular or posterior cervical skin relative to the control. These results suggest that warming of appropriate skin regions may have favorable effects on subjective and objective sleep quality.

Periocular skin warming promotes body heat loss and sleep onset: a randomized placebo-controlled study

“…Our results are comparable with our previous findings that periocular warming before bedtime improved subjective sleep initiation and enhanced delta power in the first 90-min period of the nocturnal sleep 23 . The results obtained through qualitive and quantitative EEG analyses in the present study clearly indicated that periocular skin warming accelerated and deepened non-rapid eye movement (NREM) sleep.…”

“…However, it is not clear which location on the human skin is most effective to promote sleep. Previous 22 , 23 studies and present study have showed that appropriate periocular skin warming has favorable effects on sleep. We postulate that the periocular skin region might be regarded as one closest regions of the eyes which is directly connected to the brain.…”

“…Therefore, further study is required to clarify the effects of periocular warming on age- or sex-related thermoregulatory functions. Second, although our previous report suggested an improvement in subjective sleep initiation by periocular skin warming 23 , the present results alone may not sufficiently reveal the effects of periocular warming on nocturnal sleep because this study examined the effects of periocular warming only during the ascending portion of circadian core body temperature fluctuation, in the daytime. It is necessary to verify whether periocular skin warming has favorable effects on sleep during the night, when circadian core body temperature fluctuation shows descending trend.…”

“…Fifth, this study was conducted using a warming eye mask, which maintained the periocular skin temperature at 38–40°C for approximately 20 min. However, the duration of warming in the previous study was approximately 10 minutes 23 . Therefore, further investigation on applying the warming eye mask for varying durations will be necessary to clarify the relationship of warming duration and sleep.…”

“…We have previously developed a disposable heat- and steam generating sheet (HSG-sheet) which can safely and easily manipulate the local skin temperature (e.g., the periocular 20 – 24 , neck 23 , and abdominal 25 skin region) at home. Our studies has reported that periocular skin warming before bedtime improved the subjective sleep quality 22 , 23 and increased the electroencephalography (EEG) delta power 23 during the first half of the sleep episode in adults with mild difficulty falling asleep. Recently, we have demonstrated that periocular skin warming increased the distal skin temperature in the hand and foot, which indicated enhancement of the physiological heat loss process 24 .…”